Sunday, November 21, 2010

Things you need to know about hepatitis A


Prevalence of antibody to hepatitis A virus, 2006.
/ Courtesy of Centers for Disease Control and Prevention

By Yoo Youk-jin

Hepatitis A is an acute infection of the liver caused by the hepatitis A virus (HAV), which is most commonly transmitted by contaminated food or drinking water. According to the World Health Organisation, there are an estimated 1.5 million new cases of hepatitis A each year, worldwide.

It's particularly common in less developed countries with extreme poverty or poor sanitation conditions. Africa, northern and southern Asia, and parts of South America, all have high rates of the disease. In these regions almost every adult carries antibodies for hepatitis A suggesting that it is quite usual for people to be exposed to the infection, usually during childhood, and naturally develop immunity.

This is not different from what has occurred in South Korea, and it is the reason why most Koreans over 50 years in age have immunity against HAV. However, in contrast the younger Korean population are rarely exposed to the virus after birth, so they don’t have similar immunity. More than 15,000 Korean people were infected last year, and the number of reported cases is increasing rapidly every each year (7,895 cases in 2008 compared to 2,233 cases in 2007). And those most commonly infected are in their 20s and 30s, and live in Seoul, Incheon or Gyeonggi province.

Hepatitis A has some distinctive characteristics compared to Hepatitis B or C. It is an acute infection, rather than chronic. The incubation period is between two and six weeks and the average is 4 weeks. How severely someone is affected varies from case to case. Some may not show any symptoms at all, while others may have those similar to the flu. This is particularly true among infants and young children. It is known that 70% of the children with HAV less than 6 years old show no symptoms at all.

The older the patient is, the more severe the symptoms are likely to be. Possible symptoms could be fever, feeling weak, tiredness, headaches, muscle aches, nausea, vomiting, abdominal pain and diarrhea. It can lead to jaundice, which is yellowish discoloration of the skin and the whites of the eyes, because the liver becomes unable to remove a substance called bilirubin from the blood. This may explain why even a previously healthy young man needs to be hospitalized.

The good thing is, it rarely causes life-threatening liver damage. Additionally, after the infection takes place, the immune system creates antibodies against the virus that confer immunity against future outbreaks. This can also be achieved by vaccination which requires two injections, at least 6 months apart. Once people have the antibodies either through an HAV infection or by vaccination, they usually have lifelong immunity. If someone wants to know whether or not he or she needs to be vaccinated, a simple blood test for the antibodies could indicate such and it could prove a cost-effective health benefit for some adults.

Here are some tips on prevention that you may want to follow.

Avoid eating raw or undercooked salads, vegetables and shellfish.

Check whether water is safe before you drink it.

Get vaccinated against hepatitis A if you are travelling or working in countries (including South Korea) with an intermediate or high level of Hepatitis A infection.

The author is a clinical instructor at the Seoul National University Hospital International Healthcare Center (SNUH-IHC).

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