The physician treating the acutely ill febrile patient must be able to recognize infections that require emergent attention. If such infections are not adequately evaluated and treated at initial presentation, the opportunity to alter an adverse outcome may be lost. In this chapter, the clinical presentations of and approach to patients with relatively common infectious disease emergencies are discussed. These infectious processes and their treatments are discussed in detail in other chapters.
APPROACH TO THE PATIENT Acute Febrile Illness
Before the history is elicited and a physical examination is performed, an immediate assessment of the patient’s general appearance can yield valuable information. The perceptive physician’s subjective sense that a patient is septic or toxic often proves accurate. Visible agitation or anxiety in a febrile patient can be a harbinger of critical illness. HISTORY
Presenting symptoms are frequently nonspecific. Detailed questions should be asked about the onset and duration of symptoms and about changes in severity or rate of progression over time. Host factors and comorbid conditions may increase the risk of infection with certain organisms or of a more fulminant course than is usually seen. Lack of splenic function, alcoholism with significant liver disease, IV drug use, HIV infection, diabetes, malignancy, organ transplantation, and chemotherapy all predispose to specific infections and frequently to increased severity. The patient should be questioned about factors that might help identify a nidus for invasive infection, such as recent upper respiratory tract infections, influenza, or varicella; prior trauma; disruption of cutaneous barriers due to lacerations, burns, surgery, body piercing, or decubiti; and the presence of foreign bodies, such as nasal packing after rhinoplasty, tampons, or prosthetic joints. Travel, contact with pets or other animals, or activities that might result in tick or mosquito exposure can lead to diagnoses that would not otherwise be considered. Recent dietary intake, medication use, social or occupational contact with ill individuals, vaccination history, recent sexual contacts, and menstrual history may be relevant. Pregnancy might increase the risk and severity of some illnesses, such as influenza, or increase the risk of significant morbidity for the fetus, as in Listeria or Zika virus infection. A review of systems should focus on any neurologic signs or sensorium alterations, rashes or skin lesions, and focal pain or tenderness and should also include a general review of respiratory, gastrointestinal, or genitourinary symptoms. PHYSICAL EXAMINATION
A complete physical examination should be performed, with special attention to several areas that are sometimes given short shrift in routine examinations. Assessment of the patient’s general appearance and vital signs, skin and soft tissue examination, and the neurologic evaluation are of particular importance.
The patient may appear either anxious and agitated or lethargic and apathetic. Fever is usually present, although elderly patients and compromised hosts (e.g., patients who are uremic or cirrhotic and those who are taking glucocorticoids or nonsteroidal anti-inflammatory drugs) may be afebrile despite serious underlying infection. Critically ill patients may be hypothermic, with a high risk of organ failure and mortality. Measurement of blood pressure, heart rate, and respiratory rate helps determine the degree of hemodynamic and metabolic compromise. The patient’s airway must be evaluated to rule out the risk of obstruction from an invasive oropharyngeal infection.
The etiologic diagnosis may become evident in the context of a thorough skin examination (Chap. 16). Petechial rashes are typically seen with meningococcemia or Rocky Mountain spotted fever (RMSF; see Fig. A1-16); erythroderma is associated with toxic shock syndrome (TSS) and drug fever. The soft tissue and muscle examination is critical. Areas of erythema or duskiness, edema, and tenderness may indicate underlying necrotizing fasciitis, myositis, or myonecrosis. The neurologic examination must include a careful assessment of mental status for signs of early encephalopathy. Evidence of nuchal rigidity or focal neurologic findings should be sought. DIAGNOSTIC WORKUP
After a quick clinical assessment, diagnostic material should be obtained rapidly and antibiotic and supportive treatment begun. Blood (for cultures; baseline complete blood count with differential; measurement of serum electrolytes, blood urea nitrogen, serum creatinine, and serum glucose; and liver function tests) can be obtained at the time an IV line is placed and before antibiotics are administered. The blood lactate concentration also should be measured. Three sets of blood cultures should be performed for patients with possible acute endocarditis. Blood smears from patients at risk for severe parasitic disease, such as malaria or babesiosis (Chaps. 219, 220, and A6), must be examined for the diagnosis and quantitation of parasitemia. Blood smears may also be diagnostic in ehrlichiosis and anaplasmosis.
Patients with possible meningitis should have cerebrospinal fluid (CSF) drawn before the initiation of antibiotic therapy. Focal findings, depressed mental status, or papilledema should be evaluated by brain imaging prior to lumbar puncture, which, in this setting, could initiate herniation. Antibiotics should be administered before imaging but after blood for cultures has been drawn. If CSF cultures are negative, blood cultures will provide the diagnosis in 50–70% of cases. Molecular diagnostic techniques (e.g., broad-range 16S rRNA gene polymerase chain reaction testing for bacterial meningitis pathogens) are of increasing importance in the rapid diagnosis of life-threatening infections.
Focal abscesses necessitate immediate CT or MRI as part of an evaluation for surgical intervention. Other diagnostic procedures, such as wound cultures, should not delay the initiation of treatment for more than minutes. Once emergent evaluation, diagnostic procedures, and (if appropriate) surgical consultation (see below) have been completed, other laboratory tests can be conducted. Appropriate radiography, computed axial tomography, MRI, urinalysis, measurement of the erythrocyte sedimentation rate and/or C-reactive protein level, procalcitonin monitoring, and transthoracic or transesophageal echocardiography all may prove important.
TREATMENT The Acutely Ill Patient
In the acutely ill patient, empirical antibiotic therapy is critical and should be administered without undue delay in addition to fluid resuscitation and vasopressor support as needed. Increased prevalence of antibiotic resistance in community-acquired bacteria must be considered when antibiotics are selected. Table 117-1 lists first-line empirical regimens for infections considered in this chapter. In addition to the rapid initiation of antibiotic therapy, several of these infections require urgent surgical attention. Neurosurgical evaluation for subdural empyema, otolaryngologic surgery for possible mucormycosis, and cardiothoracic surgery for critically ill patients with acute endocarditis are as important as antibiotic therapy. For infections such as necrotizing fasciitis and clostridial myonecrosis, rapid surgical intervention supersedes other diagnostic or therapeutic maneuvers.
Adjunctive treatments may reduce morbidity and mortality rates and include dexamethasone for bacterial meningitis or IV immunoglobulin for TSS and necrotizing fasciitis caused by group A Streptococcus. Adjunctive therapies should usually be initiated within the first hours of treatment; however, dexamethasone for bacterial meningitis must be given before or at the time of the first dose of antibiotic. Glucocorticoids can also be harmful, sometimes resulting in worse outcomes—e.g., when given in the setting of cerebral malaria or viral hepatitis.
TABLE 117-1Empirical Treatment for Common Infectious Disease Emergenciesa ||Download (.pdf) TABLE 117-1 Empirical Treatment for Common Infectious Disease Emergenciesa
|CLINICAL SYNDROME ||POSSIBLE ETIOLOGIES ||TREATMENT ||COMMENTS ||SEE CHAP(S). |
|Sepsis without a Clear Focus |
|Septic shock ||Pseudomonas spp., gram-negative enteric bacilli, Staphylococcus spp., Streptococcus spp. || |
Vancomycin (15 mg/kg q12h)b plus gentamicin (5 mg/kg per day)
Piperacillin/tazobactam (3.375–4.5 g q6h) or cefepime (2 g q8h)c
|Empirical therapy should be tailored to local resistance patterns. Adjust treatment when culture data become available. ||142, 143, 156, 159, 297 |
|Overwhelming post-splenectomy sepsis ||Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis ||Ceftriaxone (2 g q12h) plus vancomycin (15 mg/kg q12h)b ||If a β-lactam-sensitive strain is identified, vancomycin can be discontinued. ||297 |
|Babesiosis ||Babesia microti (U.S.), B. divergens (Europe) ||Clindamycin (600 mg q8h) plus quinine (650 mg q8h) ||Atovaquone and azithromycin can be used in less severe disease and are associated with fewer side effects. Treatment with doxycycline (100 mg bid) for potential co-infection with Borrelia burgdorferi or Anaplasma spp. may be prudent. ||217, 220 |
|Sepsis with Skin Findings |
|Meningococcemia ||N. meningitidis ||Penicillin (4 mU q4h) or ceftriaxone (2 g q12h) ||Ceftriaxone eradicates nasopharyngeal carriage of the organism. Close contacts require chemoprophylaxis with rifampin (600 mg q12h for 2 days) or ciprofloxacin (a single dose, 500 mg). ||150 |
|Rocky Mountain spotted fever (RMSF) ||Rickettsia rickettsii ||Doxycycline (100 mg bid) ||If both meningococcemia and RMSF are being considered, use ceftriaxone (2 g q12h) plus doxycycline (100 mg bid). If RMSF is diagnosed, doxycycline is the proven superior agent. ||182 |
|Purpura fulminans ||S. pneumoniae, H. influenzae, N. meningitidis ||Ceftriaxone (2 g q12h) plus vancomycin (15 mg/kg q12h)b ||If a β-lactam-sensitive strain is identified, vancomycin can be discontinued. ||141, 150, 152, 297 |
|Erythroderma: toxic shock syndrome ||Group A Streptococcus, Staphylococcus aureus ||Vancomycin (15 mg/kg q12h)b plus clindamycin (600 mg q8h ||If a penicillin- or oxacillin-sensitive strain is isolated, these agents are superior to vancomycin (penicillin, 2 mU q4h; or oxacillin, 2 g IV q4h). The site of toxigenic bacteria should be debrided; IV immunoglobulin can be used in severe cases.d ||142, 143 |
|Sepsis with Soft Tissue Findings |
|Necrotizing fasciitis ||Group A Streptococcus, mixed aerobic/anaerobic flora, CA-MRSAe ||Vancomycin (15 mg/kg q12h)b plus clindamycin (600 mg q8h) plus gentamicin (5 mg/kg per day) ||Urgent surgical evaluation is critical. Adjust treatment when culture data become available. ||124, 142, 143 |
|Clostridial myonecrosis ||Clostridium perfringens ||Penicillin (2 mU q4h) plus clindamycin (600 mg q8h) ||Urgent surgical evaluation is critical. ||149 |
|Neurologic Infections |
|Bacterial meningitis ||S. pneumoniae, N. meningitidis ||Ceftriaxone (2 g q12h) plus vancomycin (15 mg/kg q12h)b ||If a β-lactam–sensitive strain is identified, vancomycin can be discontinued. If the patient is >50 years old or has comorbid disease, add ampicillin (2 g q4h) for Listeria coverage. Dexamethasone (10 mg q6h for 4 days) improves outcome in adults with meningitis (especially pneumococcal). ||133 |
|Brain abscess, suppurative intracranial infections ||Streptococcus spp., Staphylococcus spp., anaerobes, gram-negative bacilli ||Vancomycin (15 mg/kg q12h)b plus metronidazole (500 mg q8h) plus ceftriaxone (2 g q12h) ||Urgent surgical evaluation is critical. If a penicillin- or oxacillin-sensitive strain is isolated, these agents are superior to vancomycin (penicillin, 4 mU q4h; or oxacillin, 2 g q4h). ||133 |
|Cerebral malaria ||Plasmodium falciparum ||Artesunate (2.4 mg/kg IV at 0, 12, and 24 h; then once daily)f or quinine (IV loading dose of 20 mg salt/kg; then 10 mg/kg q8h) ||Do not use glucocorticoids. Use IV quinidine if IV quinine is not available. During IV quinidine treatment, blood pressure and cardiac function should be monitored continuously and blood glucose periodically. ||217, 219 |
|Spinal epidural abscess ||Staphylococcus spp., gram-negative bacilli || |
Vancomycin (15 mg/kg q12h)b
Piperacillin/tazobactam (3.375–4.5 g q6h) or cefepime (2 g q8h)c
|Surgical evaluation is essential. If a penicillin- or oxacillin-sensitive strain is isolated, these agents are superior to vancomycin (penicillin, 4 mU q4h; or oxacillin, 2 g q4h). ||434 |
|Focal Infections |
|Acute bacterial endocarditis ||S. aureus, β-hemolytic streptococci, HACEK group,g Neisseria spp., S. pneumoniae ||Ceftriaxone (2 g q12h) plus vancomycin (15 mg/kg q12h)b ||Adjust treatment when culture data become available. Surgical evaluation is essential. ||123 |
The infections considered below according to common clinical presentation can have rapidly catastrophic outcomes, and their immediate recognition and treatment can be life-saving. Recommended empirical therapeutic regimens are presented in Table 117-1.
SEPSIS WITHOUT AN OBVIOUS FOCUS OF PRIMARY INFECTION
Patients initially have a brief prodrome of nonspecific symptoms and signs that progresses quickly to hemodynamic instability with hypotension, tachycardia, tachypnea, respiratory distress, and altered mental status. Disseminated intravascular coagulation (DIC) with clinical evidence of a hemorrhagic diathesis is a poor prognostic sign.
Patients with bacteremia leading to septic shock may have a primary site of infection (e.g., pneumonia, pyelonephritis, or cholangitis) that is not evident initially (See also Chap. 297). Elderly patients with comorbid conditions, hosts compromised by malignancy and neutropenia, and patients who have recently undergone a surgical procedure or hospitalization are at increased risk for an adverse outcome. Gram-negative bacteremia with organisms such as Pseudomonas aeruginosa or Escherichia coli and gram-positive infection with organisms such as Staphylococcus aureus (including methicillin-resistant S. aureus [MRSA]) or group A streptococci can present as intractable hypotension and multiorgan failure. Treatment can usually be initiated empirically on the basis of the presentation, host factors (Chap. 297), and local patterns of bacterial resistance. Outcomes are worse when antimicrobial treatment is delayed or when the responsible pathogen ultimately proves not to be susceptible to the initial regimen. Active empirical antimicrobial coverage administered before admission to the intensive care unit is strongly associated with improved survival. Broad-spectrum antimicrobial agents are therefore recommended and should be instituted rapidly, preferably within the first hours after presentation. Risk factors for fungal infection should be assessed, as the incidence of fungal septic shock is increasing. Biomarkers such as C-reactive protein and procalcitonin have not proved reliable diagnostically but, when measured over time, can facilitate appropriate de-escalation of therapy and predict outcome. Glucocorticoids are often considered for patients with severe sepsis who do not respond to fluid resuscitation and vasopressor therapy. However, conclusive evidence for the efficacy of glucocorticoids in this setting is lacking.
Overwhelming Infection in Asplenic Patients
Patients without splenic function are at risk for overwhelming bacterial sepsis (See also Chap. 297). Asplenic adult patients succumb to sepsis at 58 times the rate of the general population. Most infections are thought to occur within the first l or 2 years, but the increased risk persists throughout life. The median interval between splenectomy and sepsis is 5.75 years, with a range of 1–19 years. In asplenia, encapsulated bacteria cause the majority of infections. Adults, who are more likely to have antibody to these organisms, are at lower risk than children. Streptococcus pneumoniae is the most common isolate, causing 40–70% of cases. The risk of infection with Haemophilus influenzae or Neisseria meningitidis is also greater in patients without splenic function, but reported cases are declining. Severe clinical manifestations of infections due to E. coli, S. aureus, group B streptococci, P. aeruginosa, Bordetella holmesii, and Capnocytophaga, Babesia, and Plasmodium species have been described.
A history of recent travel to endemic areas raises the possibility of infection with Babesia (See also Chap. 220). Between 1 and 4 weeks after a tick bite, the patient experiences chills, fatigue, anorexia, myalgia, arthralgia, shortness of breath, nausea, and headache; ecchymosis and/or petechiae are occasionally seen. The tick that most commonly transmits Babesia, Ixodes scapularis, also transmits Borrelia burgdorferi (the agent of Lyme disease) and Anaplasma; co-infection can occur, resulting in more severe disease. Infection with the European species Babesia divergens is more frequently fulminant than that due to the U.S. species Babesia microti. B. divergens causes a febrile syndrome with hemolysis, jaundice, hemoglobinemia, and renal failure and is associated with a mortality rate of >40%. Severe babesiosis is especially common in asplenic hosts but does occur in hosts with normal splenic function, particularly those >60 years of age and those with underlying immunosuppressive conditions such as HIV infection or malignancy. Complications include renal failure, acute respiratory failure, and DIC.
Tularemia (Chap. 165) is seen throughout the United States, but most cases recorded in 2015 occurred in South Dakota, Nebraska, Colorado, and Wyoming. This disease is associated with wild rabbit, tick, and tabanid fly contact. It can be transmitted by arthropod bite, handling of infected animal carcasses, consumption of contaminated food and water, or inhalation. The typhoidal form can be associated with gram-negative septic shock and a mortality rate of >30%, especially in patients with underlying comorbid or immunosuppressive conditions. Plague occurs infrequently in the United States (Chap. 166), primarily after contact with ground squirrels, prairie dogs, or chipmunks, but is endemic in other parts of the world, with >90% of all cases occurring in Africa. The septic form is particularly rare and is associated with shock, multiorgan failure, and a 30% mortality rate. These infections should be considered in the appropriate epidemiologic setting. The Centers for Disease Control and Prevention lists Francisella tularensis and Yersinia pestis (the agents of tularemia and plague, respectively) along with Bacillus anthracis (the agent of anthrax) as important organisms that might be used for bioterrorism (Chap. S2).
SEPSIS WITH SKIN MANIFESTATIONS
Maculopapular rashes may reflect early meningococcal or rickettsial disease but are usually associated with nonemergent infections (See also Chap. 16). Exanthems are usually viral. Primary HIV infection commonly presents with a rash that is typically maculopapular and involves the upper part of the body but can spread to the palms and soles. The patient is usually febrile and can have lymphadenopathy, severe headache, dysphagia, diarrhea, myalgias, and arthralgias. Recognition of this syndrome provides an opportunity to prevent transmission and to institute treatment and monitoring early on.
Petechial rashes caused by viruses are seldom associated with hypotension or a toxic appearance, although there can be exceptions (e.g., severe measles or arboviral infection). Petechial rashes limited to the distribution of the superior vena cava are rarely associated with severe disease. In other settings, petechial rashes require more urgent attention.
Almost three-quarters of patients with N. meningitidis bacteremia have a rash (See also Chap. 150). Meningococcemia most often affects young children (i.e., those 6 months to 5 years old). In sub-Saharan Africa, the high prevalence of serogroup A meningococcal disease has been a threat to public health for more than a century. Thousands of deaths occur annually in this area, which is known as the “meningitis belt,” and large epidemic waves occur approximately every 8–12 years. Serogroups W135 and X are also important emerging pathogens in Africa. In the United States, sporadic cases and outbreaks occur in day-care centers, schools (grade school through college, particularly among college freshmen living in residential halls), and army barracks. Household contacts of index cases are at 400–800 times greater risk of disease than the general population. Patients may have fever, headache, nausea, vomiting, myalgias, changes in mental status, and meningismus. However, the rapidly progressive form of disease is not usually associated with meningitis. The rash is initially pink, blanching, and maculopapular, appearing on the trunk and extremities, but then becomes hemorrhagic, forming petechiae. Petechiae are first seen at the ankles, wrists, axillae, mucosal surfaces, and palpebral and bulbar conjunctiva, with subsequent spread on the lower extremities and to the trunk. A cluster of petechiae may be seen at pressure points—e.g., where a blood pressure cuff has been inflated. In rapidly progressive meningococcemia (10–20% of cases), the petechial rash quickly becomes purpuric (see Fig. A1-41), and patients develop DIC, multiorgan failure, and shock; 50–60% of these patients die, and survivors often require extensive debridement or amputation of gangrenous extremities. Hypotension with petechiae for <12 h is associated with significant mortality. Cyanosis, coma, oliguria, metabolic acidosis, and elevated partial thromboplastin time also are associated with a fatal outcome. Antibiotics given in the office by the primary care provider before hospital evaluation and admission may improve prognosis; this observation suggests that early initiation of treatment may be life-saving. Meningococcal conjugate vaccines are protective against serogroups A, C, Y and W135 and are recommended for children 11–18 years of age and for other high-risk patients. Vaccines active against serogroup B are available and are recommended for high-risk individuals >10 years of age.
Rocky Mountain Spotted Fever and Other Rickettsial Diseases
RMSF is a tickborne disease caused by Rickettsia rickettsii that occurs throughout North and South America (See also Chap. 182). Other rickettsiae (e.g., R. parkeri, R. akari) can also cause spotted fever. Up to 40% of patients do not report a history of a tick bite, but a history of travel or outdoor activity (e.g., camping in tick-infested areas) can often be ascertained. For the first 3 days, headache, fever, malaise, myalgias, nausea, vomiting, and anorexia are documented. By day 3, half of patients have skin findings. Blanching macules develop initially on the wrists and ankles and then spread over the legs and trunk. The lesions become hemorrhagic and are frequently petechial. The rash spreads to palms and soles later in the course. The centripetal spread is a classic feature of RMSF but occurs in a minority of patients. Moreover, 10–15% of patients with RMSF never develop a rash. The patient can be hypotensive and develop noncardiogenic pulmonary edema, confusion, lethargy, and encephalitis progressing to coma. The CSF contains 10–100 cells/μL, usually with a predominance of mononuclear cells. The CSF glucose level is often normal; the protein concentration may be slightly elevated. Renal and hepatic injury as well as bleeding secondary to vascular damage are noted. For untreated infections, mortality rates are 20–30%. Delayed recognition and treatment are associated with a greater risk of death; Native Americans, children 5–9 years of age, adults >70 years old, and persons with underlying immunosuppression are at a 3- to 5-fold increased risk of death.
Other rickettsial diseases cause significant morbidity and mortality worldwide. Mediterranean spotted fever caused by Rickettsia conorii is found in Africa, southwestern and south-central Asia, and southern Europe. Patients have fever, flu-like symptoms, and an inoculation eschar at the site of the tick bite. A maculopapular rash develops within 1–7 days, involving the palms and soles but sparing the face. Elderly patients or those with diabetes, alcoholism, uremia, or congestive heart failure are at risk for severe disease characterized by neurologic involvement, respiratory distress, and gangrene of the digits or purpura fulminans. Mortality rates associated with this severe form of disease approach 50%. Epidemic typhus, caused by Rickettsia prowazekii, is transmitted in louse-infested environments and emerges in conditions of extreme poverty, war, and natural disaster. Patients experience a sudden onset of high fevers, severe headache, cough, myalgias, and abdominal pain. A maculopapular rash develops (primarily on the trunk) in more than half of patients and can progress to petechiae and purpura. Serious signs include delirium, coma, seizures, noncardiogenic pulmonary edema, skin necrosis, and peripheral gangrene. Mortality rates approached 60% in the preantibiotic era and continue to exceed 10–15% in contemporary outbreaks. Scrub typhus, caused by Orientia tsutsugamushi (a separate genus in the family Rickettsiaceae), is transmitted by larval mites or chiggers and is one of the most common infections in southeastern Asia and the western Pacific. The organism is found in areas of heavy scrub vegetation (e.g., along riverbanks). Patients may have an inoculation eschar and may develop a maculopapular rash, lymphadenopathy, and dyspnea. Severe cases progress to pneumonia, meningoencephalitis, myocarditis, DIC, and renal failure. Mortality rates range from 1% to 70% and vary by location, increasing age, myocarditis, delirium, pneumonitis, or signs of hemorrhage.
If recognized in a timely fashion, rickettsial disease is very responsive to treatment. Doxycycline (100 mg twice daily for 3–14 days) is the treatment of choice for both adults and children. The newer macrolides may be a suitable alternative, but mortality rates are higher when tetracycline-based treatment is not given.
Purpura fulminans is the cutaneous manifestation of DIC and presents as large ecchymotic areas and hemorrhagic bullae (See also Chaps. 150 and 297). Progression of petechiae to purpura, ecchymoses, and gangrene is associated with congestive heart failure, septic shock, acute renal failure, acidosis, hypoxia, hypotension, and death. Purpura fulminans has been associated primarily with N. meningitidis but, in splenectomized patients, may be associated with S. pneumoniae, H. influenzae, and S. aureus.
Septic shock caused by P. aeruginosa or Aeromonas hydrophila can be associated with ecthyma gangrenosum (see Figs. 159-1 and A1-34): hemorrhagic vesicles surrounded by a rim of erythema with central necrosis and ulceration. These gram-negative bacteremias are most common among patients with neutropenia, extensive burns, and hypogammaglobulinemia.
Other Infections Associated with Rash
Vibrio vulnificus and other noncholera Vibrio bacteremic infections (Chap. 163) can cause focal skin lesions and overwhelming sepsis in hosts with chronic liver disease, heavy alcohol consumption, iron storage disorders, diabetes, renal insufficiency, hematologic disease, or malignancy or other immunocompromising conditions. After ingestion of contaminated raw shellfish (typically oysters from the Gulf Coast in U.S. cases), there is a sudden onset of malaise, chills, fever, and hypotension. The patient develops bullous or hemorrhagic skin lesions, usually on the lower extremities, and 75% of patients have leg pain. The mortality rate can be as high as 50–60%, particularly when the patient presents with hypotension. Outcomes are improved when patients are treated with fluoroquinolones with or without cephalosporins or with tetracycline-containing regimens. Other infections, caused by agents such as Aeromonas, Klebsiella, and E. coli, can cause hemorrhagic bullae and death due to overwhelming sepsis in cirrhotic patients. Capnocytophaga canimorsus can cause septic shock in asplenic patients. Infection typically follows a dog bite. Patients present with fever, chills, myalgia, vomiting, diarrhea, dyspnea, confusion, and headache. Findings can include an exanthem or erythema multiforme (see Figs. 52-9 and A1-24), cyanotic mottling or peripheral cyanosis, petechiae, and ecchymosis. About 30% of patients with this fulminant form die of overwhelming sepsis and DIC, and survivors may require amputation because of gangrene.
TSS (Chaps. 142 and 143) is usually associated with erythroderma. The patient presents with fever, malaise, myalgias, nausea, vomiting, diarrhea, and confusion. There is a sunburn-type rash that may be subtle and patchy but is usually diffuse and is found on the face, trunk, and extremities. Erythroderma, which desquamates after 1–2 weeks, is more common in Staphylococcus-associated than in Streptococcus-associated TSS. Hypotension develops rapidly—often within hours—after the onset of symptoms. Multiorgan failure occurs. Early renal failure may precede hypotension and distinguishes this syndrome from other septic shock syndromes. There may be no indication of a primary focal infection, although possible cutaneous or mucosal portals of entry for the organism can be ascertained when a careful history is taken. Colonization rather than overt infection of the vagina or a postoperative wound, for example, is typical with staphylococcal TSS, and the mucosal areas appear hyperemic but not infected. Streptococcal TSS is more often associated with skin or soft tissue infection (including necrotizing fasciitis), and patients are more likely to be bacteremic. TSS caused by Clostridium sordellii is associated with childbirth or with skin injection of black-tar heroin. The diagnosis of TSS is defined by the clinical criteria of fever, rash, hypotension, and multiorgan involvement. (Of note, fever is typically absent when TSS is caused by C. sordellii.) The mortality rate is 5% for menstruation-associated TSS, 10–15% for nonmenstrual TSS, 30–70% for streptococcal TSS, and up to 90% for obstetric C. sordellii TSS. Clindamycin improves outcomes when included in the treatment regimen. Some studies have shown that use of IV immunoglobulin is associated with improved survival as well.
Viral hemorrhagic fevers (Chaps. 204 and 205) are zoonotic illnesses caused by viruses that reside in either animal reservoirs or arthropod vectors. These diseases occur worldwide and are restricted to areas where the host species live. They are caused by four major groups of viruses: Arenaviridae (e.g., Lassa fever in Africa), Bunyaviridae (e.g., Rift Valley fever in Africa; hantavirus hemorrhagic fever with renal syndrome in Asia; and Crimean-Congo hemorrhagic fever, which has an extensive geographic distribution), Filoviridae (e.g., Ebola and Marburg virus infections in Africa), and Flaviviridae (e.g., yellow fever in Africa and South America and dengue in Asia, Africa, and the Americas). Lassa fever and Ebola and Marburg virus infections are also transmitted from person to person. The vectors for most viral fevers are found in rural areas; dengue and yellow fever are important exceptions. After a prodrome of fever, myalgias, and malaise, patients develop evidence of vascular damage, petechiae, and local hemorrhage. Shock, multifocal hemorrhaging, and neurologic signs (e.g., seizures or coma) predict a poor prognosis. Dengue (Chap. 204) is the most common arboviral disease worldwide. More than half a million cases of dengue hemorrhagic fever occur each year, with at least 12,000 deaths. Patients have a triad of symptoms: hemorrhagic manifestations, evidence of plasma leakage, and platelet counts of <100,000/μL. Mortality rates are 10–20%. If dengue shock syndrome develops, mortality rates can reach 40%. Ebola infection has been associated with outbreaks with high mortality rates. The 2014 outbreak in West Africa had a mortality rate of >50%. Symptoms can appear 2–21 days after exposure, but most patients become ill within 9 days. The patient first presents with fatigue, fever, headache, and muscle pains, and the illness can progress to multiorgan failure and hemorrhaging. Careful volume-replacement therapy to maintain blood pressure and intravascular volume is key to survival in these infections. Ribavirin also may be useful against Arenaviridae and Bunyaviridae.
Other viral illnesses with rash, such as measles, can be associated with significant mortality rates. Steroids may sometimes be useful in severe disease in malnourished populations, especially if neurologic complications are present.
SEPSIS WITH A SOFT TISSUE/MUSCLE PRIMARY FOCUS
This infection is characterized by extensive necrosis of the subcutaneous tissue and fascia. It may arise at a site of minimal trauma or surgical incision and may also be associated with recent varicella, childbirth, or muscle strain. The most common causes of necrotizing fasciitis are group A streptococci alone (Chap. 143) and a mixed facultative and anaerobic flora (Chap. 124); the incidence of group A streptococcal necrotizing fasciitis has been increasing for the past quarter-century. Diabetes mellitus, IV drug use, chronic liver or renal disease, and malignancy are associated risk factors. Physical findings are initially minimal compared with the severity of pain and the degree of fever. The examination is often unremarkable except for soft tissue edema and erythema. The infected area is red, hot, shiny, swollen, and exquisitely tender. In untreated infection, the overlying skin develops blue-gray patches after 36 h, and cutaneous bullae and necrosis develop after 3–5 days. Necrotizing fasciitis due to a mixed flora, but not that due to group A streptococci, can be associated with gas production. Without treatment, pain decreases because of thrombosis of the small blood vessels and destruction of the peripheral nerves—an ominous sign. The mortality rate is 15–34% overall, >70% in association with TSS, and nearly 100% without surgical intervention. Necrotizing fasciitis may also be due to Clostridium perfringens (Chap. 149); in this condition, the patient is extremely toxic and the mortality rate is high. Within 48 h, rapid tissue invasion and systemic toxicity associated with hemolysis and death ensue. The distinction between this entity and clostridial myonecrosis is made by muscle biopsy. Necrotizing fasciitis caused by community-acquired MRSA also has been reported.
Myonecrosis is often associated with trauma or surgery but can develop spontaneously (See also Chap. 149). The incubation period is usually 12–24 h long, and massive necrotizing gangrene develops within hours of onset. Systemic toxicity, shock, and death can occur within 12 h. The patient’s pain and toxic appearance are out of proportion to physical findings. On examination, the patient is febrile, apathetic, tachycardic, and tachypneic and may express a feeling of impending doom. Hypotension and renal failure develop later, and hyperalertness is evident preterminally. The skin over the affected area is bronze-brown, mottled, and edematous. Bullous lesions with serosanguineous drainage and a mousy or sweet odor can develop. Crepitus can occur secondary to gas production in muscle tissue. The mortality rate is >65% for spontaneous myonecrosis, which is often associated with Clostridium septicum or C. tertium and underlying malignancy. The mortality rates associated with trunk and limb infection are 63% and 12%, respectively, and any delay in surgical treatment increases the risk of death.
NEUROLOGIC INFECTIONS WITH OR WITHOUT SEPTIC SHOCK
Bacterial meningitis is one of the most common infectious disease emergencies involving the central nervous system (See also Chap. 133). Although hosts with cell-mediated immune deficiency (including transplant recipients, diabetic patients, elderly patients, and cancer patients receiving certain chemotherapeutic agents) are at particular risk for Listeria monocytogenes meningitis, most cases in adults are due to S. pneumoniae (30–60%) and N. meningitidis (10–35%). The classic presentation of fever, meningismus, and altered mental status is seen in only one-half to two-thirds of patients. The elderly can present without fever or meningeal signs. Cerebral dysfunction is evidenced by confusion, delirium, and lethargy that can progress to coma. In some cases, the presentation is fulminant, with sepsis and brain edema; papilledema at presentation is unusual and suggests another diagnosis (e.g., an intracranial lesion). Focal signs, including cranial nerve palsies (IV, VI, VII), can be seen in 10–20% of cases; 50–70% of patients have bacteremia. A poor outcome is associated with coma, seizures, hypotension, a pneumococcal etiology, respiratory distress, a CSF glucose level of <0.6 mmol/L (<10 mg/dL), a CSF protein level of >2.5 g/L, a peripheral white blood cell count of <5000/μL, and a serum sodium level of <135 mmol/L. Rapid initiation of treatment is essential; the odds of an unfavorable outcome may increase by 30% for each hour that treatment is delayed. Dexamethasone is an adjunctive treatment for meningitis in adults, especially for infections caused by S. pneumoniae. It must be given before or with the first dose of antibiotics; otherwise, it is unlikely to improve outcomes.
Suppurative Intracranial Infections
In suppurative intracranial infections, rare intracranial lesions present along with sepsis and hemodynamic instability (See also Chap. 135). Rapid recognition of the toxic patient with central neurologic signs is crucial to improvement of the dismal prognosis of these entities. Patients with diabetes or hematologic disease may be at increased risk for these infections. Subdural empyema arises from the paranasal sinus in 60–70% of cases. Microaerophilic streptococci and staphylococci are the predominant etiologic organisms. The patient is toxic, with fever, headache, and nuchal rigidity. Of all patients, 75% have focal signs and 6–20% die. Despite improved survival rates, 15–44% of patients are left with permanent neurologic deficits. Septic cavernous sinus thrombosis follows a facial or sphenoid sinus infection; 70% of cases are due to staphylococci (including MRSA), and the remainder are due primarily to aerobic or anaerobic streptococci. Fungi have been common in some series. A unilateral or retro-orbital headache progresses to a toxic appearance and fever within days. Three-quarters of patients have unilateral periorbital edema that becomes bilateral and then progresses to ptosis, proptosis, ophthalmoplegia, and papilledema. The mortality rate is as high as 30%. Septic thrombosis of the superior sagittal sinus spreads from the ethmoid or maxillary sinuses and is caused by S. pneumoniae, other streptococci, and staphylococci. The fulminant course is characterized by headache, nausea, vomiting, rapid progression to confusion and coma, nuchal rigidity, and brainstem signs. If the sinus is totally thrombosed, the mortality rate exceeds 80%. Broad-spectrum antibiotics and early surgical intervention at the primary site of infection may improve outcomes. Anticoagulation or steroids are of uncertain benefit.
Brain abscess often occurs without systemic signs (See also Chap. 135). Almost half of patients are afebrile, and presentations are more consistent with a space-occupying lesion in the brain; 70% of patients have headache and/or altered mental status, 50% have focal neurologic signs, and 25% have papilledema. Abscesses can present as single or multiple lesions resulting from contiguous foci or hematogenous infection, such as endocarditis, or after surgery or trauma. The infection progresses over several days from cerebritis to an abscess with a mature capsule. More than half of infections are polymicrobial, with an etiology consisting of aerobic bacteria (primarily streptococcal species) and anaerobes. Abscesses arising hematogenously are especially apt to rupture into the ventricular space, causing a sudden and severe deterioration in clinical status and a high mortality rate. Otherwise, mortality is low (<20%) but morbidity is high (30–55%). Patients presenting with stroke and a parameningeal infectious focus, such as sinusitis or otitis, may have a brain abscess, and physicians must maintain a high level of suspicion. Prognosis worsens in patients with a fulminant course, delayed diagnosis, abscess rupture into the ventricles, multiple abscesses, or abnormal neurologic status at presentation. In one study, mortality at 1 year was 19%.
This entity should be urgently considered if patients who have recently traveled to areas endemic for malaria present with a febrile illness and lethargy or other neurologic signs (See also Chap. 219). Fulminant malaria is caused by Plasmodium falciparum and is associated with temperatures of >40°C (>104°F), hypotension, jaundice, acute respiratory distress syndrome, and bleeding. By definition, any patient with a change in mental status or repeated seizure in the setting of fulminant malaria has cerebral malaria. In adults, this nonspecific febrile illness progresses to coma over several days; occasionally, coma occurs within hours and death within 24 h. Nuchal rigidity and photophobia are rare. On physical examination, symmetric encephalopathy is typical, and upper motor neuron dysfunction with decorticate and decerebrate posturing can be seen in advanced disease. Unrecognized infection results in a 20–30% mortality rate.
Intracranial and Spinal Epidural Abscesses
Spinal and intracranial epidural abscesses (SEAs and ICEAs) can result in permanent neurologic deficits, sepsis, and death (See also Chap. 434). At-risk patients include those with diabetes mellitus; IV drug use; chronic alcohol abuse; recent spinal trauma, surgery, or epidural anesthesia; and other comorbid conditions, such as HIV infection. Fungal epidural abscess and meningitis can follow epidural or paraspinal glucocorticoid injections. In the United States and Canada, where early treatment of otitis and sinusitis is typical, ICEA is rare but the number of cases of SEA is on the rise. In Africa and areas with limited access to health care, SEAs and ICEAs cause significant morbidity and mortality. ICEAs typically present as fever, mental status changes, and neck pain, while SEAs often present as fever, localized spinal tenderness, and back pain. ICEAs are typically polymicrobial, whereas SEAs are most often due to hematogenous seeding, with staphylococci the most common etiologic agent. Early diagnosis and treatment, which may include surgical drainage, minimize rates of mortality and permanent neurologic sequelae. Outcomes are worse for SEA due to MRSA, for infection at a higher vertebral-body level, for impaired neurologic status on presentation, and for dorsal rather than ventral location of the abscess. Elderly patients and persons with renal failure, malignancy, and other comorbidities also have less favorable outcomes.
OTHER FOCAL SYNDROMES WITH A FULMINANT COURSE
Infection at virtually any primary focus (e.g., osteomyelitis, pneumonia, pyelonephritis, or cholangitis) can result in bacteremia and sepsis. Lemierre’s syndrome—jugular septic thrombophlebitis caused by Fusobacterium necrophorum—is associated with metastatic infectious emboli (primarily to the lung but sometimes to the liver or other organs) and sepsis, with mortality rates of >15%. TSS has been associated with focal infections such as septic arthritis, peritonitis, sinusitis, and wound infection. Rapid clinical deterioration and death can be associated with destruction of the primary site of infection, as is seen in endocarditis and in infections of the oropharynx (e.g., Ludwig’s angina or epiglottitis, in which edema suddenly compromises the airway).
Individuals with diabetes or immunocompromising conditions such as solid organ transplants or hematologic malignancies are at risk for invasive rhinocerebral mucormycosis (See also Chap. 213). Patients present with low-grade fever, dull sinus pain, diplopia, decreased mental status, decreased ocular motion, chemosis, proptosis, dusky or necrotic nasal turbinates, and necrotic hard-palate lesions that respect the midline. Without rapid recognition and intervention, the process continues on an inexorable invasive course, with mortality rates of 50–85% or greater. Uncontrolled diabetes and increasing age are negative prognostic factors.
Acute Bacterial Endocarditis
This entity presents with a much more aggressive course than subacute endocarditis (See also Chap. 123). Bacteria such as S. aureus, S. pneumoniae, L. monocytogenes, Haemophilus species, and streptococci of groups A, B, and G attack native valves. Native-valve endocarditis caused by S. aureus (including MRSA strains) is increasing, particularly in health care settings. Mortality rates range from 10% to 40%. The host may have comorbid conditions such as underlying malignancy, diabetes mellitus, IV drug use, or alcoholism. The patient presents with fever, fatigue, and malaise <2 weeks after onset of infection. On physical examination, a changing murmur and congestive heart failure may be noted. Hemorrhagic macules on palms or soles (Janeway lesions) sometimes develop. Petechiae, Roth’s spots, splinter hemorrhages, and splenomegaly are unusual. Rapid valvular destruction, particularly of the aortic valve, results in pulmonary edema and hypotension. Myocardial abscesses can form, eroding through the septum or into the conduction system and causing life-threatening arrhythmias or high-degree conduction block. Large friable vegetations can result in major arterial emboli, metastatic infection, or tissue infarction. Older patients with S. aureus endocarditis are especially likely to present with nonspecific symptoms—a circumstance that delays diagnosis and worsens prognosis. Rapid intervention is crucial for a successful outcome.
Inhalational anthrax, the most severe form of disease caused by B. anthracis, had not been reported in the United States for more than 25 years until the use of this organism as an agent of bioterrorism in 2001 (See also Chap. S2). Patients presented with malaise, fever, cough, nausea, drenching sweats, shortness of breath, and headache. Rhinorrhea was unusual. All patients had abnormal chest roentgenograms at presentation. Pulmonary infiltrates, mediastinal widening, and pleural effusions were the most common findings. Hemorrhagic meningitis was documented in 38% of these patients. Survival was more likely when antibiotics were given during the prodromal period and when multidrug regimens were used. In the absence of urgent intervention with antimicrobial agents and supportive care, inhalational anthrax progresses rapidly to hypotension, cyanosis, and death.
Viral Respiratory Tract Illness
Viral respiratory tract illnesses can cause severe disease; several new syndromes have been described in the past decade. For patients who present with a respiratory illness and a relevant exposure and travel history, these viral illnesses must be considered and appropriate infection control measures instituted in addition to supportive care.
Avian and Swine Influenza
Human cases of avian influenza have occurred primarily in Southeast Asia, particularly Vietnam (H5N1) and China (H7N9) (See also Chap. 195). Avian influenza should be considered in patients with severe respiratory tract illness, particularly if they have been exposed to poultry. Patients present with high fever, an influenza-like illness, and lower respiratory tract symptoms; this illness can progress rapidly to bilateral pneumonia, acute respiratory distress syndrome, multiorgan failure, and death. Younger age appears to be associated with a lower risk of complications. Early antiviral treatment with neuraminidase inhibitors should be initiated along with aggressive supportive measures. Unlike avian influenza, whose human-to-human transmission has so far been rare and has not been sustained, influenza caused by a novel swine-associated A/H1N1 virus has spread rapidly throughout the world; by 2012, 214 countries had diagnosed cases of influenza A/H1N1, with 18,449 deaths. Patients most at risk of severe disease are children <5 years of age, elderly persons, patients with underlying chronic conditions, and pregnant women. Obesity also has been identified as a risk factor for severe illness. Immunosuppression and co-infection with S. aureus at presentation are independent risk factors for increased mortality.
Severe acute respiratory syndrome (SARS) was identified in 2002 in China but has been diagnosed in several countries, primarily in Asia. Possible animal reservoirs include bats and civets. SARS is caused by a coronavirus and is characterized by efficient human transmission but relatively low mortality. It spreads from person to person via droplets; “super-spreader” airborne events have occurred. The potential pandemic with SARS was controlled through identification and isolation of infected patients. A 3- to 7-day prodrome characterized by fever, malaise, headache, and myalgia can progress to nonproductive cough, dyspnea, and respiratory failure. The risk of contagion is low during the prodrome. Older patients and those with diabetes mellitus, chronic hepatitis B, and other comorbidities can have less favorable outcomes.
Middle East respiratory syndrome (MERS) is caused by a novel betacoronavirus and was first recognized in 2012 in Saudi Arabia. Human cases have been associated with direct and indirect contact with dromedary camels. Unlike SARS, MERS exhibits inefficient human transmission but carries a high mortality rate. As of 2015, 1180 cases had been confirmed, with 40% mortality. MERS ranges from asymptomatic infection to acute respiratory distress syndrome, multiorgan failure, and death. Elderly men with comorbidities appear to be at highest risk for poor outcomes. Despite little documented human-to-human transmission in the community, nosocomial infection must be prevented by adherence to strict infection control practices. MERS is currently a low-level public health threat and is likely to remain so unless the virus mutates and its transmissibility increases.
Hantavirus Pulmonary Syndrome
Hantavirus pulmonary syndrome has been documented in the United States since 1993 (primarily the southwestern states, west of the Mississippi River), Canada, and South America (See also Chap. 204). Most cases occur in rural areas and are associated with exposure to rodents. Patients present with a nonspecific viral prodrome of fever, malaise, myalgias, nausea, vomiting, and dizziness that may progress to pulmonary edema, respiratory failure, and death. Hantavirus pulmonary syndrome causes myocardial depression and increased pulmonary vascular permeability; therefore, careful fluid resuscitation and use of pressor agents are crucial. Aggressive cardiopulmonary support during the first few hours of illness can be life-saving in this high-mortality syndrome. The early onset of thrombocytopenia may help distinguish this syndrome from other febrile illnesses in an appropriate epidemiologic setting.
Clostridium difficile Infection
C. difficile infection (CDI) is a toxin-mediated diarrheal syndrome that is strongly associated with prior antibiotic use. Proton-pump inhibitors have also been identified as a potential risk factor for the disease. Although most cases of CDI have occurred in the health care setting, community-onset CDI is increasing. Overall, community-onset cases occur in younger patients than nosocomial cases. Patients with community-onset CDI are less likely to have a history of antibiotic or protein-pump inhibitor use. CDI is associated with significant morbidity and mortality, particularly among older patients. The Centers for Disease Control and Prevention has reported that C. difficile infection is one of the top three health threats associated with antibiotic use.
Acutely ill febrile patients with the syndromes discussed in this chapter require close observation, aggressive supportive measures, and—in most cases—admission to intensive care units. The most important task of the physician is to distinguish these patients from other infected febrile patients whose illness will not progress to fulminant disease. The alert physician must recognize the acute infectious disease emergency and then proceed with appropriate urgency.
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Additional Online References
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