California health officials said on Thursday that they have linked three recent unexplained deaths to a rare virus, normally carried by rodents, that has almost never before infected humans in North America.
One week prior to the California cases, a 48 year-old surgeon who was infected with Lassa fever virus while working in Kenema, Sierra Leone died while undergoing treatment at Leiden University Hospital, The Netherlands. The man was initially treated for malaria in Sierra Leone on 11 July, and then traveled to The Netherlands (arrived 14 July) to visit relatives. He was admitted to the hospital on 15 July. Lassa fever was suspected when his condition worsened on 20 July and treatment with ribavirin was started. On 22 July, the Bernard Nocht Institute for Tropical Medicine in Hamburg, Germany reported that Lassa virus was detected in a blood sample sent for diagnostic testing. The man's potential contacts are being traced and monitored in both The Netherlands as well as in Africa.
The so-called "arenavirus," which causes potentially fatal respiratory disease, is transmitted to humans through inhalation of dust contaminated with the urine, feces or saliva of infected rodents.
Variations of the virus are often seen in human populations in Africa and South America, scientists said. Arenavirus has also been documented recently in rodents in Southern California. However, until now it had never been seen in humans anywhere in the US, "except among overseas travelers and laboratory workers exposed accidentally while doing research," California Health Director Diana Bonita said in a statement.
The California virus was detected through genetic testing of three Southern California women who died in the last 14 months. Among the victims were a 30-year-old who died last month in Orange County, a 14-year-old who died in April in Alameda County, and a 52-year-old who died in June 1999 in Riverside County. The 52-year-old woman had a history of contact with rodents.
Each had been hospitalized with fever and respiratory distress. Two of the women also had severe liver disease and bleeding. Initially their cause of death was unexplained. There is no evidence that the cases are related, and human infection with arenavirus is expected to be uncommon in the US, health officials said.
In order to avoid the virus, people are encouraged not to touch or feed wild rodents or any wild animals; to properly dispose of and contain trash; to avoid camping near rodent droppings, burrows or nests; and to avoid creating dust when cleaning rodent-infested areas by first wetting the areas with bleach.