Hepatitis A
Hepatitis A
Disease History, Characteristics, and Transmission
Introduction
Hepatitis is an inflammation of the liver that can be caused by exposure to chemicals including alcohol, or by any one of six hepatitis viruses. Hepatitis A infection is caused by the Hepatitis A virus (HAV), and was formerly known as infectious hepatitis. HAV was discovered in the early 1970s in the stool of a patient incubating the disease. Hepatitis A is an acute disease, with symptoms including nausea, malaise, diarrhea and enlarged liver. Some infected people, particularly children, have no symptoms. Unlike other forms of hepatitis, it does not progress to chronic disease, which damages the liver.
Hepatitis A has been on the decline in developed countries since the 1970s, although epidemics still occur, especially under conditions of overcrowding and poor hygiene. It is still a risk to travelers, as HAV can be spread through seafood, fruit, and vegetables that have been in contact with contaminated water. Those at risk can be protected through vaccination against HAV.
Disease History, Characteristics, and Transmission
Hepatitis A is a single-stranded RNA virus (that is, its genetic material is made of RNA, not DNA), unrelated to the other hepatitis viruses. During its average incubation time of 28 days, it first infects the intestines and then passes through the blood into the liver. The onset of symptoms including nausea, loss of appetite, diarrhea and fever, is acute. The person with hepatitis A may have an enlarged liver with pain and tenderness in the upper right abdomen. Many go on to develop jaundice, a yellowing of the skin and eyes resulting from liver inflammation. The urine may be dark and stools a pale clay color.
The vast majority of cases of hepatitis A clear up within a week or so, although 15% are prolonged and relapsing over a period of months. The disease does not, however, become chronic like hepatitis B and hepatitis C. Only 0.3% of the cases reported to the Centers for Disease Control and Prevention (CDC) prove fatal, although the mortality rate rises to nearly two percent in those over 50 years of age. Hepatitis A is transmitted through the fecal-oral route, commonly through eating seafood, raw fruit, or vegetables that have come into contact with water contaminated with infected sewage.
Scope and Distribution
Adults are more likely than children to develop symptoms of hepatitis A. Household and sexual partners of those with hepatitis A are at elevated risk of contracting the disease, as are men who have sex with men, and both injecting and non-injecting drug users. Epidemic of hepatitis A are fairly common in institutions such as prisons and nursing homes, and among those of low socioeconomic status living in overcrowded conditions.
According to CDC data, there were 4,488 cases of acute hepatitis A in the USA in 2005. Computer modeling of this data suggests the true number of new infections that year was about 42,000 (many of which would have been asymptomatic). This represents the lowest figure since 2001, which is a reflection of the decline in hepatitis A in developed countries, although epidemics may still occur where hygiene is poor. Hepatitis A most often represents a risk to those traveling into less developed countries where the disease is common.
Treatment and Prevention
There is no definitive treatment for hepatitis A, and often the disease resolves with adequate nutrition and rest. Those at risk of infection can be given either immune serum globulin, prepared from pooled plasma, or a vaccine against hepatitis A (or both). There are two hepatitis A vaccines, both made of inactivated virus. One protects against hepatitis A only, while the other is a combined hepatitis A and hepatitis B vaccine.
Impacts and Issues
People travel more widely today than ever before which means they may be exposed to diseases they otherwise would not be. For travelers, Hepatitis A is the most common preventable infection. The extent of the risk depends upon the length of stay, the living conditions in the place visited, and the level of hepatitis A in the country visited. In general, the risk of contracting hepatitis A is low in North America (except Mexico), New Zealand, Australia and developed European countries. However, epidemics still occur even on standard tourist itineraries. Before traveling, it is advisable to check out the latest information on proposed destinations through public health departments and the Centers for Disease Control and Prevention.
WORDS TO KNOW
FECAL-ORAL ROUTE: The transmission of minute particles of fecal material from one organism (human or animal) to the mouth of another organism.
IMMUNE GLOBULIN: Globulins are a type of protein found in blood. The immunoglobulins (also called immune globulins) are Y-shaped globulins that act as antibodies, attaching themselves to invasive cells or materials in the body so that they can be identified and attacked by the immune system. There are five immune globulins, designated IgM, IgG, IgA, IgD, and IgE.
INACTIVATED VIRUS: Inactivated virus is incapable of causing disease but still stimulates the immune system to respond by forming antibodies.
JAUNDICE: Jaundice is a condition in which a person's skin and the whites of the eyes are discolored a shade of yellow due to an increased level of bile pigments in the blood resulting from liver disease. Jaundice is sometimes called icterus, from a Greek word for the condition.
IN CONTEXT: PERSONAL RESPONSIBILITY AND PREVENTION
The National Center for HIV/AIDs, Viral Hepatitis, STD and TB prevention recommends that with regard to prevention of Viral Hepatitis A:
- Hepatitis A vaccine is the best protection.
- Short-term protection against hepatitis A is available from immune globulin. It can be given before and within 2 weeks after coming in contact with HAV.
- Always wash your hands with soap and water after using the bathroom, changing a diaper, and before preparing and eating food.
SOURCE: Centers for Disease Control and Prevention (CDC)
In destinations where high standards of hygiene and sanitation may be lacking, it is recommended to stick to bottled water and avoid ice, seafood, raw fruit and vegetables, and foods sold by street venders. Personal hygiene is also essential—thorough handwashing after the bathroom and before eating or preparing food will help avoid transmission of HAV.
Despite food safety measures, outbreaks of Hepatitis A sometimes occur wherever food is prepared and served. In February 2007, an employee at a well-known catering company in Los Angeles, California was diagnosed with Hepatitis A, sparking an investigation into events the company had catered during the concurrent Hollywood entertainment industry awards season. Several celebrities and movie industry executives were contacted by health authorities, recommending immune globulin injections to prevent Hepatitis A infection after they were possibly exposed to the disease by food served during the festivities.
See AlsoFood-borne Disease and Food Safety; Hepatitis B; Hepatitis C; Travel and Infectious Disease.
BIBLIOGRAPHY
Books
Achord, James L. Understanding Hepatitis. Oxford, MS: University of Mississippi Press, 2002.
Web Sites
Centers for Disease Control and Prevention (CDC). “Hepatitis A Fact Sheet.” October 4, 2006 <http://www.cdc.gov/hepatitis> (accessed March 2, 2007).