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INTRODUCTION

GUIDING QUESTIONS

  1. Who is likely to become ill with one of these serious adult viral illnesses?

  2. What are the presenting features and laboratory tests that are useful in making a diagnosis?

  3. What are the major complications of each of these diseases?

  4. What are the treatments available for each viral illness?

  5. Which patients should be treated?

  6. What are the preventive measures that are available?

  7. How does the avian influenza virus differ from other influenza viruses, and why should we worry?

VARICELLA IN THE ADULT

Varicella virus [also called varicella–zoster virus (VZV)] is a double-stranded DNA herpesvirus that causes two diseases: varicella (chickenpox) and zoster (shingles). Chickenpox is a manifestation of primary infection; zoster is caused by reactivation of latent infection.

Epidemiology

The epidemiology of VZV infection has been drastically altered by the introduction of universal vaccination against chickenpox. Approximately 4 million cases of chickenpox and 500,000 cases of zoster and 100–150 deaths attributable to VZV infection occurred each year in the United States before the introduction of the single-dose VZV vaccine in 1995. By 2005, dramatic reductions in chickenpox occurred, with the incidence declining by approximately 85%. Two-dose vaccination was instituted in 2006. By 2007, there were only 14 deaths attributed to varicella. Of these only 1 was in a child and 11 were in elderly patients.

Chickenpox is primarily a disease of childhood. Nevertheless, 10% of the adult population is estimated to be at risk of infection, and the majority of cases in the United States now occur in adults. The virus circulates exclusively in humans, and no other reservoirs of infection are known. The disease becomes epidemic in the susceptible population in winter and early spring, affecting both sexes and all races equally. Transmission occurs via the respiratory route and requires close contact even though the virus is highly infectious, with attack rates of 70–90% in susceptible family members.

In contrast, zoster affects primarily elderly people. Zoster is caused by reactivation of latent VZV in people who previously had chickenpox. Zoster occurs in up to 1% of people over 60 years of age, and 75% of cases occur in those over the age of 45 years. The development of zoster is not associated with exposure to other people with chickenpox or zoster, although patients with zoster may themselves be capable of transmitting the virus to susceptible individuals. Zoster occasionally occurs in younger individuals, particularly those who are immunosuppressed.

CASE 14-1

A 36-year-old mother of two presented to the emergency room with complaints of shortness of breath. She had noted the onset of the skin lesions and low-grade fever 2 days before admission. Her son was recovering from a recent bout of chickenpox. Aside from the rash, she had been feeling well until the day of admission, when she began experiencing a dry cough and increasing shortness of breath....

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