By Don Finley - Express-News
Web Posted: 06/22/2010 12:00 CDT
Two local cases — one of them fatal — of a form of hepatitis once thought to be rare in the United States have captured the attention of state and local health officials.
Hepatitis E, a viral infection of the liver, was long considered a problem mainly in developing countries — and to a handful of Americans who traveled there — spread by contaminated food and water.
While the infection clears up on its own in most people, it causes severe illness in some and can be fatal in pregnant women.
Large outbreaks of hepatitis E have taken place in Mexico, Asia and Africa.
The Metropolitan Health District was notified late last year that three people in one San Antonio hospital had tested positive for the infection between September and November 2009. A more sophisticated test later found one of the three was not infected.
Of the two others, one was a 21-year-old woman who died while undergoing a liver transplant. An earlier home pregnancy test had been positive, but she wasn't pregnant when admitted to the hospital, health officials said. The other patient, a 44-year-old nurse's aide, had also suffered some liver damage.
“We couldn't figure out how they acquired it,” said Roger Sanchez, senior epidemiologist with Metro Health, who presented a paper on the cases at a public health meeting in Austin recently. “None of them had any (foreign) travel history. They were previously healthy. Which begs the question — how did they get it?”
But some American researchers who study hepatitis E are finding it more common in the U.S. than previously thought. In fact, the infection seems to be everywhere. What remains a mystery is why some people get sick from the virus but most don't.
“It appears to be a relatively common infection. But clinical symptoms following infection appear to be quite rare,” said Mark Kuniholm, an instructor of epidemiology and population health at the Albert Einstein College of Medicine in New York.
In a study published last July in the Journal of Infectious Diseases, Kuniholm and colleagues tested 18,695 blood samples that had been collected across the country through the National Health and Nutrition Examination Survey, which is conducted every few years by the federal government. He found one in every five people had antibodies to hepatitis E, suggesting a previous infection.
Setting aside those born in another country, the highest infection rates were in Anglo men living in the Midwest. Those who ate liver more than once a month were more likely to have antibodies.
Hepatitis E is commonly found in U.S. pigs, with one study showing 63 percent of commercially raised swine carried antibodies to the virus and 35 percent had signs of active infection. Another study found the virus in 11 percent of pig livers sold in a sample of grocery stores.
“But this virus doesn't make pigs very sick,” Kuniholm said. “And for the most part it doesn't make humans very sick. It appears that we get the virus, we develop an immune response, but the vast majority of us never get sick.”
Sanchez and Kuniholm stressed that proper cooking kills the virus.
Of the three common forms of hepatitis in the United States, A, B and C, the infection most resembles hepatitis A — which is also often spread through fecally contaminated food and water. Patients who get sick usually recover without treatment. But it's also different from hepatitis A in that person-to-person transmission isn't common with hepatitis E, and outbreaks are usually linked to water supplies contaminated by sewage. Adults are more likely to get sick from E, while children seem more susceptible to A.
And hepatitis E can be passed from animals to humans. A study found that American veterinarians who specialized in swine had higher rates of hepatitis E exposure. Antibodies also have been found in other animals, including rodents, dogs and cats.
Sanchez said there's too little information about the disease to draw any conclusions about whether more people are getting infected. It might be that the commercially available antibody test is prone to false positives. Hepatitis E isn't part of the standard panel of hepatitis tests given to liver patients. It must be specially ordered from certain labs.
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