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Hepatitis A Much More Common in U.S. Than Thought

Mon May 6, 2002

By Charnicia E. Huggins

NEW YORK (Reuters Health) - Every year, a quarter of a million people in the US may become infected with hepatitis A--nearly 10 times the number of cases that are reported to the federal government. What's more, the majority of these cases may occur in children under the age of 10, a finding which may have implications for future immunization practices, according to researchers from the US Centers for Disease Control and Prevention.

Hepatitis A is a liver-infecting virus spread through contaminated food and water. It is rarely fatal and most often causes jaundice, a yellowing of the skin due to reduced liver function, and flu-like symptoms that can persist for weeks. Unlike other forms of hepatitis, it does not cause a chronic, lingering infection.

National surveys have suggested that 47 million Americans have antibodies in their body that recognize hepatitis A, meaning that these individuals were exposed to the virus at some point in their life. Yet, the number of reported disease cases have been much lower--only 26,000 a year between 1980 and 1999.

"We've always known that there are much more cases than were reported to the state health department," study author Dr. Gregory L. Armstrong, of the US Centers for Disease Control and Prevention in Atlanta, Georgia, told Reuters Health.

Doctors may not report cases to the federal government, and symptoms in children are often nonexistent or unrecognizable. For example, symptoms such as fever and diarrhea are typical of many types of illnesses, and may not even warrant a doctor's visit.

Armstrong and his co-author, Dr. Beth P. Bell, used a mathematical model to estimate actual cases of hepatitis A by taking into account underreporting by doctors and patients. Their findings are published in the May issue of the journal Pediatrics.

Based on the model, Armstrong and Bell estimate that an average of 271,000 hepatitis A infections occurred every year between 1980 and 1999, 10.4 times the actual number reported. Nearly 60% of these cases occurred in children aged 9 years and under, and only about 40% were accompanied with recognizable jaundice symptoms.

The high number of cases in children suggests that vaccinating children "should have a strong 'herd immunity' effect," such that by vaccinating one child you prevent him or her from becoming infected and from transmitting an infection to other children and adults, Armstrong said.

Armstrong noted that although it is too early to make policy changes based on the findings, "the data gives further support to the notion that immunizing children will have a big impact on reducing hepatitis A rates overall."

SOURCE: Pediatrics 2002;109:839-845.

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