A federal air monitoring system designed to monitor threats to human health in the Puget Sound region recently identified bacteria that can cause tularemia, an infectious disease, in a daily air sample taken from a monitoring station in east King County. Bacteria levels were low, close to the detection limit, and a subsequent test found no bacteria present.
Since the air monitoring system was established nationally in 2003, similar positive test results due to naturally-occurring bacteria have been common in other areas of the country.
The bacteria, Francisella tularensis, are found throughout Washington, commonly carried by rabbits, squirrels and other rodents. People rarely are infected with tularemia; only two cases have been identified in Washington this year. Typically, Washington sees between one and 10 human cases per year.
The positive sample came from a filter collected the morning of Monday. As soon as the bacteria were identified, officials immediately collected a subsequent sample from the same station ahead of schedule Monday evening, which was negative. Health and safety officials continue to monitor the situation.
State and local officials agree the detection shows the public health response plan worked. The air monitors detected bacteria even though levels were low, state and local health teamed with law enforcement and confirmed there’s no threat, and research showed no signs of illnesses reported in the area. Notice has been sent to area health care providers.
The air monitoring system that detected the bacteria is called BioWatch, a federal program that operates nationwide in major metropolitan areas. The program routinely collects air samples and tests them for trace amounts of biologic material that could be due to either an intentional attack or a natural occurrence.
There are several monitors located throughout the Puget Sound area in King, Pierce, and Snohomish counties. This is the first time that a sample from the Puget Sound area has tested positive. Locations of the monitors are withheld for security purposes.