Confirming an Outbreak
Confirming the existence of an epidemic is not always straightforward. In part, that is because clear definitions of outbreak thresholds do not exist for all diseases. For some diseases, a single case may indicate an outbreak. These include cholera, measles, yellow fever, shigella, and the viral hemorrhagic fevers.
General guidelines for meningococcal meningitis are that for populations >30,000, 15 cases/100,000 persons/week in 1 week indicates an outbreak. However, with a high outbreak risk (i.e., no outbreak for 3+ years and vaccination coverage <80%), this threshold is reduced to 10 cases/100,000 persons/week. In populations <30,000, an incidence of 5 cases in 1 week or a doubling of cases over a 3-week period confirms an outbreak.
For malaria, an increase in the number of cases above what is expected for the time of year among a defined population in a defined area may indicate an outbreak.1
Post-Disaster Infectious Diseases
Following natural disasters, multiple factors increase the risk of contracting a communicable disease. These include inadequate sanitation, crowded conditions, food shortages, contaminated water, and inadequate immunization. Take all preventive measures possible and be alert for signs of potential epidemic diseases to avoid or quell a secondary disaster.
The diseases listed in Table 32-1 are common following disasters. All but tetanus have the potential of developing into epidemics. The best strategy is prevention, since adequate resources may not be available for treatment—or there may be no good treatment. Unfortunately, some preventive measures, such as hand washing, may not be easy to abide by in austere circumstances.
Table Graphic Jump Location Table 32-1 Infectious Diseases Frequently Seen Post-Disaster ||Download (.pdf)
Table 32-1 Infectious Diseases Frequently Seen Post-Disaster
|Disease||Transmission||Prevention/Control||Clinical Features||Incubation Period|
|Cholera||Fecal/oral, contaminated water or food||Hand washing, proper handling of water/food and sewage disposal||Profuse watery diarrhea, vomiting||2 hr to 5 days|
|Leptospirosis||Fecal/oral, contaminated water||Avoid entering contaminated water; safe water source||Sudden-onset fever, headache, chills, vomiting, severe myalgia||2-28 days|
|Hepatitis||Fecal/oral, contaminated water or food||Hand washing, proper handling of water/food and sewage disposal; hepatitis A vaccine||Jaundice, abdominal pain, nausea, diarrhea, fever, fatigue, loss of appetite||15-50 days|
|Bacillary dysentery||Fecal/oral, contaminated water or food||Hand washing, proper handling of water/food and sewage disposal||Malaise, fever, vomiting, blood and mucous in stool||12-96 hr|
|Typhoid fever||Fecal/oral, contaminated water or food||Hand washing, proper handling of water/food and sewage disposal; mass vaccination in some settings||Sustained fever, headache, constipation||3-14 days|
|Pneumonia||Person-to-person by airborne respiratory droplets||Isolation; proper nutrition. If cause is Streptococcus, give polyvalent vaccine to high-risk populations||Cough, dyspnea, tachypnea, retractions||1-3 days|
|Measles||Person-to-person by airborne respiratory droplets||Rapid mass vaccination within 72 hr of initial case report (priority to high-risk groups if limited supply); vitamin A in children 6 ...|