Oct 3, 2005 (CIDRAP News) Several air sensors detected traces of the tularemia pathogen on the Capitol Mall in Washington, DC, Sep 24 and 25, but no cases of illness have been reported among people who were in the area at the time, according to health officials.
In a Sep 30 message to health agencies, the Centers for Disease Control and Prevention (CDC) said environmental air monitors in the Capitol Mall "signaled the low level presence of Francisella tularensis," the bacterium that causes tularemia.
The microbe is one of the six agents considered most likely to be used by terrorists as a biological weapon. But Department of Homeland Security (DHS) officials said the pathogen probably was a natural occurrence and not the result of bioterrorism, according to a Washington Post report.
Tens of thousands of people were on the mall Sep 24 for antiwar demonstrations and the National Book Festival, according to the Post. But no cases or suspected cases of tularemia have been reported, CDC spokesman Von Roebuck told CIDRAP News today.
The air samples that yielded the findings were collected between 10 a.m. Sep 24 and 10 a.m. Sep 25, the Post reported. The air monitors are part of the federal BioWatch program, which monitors the air for pathogens in major cities around the country. The Post said Washington area health officials were notified of the findings on Sep 30.
After tests in Washington detected the pathogen on air filters, further tests were done by the CDC in Atlanta, according to the Post.
Roebuck said today he didn't know yet what quantity of the agent was found or what strain of tularemia it was.
"We're looking to find out if anyone in the medical community has any patients with symptoms that could be similar to tularemia," he said.
The CDC notice said the usual incubation period for the disease is 3 to 5 days, suggesting that anyone exposed around Sep 25 would have become ill by today. But in rare cases symptoms can take longer to appear, the agency said.
The United States had an average of about 124 cases of tularemia per year in the 1990s, most of them occurring in rural areas. Tick bites and handling of infected animals are the most common routes of infection, but people can also contract it from insect bites, eating or drinking contaminated food or water, or inhaling the bacteria, according to the CDC.
The disease can cause several different clinical syndromes, depending on the route of infection. The CDC notice said inhalation of the microbe is most likely to lead to pneumonic, oculoglandular, or oropharyngeal disease. Tularemia does not spread from person to person, and it can be effectively treated with antibiotics. But it can be fatal in some cases.