Emerging diseases. New arenavirus blamed for recent deaths in California.

Researchers say a new virus that appears to cause hemorrhagic fever is endemic--but at very low levels--in the western United States. Last week, the California Department of Health Services announced that a recently discovered virus carried by wood rats and pack rats killed a 14-year-old girl in April; moreover, the department says, there's strong evidence that the virus has caused at least two other deaths within the last 14 months. Experts say there is no cause for alarm, however, as they believe it to be a rare event.