Woman’s Death Tied to Rare Virus

State health officials are linking the death of an Orange County woman and two others over the past 14 months to a rare virus carried by rodents that has seldom been known to have infected humans in North America.

The three cases were isolated and are not believed to be related, state health Director Diana M. Bonta said. All the women are believed to have acquired the virus after exposure to rodents.

“This is a rare event, and we don’t want to get everybody all excited,” said Lea Brooks, a department spokeswoman. But people who come into contact with rodents should be concerned about exposure to this and other viruses, such as the hantavirus, which also has caused deaths in recent years.

The discovery highlights the growing concern among virologists about the spread of rare viruses globally by increased travel. The AIDS epidemic is the best-known example of a once-isolated virus from Africa spreading worldwide, and researchers fear that others will follow its course.

Rodent infections with the new virus, called arenavirus, have been documented in Southern California in the past few years, Brooks said, but human infections have been observed only in travelers returning from overseas and in laboratory personnel accidentally exposed while doing research.

Arenaviruses--from the Latin arena, or sand, because of their granular appearance--cause hemorrhagic fever, which is characterized by fevers, respiratory distress, internal bleeding, liver damage and other problems. Left untreated, the infection is often fatal. The antiviral agent Ribavirin has shown some effectiveness against infections.

The most famous member of the class of arenaviruses is the Lassa virus, a deadly infection that has been found only in Africa. About 16% of its victims die. More deadly is the Machupo virus, which produces Brazilian hemorrhagic fever and kills 60% of victims.

Pathologist Chuck Folhorst of the University of Texas Medical Branch in Galveston, where the three new cases were studied, identified the virus as the Whitewater Arroyo strain, named after the New Mexico location where it was first identified in rodents in 1996. Researchers have not reported any previous human infections with this strain.

The first victim was a 52-year-old woman who died in June 1999 in Riverside County. The second was a 14-year-old girl who died in Alameda County in April of this year, and the third was a 30-year-old who died in Orange County in June. Health department officials are not releasing the names or any other information about the women, but there were apparently no links among them.

The presence of an arenavirus has been confirmed in the 14-year-old patient and is highly suspected in the two others because of preliminary laboratory results. Testing for the virus was conducted at the University of Texas because it has one of the few laboratories in the country equipped to do so.

Dr. Carol Glaser of the state health department said there may have been other cases that have slipped through the cracks because the virus was not identified, but not large numbers of them.

Arenaviruses are carried by rodents, which do not become diseased, and spread in their urine and droppings. The virus is transmitted to humans when dried urine or droppings are stirred up and inhaled. The virus can be passed from human to human, but that is rare.

Glaser said the state will step up its rodent monitoring programs.