Chapter 206. Viral Infections

• Infectious Mononucleosis

  1. What are the major complications in Epstein–Barr virus–associated infectious mononucleosis (“mono”)?

  2. What other viruses cause a mononucleosis-type clinical syndrome?

  3. What are the appropriate diagnostic tests for acute Epstein–Barr virus infections?

  4. What are the current treatment recommendations for Epstein–Barr virus–associated infectious mononucleosis?

• Varicella-Zoster Virus

  1. What are the complications of adult varicella-zoster virus infection?

  2. What are the treatment options for varicella-zoster virus infections?

  3. What is the best way to treat postherpetic neuralgia?

  4. What are the indications for the varicella-zoster vaccine in adults?

• Influenza

  1. When should patients with influenza-like illness be hospitalized?

  2. How good are rapid virus diagnostic tests for influenza virus?

  3. How is influenza infection best treated with antiviral agents?

  4. What are the major complications of acute influenza?

Introduction

Viruses may infect any organ system of the body and present with common or rare clinical conditions. Viral infections may be trivial or life-threatening. Any given clinical syndrome, such as pneumonia, may have a multitude of viral causes. Additionally, some viruses, such as human cytomegalovirus (CMV), have protean clinical manifestations, including pneumonitis, colitis, encephalitis, and a mononucleosis-like syndrome. This chapter will discuss three common viruses in hospitalized patients: Epstein–Barr virus (EBV), varicella-zoster virus (VZV), and influenza virus, along with their complications.

Epidemiology

Infectious mononucleosis is spread by close physical contact with infected secretions, and is often referred to as “kissing disease.” It is most often seen in adolescents and young adults and is not serious in most individuals. However, it can lead to significant time away from school or work, and may be associated with persistent fatigue and prolonged convalescence in some individuals.

Pathophysiology

Although other viruses produce a similar clinical syndrome, infectious mononucleosis is most often caused by acute EBV infection. Most people become infected with EBV before the age of 6. When EBV infection occurs early in life, it is usually asymptomatic or subclinical. Infection in young adulthood is more likely to lead to clinical “mono,” perhaps because of a more robust immune response. The major cell infected by EBV is the B lymphocyte; up to 20% of host B lymphocytes may be infected. Cellular immunity is heavily involved in containing EBV infection; the atypical lymphocytes seen in acute EBV infections are activated CD8+ T cells. The humoral immune system produces antibodies directed against the virus. For unclear reasons, antibodies are also produced against unrelated antigens found on sheep and horse red cells. These antibodies are known as heterophile antibodies, and they form the basis for the mononucleosis spot (“monospot”) test.

Clinical Presentation

Infectious mononucleosis usually presents with exudative pharyngitis, fever, and symmetrically enlarged cervical lymph nodes. Sore throat may cause severe discomfort. Tonsillitis is common; if massive, “kissing tonsils” may impinge on the airway. Fever lasts from a few days to 2 weeks. The cervical lymphadenopathy can become generalized but usually subsides over ...