Viral Hepatitis Strategic Plan

Overview of Viral Hepatitis

Hepatitis A

Overview

Hepatitis A is caused by an infection with hepatitis A virus (HAV) . It is the most commonly acquired form of viral hepatitis in the United States and one of the most frequently reported vaccine-preventable diseases. Due to under-reporting of cases and asymptomatic or unrecognized infection, many more HAV infections occur than are reported each year in the United States. In 2001, 10,609 cases were reported, but after accounting for under-reporting, an estimated 45,000 acute clinical cases occurred. An estimated total of 93,000 new infections occurred, including asymptomatic infections. According to the NHANES III study, about one third (31.3%) of the U.S. population has serologic evidence of ever having had HAV infection.2

Historically the highest rates of HAV infection were reported among children, adolescents and young adults. Approximately one third of reported cases involved children less than 15 years of age. Since 1998, there has been a decline among all age groups due to wide spread use of the hepatitis A vaccine.

Hepatitis A does not result in a chronic infection, unlike hepatitis B and C. In addition, once someone has been infected with hepatitis A, they cannot be reinfected.

Clinical Features

The incubation period of hepatitis A ranges from 15-50 days with the average being 28-30 days. Individuals infected with HAV generally have an abrupt onset of fever, malaise, anorexia, nausea, abdominal discomfort, dark urine and jaundice.

Adults tend to have symptoms more often than children. The severity of disease increases with age. Jaundice occurs among less than 10% of children younger than six years of age, 40%-50% of older children, and 70%-80% of adults. Complications from HAV infection include fulminant hepatitis, cholestatic hepatitis and relapsing hepatitis.

Diagnosis

Most types of hepatitis present with similar symptomatology; therefore, serologic testing must be done to confirm a diagnosis of HAV infection. The HAV IgM antibody test is the most commonly used test to diagnose acute HAV infection. It is usually present 5-10 days before symptoms develop and remains present for approximately six months. HAV IgG antibody is an indication of past infection or of past vaccination. It is present early in the course of infection, remains detectable for the lifetime of the individual, and confers lifelong protection against infection. Individuals with acute hepatitis A often have elevated liver function tests.

Transmission

Hepatitis A is transmitted in several different ways. The most common mode of hepatitis A transmission is via the fecal-oral route, by putting something in the mouth that has been contaminated by feces of a person with hepatitis A, often through household or sexual contact. Close person-to-person contact is the most common mode of transmission. Hepatitis A may also be spread through contaminated food or water. Hepatitis A transmission can occur when an infected food handler directly handles uncooked or cooked foods. Transmission usually occurs because of lack of hand washing by the infected food handler. Outbreaks have also been reported in association with foods contaminated before wholesale distribution, such as fresh vegetables (onions) and shellfish (clams, oysters) contaminated at the time of harvesting or processing. HAV transmission can occur as a result of blood exposures such as injecting drug use or blood transfusion because viremia can occur prior to the onset of illness in infected persons. Hepatitis A is rarely transmitted through blood or blood products due to screening of blood products for HAV.

At-risk Groups

The following groups are at highest risk for contracting hepatitis A:

  • Household and sexual contacts of infected individuals,
  • Persons, especially children, living in regions of the U.S. with consistently elevated rates of hepatitis A,
  • Persons traveling to countries where hepatitis A is common such as Central and South America, Africa, Middle East, Asia, and the Western Pacific,
  • Men who have sex with men (MSM) , and
  • Injecting and non-injecting drug users.

According to CDC's National Notifiable Disease Surveillance System, from 1990 through 2000, the most frequently reported source of HAV infection was personal contact (household or sexual) with an infected person (14%). Two percent of cases involved a child or employee in day-care; 6% of cases were a contact of a child or employee in day-care; 5% of cases reported recent international travel; and 4% of cases reported being part of a recognized foodborne outbreak. Injection drug use was a reported risk factor in 6% of cases; men who have sex with men represented 10% of cases. Forty-five percent of reported hepatitis A cases could not identify a risk factor for their infection.

Treatment

There are no specific medicines or antibiotics that can be used to cure HAV infection once the symptoms appear. Persons acutely infected with HAV should avoid alcohol and other hepatotoxic medications until they have fully recovered.

Prevention

Hepatitis A vaccine is the best protection against HAV infection. Currently in the U. S. there are two inactivated vaccines licensed and available for those two years of age and older. Both vaccines are highly immunogenic. Approximately 94-100% of children, adolescents, and adults develop protective levels of antibody within one month after the first dose of vaccine; essentially 100% of healthy individuals vaccinated develop protective antibody after completing the two-dose series.3 There is limited data on the long-term persistence of antibody. Some models suggest protective antibody levels persist for at least 20 years. The vaccine is less immunogenic for certain groups, such as the elderly, immunocompromised persons, and transplant recipients.7

In 2001, the Food and drug Administration (FDA) approved a combination hepatitis A and B vaccine. This vaccine is administered in a three dose series and is approved for use in those 18 years or older.

Hepatitis A vaccination is recommended for the following groups: travelers to areas with increased rates of hepatitis A, men who have sex with men, injecting and non-injecting drug users, persons with clotting-factor disorders (e.g., hemophilia) , persons with chronic liver disease, and children living in areas with increased rates of hepatitis A.

Immune globulin (IG) provides protection against HAV to those already exposed (postexposure prophylaxis) . When administered within two weeks of an exposure, IG is greater than 85% effective in preventing HAV infection. Postexposure use of IG is routinely used for household or intimate contacts of persons with hepatitis A. It may also be used in outbreak situations occurring in institutional settings such as child day care centers and after common source exposures (e.g., persons who ate food prepared by an infected food handler). IG can also be used as pre-exposure prophylaxis for travelers to areas of high endemicity of hepatitis A, particularly if travel departure is less than 2-4 weeks away. IG is protective against HAV infection immediately after administration, whereas the hepatitis A vaccine can take 2-4 weeks for an immune response to develop.

Finally, washing hands with soap and water after using the bathroom, changing diapers, and before preparing and eating food helps prevent the spread of hepatitis A.