ARENAVIRUS INFECTION LINKED TO DEATHS IN CALIFORNIA

The discovery followed an extensive investigation by the California Department of Health Services (DHS) and the University of Texas Medical Branch (UTMB) into the unexplained deaths of a 52-year-old female who died in June 1999 in Riverside County, a 14-year-old female who died in April 2000 in Alameda County and a 30-year-old woman who died in June 2000 in Orange County.  UTMB has one of the few laboratories in the country equipped to test for arenaviruses. 

In the 14-year-old patient, arenavirus has been confirmed and in the two others, the virus is highly suspected based on initial laboratory tests.  Further testing is under way.  The three individuals were each hospitalized with fever and respiratory distress.  Two of them also had severe liver disease and bleeding consistent with viral hemorrhagic fever. 

Like hantavirus, which causes a rare, but often fatal respiratory disease, arenaviruses are believed to be transmitted to humans through inhalation of dust contaminated with the urine, feces or saliva of infected rodents.  Human infection with arenavirus is also likely to be very uncommon.  Arenavirus infection has been documented in rodents in Southern California in recent years. 

"Viral hemorrhagic fever associated with arenaviruses has never been documented in the United States except among overseas travelers and laboratory personnel exposed accidentally while doing research," Bontá explained. 

DHS was prompted to send specimens to UTMB because of clinical and autopsy findings suggestive of viral hemorrhagic fever and a history of rodent contact in the Riverside County patient.  The virus was detected in all three patients through testing for virus genes.  In addition, virus isolation was used to confirm infection in the 14-year-old.  There is no evidence that these cases are related. 

In parts of Africa and South America, several arenaviruses are known which cause mild to severe infection characterized by fever, headache and occasionally severe bleeding or nervous system problems.  Lassa fever and the South American viral hemorrhagic fevers are examples of human illnesses caused by such arenaviruses. 

The antiviral drug ribavirin has been successfully used in the treatment of other arenavirus infections.  Studies are under way to learn more about this virus and medicines that may be effective. 

Individuals can protect themselves from diseases carried by rodents by taking some relatively simple precautions both in the home and while outdoors: 

·        Do not touch or feed wild rodents or any other wild animals. 

·        Properly dispose of trash and clutter; move woodpiles away from residences. 

·        Prevent rodents from entering residences by blocking holes; control rodents with spring-loaded (snap) traps. 

·        Store food and garbage in rodent-proof containers; pet food should not be left outside. 

      ·        Avoid creating dust when cleaning buildings with signs of rodent infestation.  Wet the area thoroughly with a disinfectant like bleach and use gloves to clean up.  Contact local public health officials for recommendations about safely cleaning rodent-infested areas. 

·        Cabins and buildings that haven't been occupied for some time should be aired out.  If possible, buildings should not be used if there are signs of rodent infestation until properly cleaned. 

·        When sleeping outdoors, avoid campsites near rodent droppings, burrows or nests.

ARENAVIRUSES Q & A

What are arenaviruses? 

Arenaviruses are infectious agents carried by rodents that cause human illness similar to hantavirus.  In parts of Africa and South America, several arenaviruses are known which cause mild to severe infection characterized by fever, headache and occasionally severe bleeding or nervous system problems.  Lassa fever and the South American viral hemorrhagic fevers are examples of human illnesses caused by such arenaviruses.  In the United States, arenaviruses have been found in several types of rodents, including woodrats, cotton rats and common house mice. 

What are the symptoms of arenavirus infection?

Initial symptoms may be relatively mild and nonspecific and may include fever, muscle aches, weakness, malaise and dizziness.  They can progress to severe life-threatening diseases, including bleeding, shock and central nervous system involvement. 

Who is at risk for infection and illness from these viruses? 

In general, rodents are natural carriers are arenavirus.  Humans may become infected through contact with the feces, urine or saliva of infected rodents.  They also can become infected by breathing tiny air-borne particles that have been contaminated with the feces, urine or saliva of infected rodents. 

What do we know about the three cases in California? 

One case has been confirmed; two are highly suggestive.  Initial symptoms were flulike.  All cases progressed to significant respiratory distress.  Two of the individuals developed liver failure and severe bleeding. 

How is a diagnosis of arenavirus made? 

Scientists analyze a sample of body fluids or tissue, trying to identify genes specific to the virus.  In addition, scientists try to detect antibodies to arenavirus, stain tissues for evidence of the virus or isolate the virus in tissue culture. 

Is there any treatment for arenavirus? 

Treatment for infection with arenaviruses is mainly supportive.  Specific therapy with ribavirin, an anti-viral drug, has been shown to be effective in treating some African and South American arenavirus infections. 

What can I do to protect myself from arenaviruses? 

·        Do not touch or feed wild rodents or any other wild animals. 

·        Properly dispose of trash and clutter; move woodpiles away from your residences. 

·        Prevent rodents from entering residences by blocking holes; control rodents with spring-loaded (snap) traps. 

·        Store food and garbage in rodent-proof containers; pet food should not be left outside. 

·        Cabins and buildings that haven't been occupied for some time should be aired out.  If possible, buildings should not be used if there are signs of rodent infestation. 

·        Avoid creating dust when cleaning buildings with signs of rodent infestation.  Wet the area thoroughly with a disinfectant like bleach and use gloves to clean up.  Contact local public health officials for recommendations about safely cleaning rodent-infested areas. 

·        When sleeping outdoors, avoid campsites near rodent droppings, burrows or nests. 

What is the California Department of Health Services doing about arenavirus? 

The investigation into the three cases is continuing.  This effort includes additional testing of case specimens, review of clinical and laboratory data, review of exposures and field investigation.  The health care community is being educated about arenavirus.  Surveillance of rodents throughout the state is continuing to better delineate the geographic distribution of arenavirus.

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