Barbara Boughton

September 21, 2009

September 21, 2009 (San Francisco, California) — The hepatitis E virus has become increasingly problematic in developing countries and in the developed world, according to a presentation here at the 49th Interscience Conference on Antimicrobial Agents and Chemotherapy.

A recent study published in the Journal of Infectious Diseases (J Infect Dis. 2009; 200:48-56) found that 21% of the American population may have been exposed to the virus, according to researcher Kenrad Nelson, MD, professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland.

The hepatitis E virus was first identified in the late 1980s. The 2009 study showed that the seroprevalence of hepatitis E, assessed for the first time from 18,695 serum samples collected in the Third National Health and Nutrition Survey between 1988 to 1994, was already above 20% roughly 20 years ago, Dr. Nelson noted.

Those who had the highest levels of exposure were individuals born in Mexico, immigrants from Mexico, and those who lived in the Midwest. People who ate liver or other organ meats more than once a month were also more likely to be positive for hepatitis E, Dr. Nelson said.

"We're still a little puzzled about why there was such a high prevalence of antibodies to hepatitis E in the population, and one explanation may be that these infections are asymptomatic," Dr. Nelson said.

In the developed world, reports have surfaced about farmers getting ill from hepatitis E after contact with pigs, and a few cases have resulted from people eating pig organs and sushi made from deer.

There are 4 genotypes of hepatitis E: 2 are zoonotic infections and 2 genotypes are primarily caused by fecal contamination of water supplies. In fact, the first epidemic of hepatitis E occurred in Delhi, India in 1955 when a monsoon rain caused the sewage system in the city to contaminate the local water supply.

How people in the developed world are exposed to the virus remains something of a mystery. Dr. Nelson speculated that contamination of farming fields by pig manure containing the virus is one explanation. In the developed world, hepatitis E is primarily a concern for people who are immunosuppressed, he said. A small number of cases involving organ-transplant recipients have been described, but these were quite serious — the patients went on to deliver chronic hepatitis, Dr. Nelson said.

Hepatitis E is a significant danger in the developing world, particularly for pregnant women. "There are outbreaks almost every year in India and Pakistan, with tens of thousands of cases of hepatitis," Dr. Nelson said. "In Bangladesh, it's been estimated that 13% to 15% of pregnant women who die, die from hepatitis, and we think that most of this is hepatitis E," he said.

Hepatitis E has been sequenced, and it's usually detected by PCR. GlaxoSmithKline has developed a vaccine for 1 genotype of the virus, and although studies have proven it to be effective, Dr. Nelson said the company has declined to develop or manufacture it because the primary markets are Pakistan, Nepal, India, Burma, and Bangladesh.

"It's not economically feasible. We have been hoping that we can get some international support to push this orphan vaccine forward or that another vaccine will be developed," he said. "To me, this is a public health emergency that's not being dealt with," he said.

Other researchers agree that the problem of hepatitis E is a significant one. "Hepatitis E remains highly endemic in the developing countries of Latin America, Africa, Asia, and the Middle East. A major cause of concern is acute [hepatitis E infection] in pregnant women, especially in the third trimester of pregnancy, when it can be associated with 15% to 25% mortality," noted M. Rizwan Sohail, MD, assistant professor of medicine and an infectious disease specialist at the Mayo Clinic in Rochester, Minnesota. "In the absence of any effective treatment options, preventive efforts need to focus on a clean drinking water supply and the development of an effective vaccine," he said.

Dr. Nelson and Dr. Sohail have disclosed no relevant financial relationships.

49th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC): Presentation 487. Presented September 13, 2009.