Clinical disease due to HAV resembles other types of acute hepatitis, and diagnosis is generally dependent on laboratory confirmation of infection by the virus. The incubation period is approximately 28 days but can vary from 15 to 50 days. Initial symptoms include pyrexia, malaise, anorexia, which is often quite prominent, nausea, vomiting, and abdominal discomfort or pain. These initial symptoms are followed a few days later by the development of jaundice with a typical yellow discoloration of the skin, especially the sclera of eye, and darkening of the urine. The acute phase usually lasts between 1 and 3 weeks and is followed by a varying period of convalescence characterized by fatigue, malaise, anorexia, and persisting nausea.
Complications are rare. Approximately 5% of patients develop cholestatic hepatitis with pruritis and steatorrhea. Fulminant hepatitis, characterized by precipitous loss of liver function rapidly leading to liver failure and death, occurs in approximately 0.01% of cases. Chronic disease and chronic excretion of virus does not occur. However, up to 10% of patients will relapse, that is, will suffer a recurrence within 1-4 months after acute disease, and these recurrences may persist for several months.
The severity of hepatitis A disease is directly dependent on a number of factors: age, underlying liver disease, immunosuppression, and pregnancy (13). Thus, jaundice occurs in less than 10% of children under 6 years of age, 40-50% of older children, and 70-80% of adults. The overall mortality in the United States is less than 0.1%, but mortality is somewhat higher in children less than 5 years of age (0.15%) and even higher in older persons over 50 years of age (2.7%). Similarly, increased mortality is seen in immunosuppression and in patients with underlying liver disease such as cirrhosis. In most older children and adults the disease is, at best, an uncomfortable to debilitating illness, which runs a course of 1-2 months. However, some 11-22% of cases are hospitalized (14), and studies of work absenteeism have shown that sick leave for hepatitis A can vary from 27 to 60 days (60 days was found at the Willowbrook State School to be the average duration of sick leave among staff working at the institution) at an estimated annual direct and indirect cost in the United States of over $300 million (15).
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