Oct 10, 2003 (CIDRAP News) Air monitoring devices in Houston recently picked up fragments of the bacteria that cause tularemia, but no human cases of the disease have been found, Houston health officials reported yesterday.
The findings apparently mark the first time the new federal "BioWatch" program for detecting airborne pathogens has found signs of a "Category A" agenta pathogen considered to be an attractive weapon for bioterrorists. The BioWatch program, launched last winter, is a federal effort to monitor the air for such pathogens in about 20 large urban areas around the nation.
Low levels of the tularemia organism (Francisella tularensis) were found on filters taken from air monitors Oct 4, 5, and 6, according to a news release from the Houston Health and Human Services Department. But the pathogen was not found on filters tested Oct 7 and 8, the department said.
"The new technology in use throughout Houston and Harris County gives us information that was not previously knowable," said M. desVignes-Kendrick, MD, MPH, director of the health department. "We are investigating to determine if the bacteria was always present or newly present and if it represents a health threat to the community."
The news release said no human cases of tularemia had been found, and "there is nothing to indicate an intentional release of the organism," but officials are investigating to determine if there is a natural explanation for the test results. The disease has an average incubation period of 3 to 5 days.
Steps being taken by city and county health agencies include increased surveillance for human illness, increased environmental sampling, collection and testing of wild rabbits and rodents, and an assessment of activities that may have caused the sensors to pick up the organism, officials said.
Tularemia occurs mainly in small and medium-size mammals, such as rabbits, hares, beavers, muskrats, and prairie dogs (see CIDRAP overview of tularemia). People can contract the disease from tick and deerfly bites and from infectious animal tissue. In the 1990s, an average of 124 human cases of the disease were reported annually in the United States. The disease is not known to spread from person to person.
Tularemia in humans can range from mild to life-threatening. Before antibiotics were available, the disease was fatal in about 7% of cases; today the case-fatality rate is about 2%
Houston Department of Health and Human Services news release
Feb 26, 2003, CIDRAP News report on the federal BioWatch program