Doctors still trying to diagnose mysteries of hantavirus

The CDC has tracked every case of hantavirus pulmonary syndrome across the U.S. since it was first identified in the country in 1993. That year, 48 people became ill. From 1994 to 2011, an average of 28 people got the disease each year. Above, a researcher from the University of New Mexico, shown in this 1996 photo, weighs a mouse caught in traps during a study of hantavirus. (Paul Bearce, Associated Press /January 1, 1996).

By Kate Mather and Anna Gorman, Los Angeles Times

Nearly 20 years after hantavirus was first identified in the U.S., doctors are under pressure to quickly learn more about the pervasive and deadly disease.

In his 30-plus years as a doctor, Bruce Tempest had never seen anything like it.

A Navajo man having trouble breathing showed up at the emergency room of a small hospital in Gallup, N.M. Less than an hour later, he was dead. The man had been young, athletic and otherwise healthy. His fiancee had died days before, also from sudden breathing problems.

"This is something different," Tempest, now 76, remembered thinking of the 1993 illnesses. "It just doesn't fit."

Tempest contacted area doctors, looking for other cases. Then he asked the University of New Mexico for help. Soon, the patients were being airlifted to Albuquerque. They arrived with chills and aches but soon were in complete respiratory distress. Physicians were at a loss: Was it sepsis?Influenza? Bubonic plague?

Doctors had confronted a medical mystery, and they knew it had to be solved quickly. Patients were showing up at the hospital "not feeling well one day and being dead the next," said Gregory Glass, an epidemiologist at Johns Hopkins University.

When the cases hit television, a lucky clue came in. A doctor called and said the illness sounded a lot like a virus he had observed in Korea in the 1950s. It was called hantavirus.

This summer's hantavirus outbreak in Yosemite National Park has served as a sobering reminder: Mystery still surrounds the disease.

"The biggest mystery is we don't have a good explanation," said Barbara Knust, a Centers for Disease Control and Prevention epidemiologist. "For Yosemite, why this year of all years is there an increased number of cases?"

Nearly 20 years after being identified in the U.S., hantavirus is better understood but no less vexing. Researchers now know it causes hantavirus pulmonary syndrome, a severerespiratory disease. It is transmitted through the droppings and urine of deer mice, and not through person-to-person contact. Treated early, patients have a better chance of survival. But there is no cure, and more than one-third of patients die.

The Yosemite cases follow the pattern: Three of the eight visitors who fell ill died. Officials have called the outbreak unprecedented — more than one hantavirus infection from the same location in the same year is very rare.

The National Park Service has closed the cabins believed to be at the heart of the outbreak. State and federal scientists are scouring the park, trapping mice and conducting laboratory tests. Public health officials are warning doctors worldwide to watch for possible symptoms, which can be confused with the flu and can take weeks to show up.

And the California Department of Public Health said the risk of new cases remains, even as the summer surge of visitors wanes....moreover