BioWatch program aims for nationwide detection of airborne pathogens

Editor's Note: The text as originally published on Feb 26 was revised slightly on March 10, 2003.

Feb 26, 2003 (CIDRAP News) – Typical predictions about what would happen in a bioterrorist attack with airborne germs say that no one would know about it until a number of people with similar symptoms starting showing up in clinics and emergency rooms. But the federal government is hoping to change that scenario with its new nationwide program to sniff the air for dangerous pathogens.

The "BioWatch" program is an ambitious effort to sample the air in major metropolitan areas daily for pathogens that terrorists might use, according to federal officials. Testing equipment is being set up in 20 metropolitan areas, according to a Department of Health and Human Services (HHS) public relations spokesman in Washington, DC. An air monitoring program used during the 2002 Winter Olympics in Salt Lake City was the prototype for the system.

"The ultimate goal is to deploy these in various cities so that 80% of the American population by geographic distribution will be living in areas that will be covered by this equipment," the HHS spokesman, who asked that his name be withheld, told CIDRAP News.

The system involves the installation of special paper filters on existing Environmental Protection Agency (EPA) air-quality monitoring stations, the spokesman said. Plans call for removing each filter every day, taking it to a laboratory, and using a polymerase chain reaction (PCR) analysis to test it for pathogens that terrorists might use.

"Early detection is the key to getting a jump on a biological incident," said the HHS official. "They'll be collecting these filters daily, seven days a week." He said that from the time a filter reaches the lab for analysis, it will take from 3 to 8 hours to rule out pathogens or identify one, depending on what it is.

Federal officials say the initial focus of the monitoring includes a short list of agents that terrorists are considered likely to use. The HHS spokesman said the laboratories involved, all part of the CDC's Laboratory Response Network, can test for a wide variety of pathogens, and different labs might look for additional pathogens.

Each urban area will have 10 to 12 air monitoring stations, the HHS spokesman said. He said $40 million has been earmarked for the program for fiscal year 2003, enough money to deploy the sampling equipment in the 20 cities and cover some additional expenses.

Officials involved with BioWatch acknowledge that the system's existence prompts tough questions about what to do when pathogens are found. How will authorities know if a positive finding is a true-positive? If it is a true-positive, how can analysts assess whether it represents an isolated natural event or a terrorist attack? And if the finding does seem to represent an attack, how should authorities respond?

While offering few details, the HHS spokesman said authorities in the various cities are working on plans for responding to any findings that indicate a real danger. "In each of the local metropolitan areas they've set up a working group with the local FBI office and they're working on a game plan on how they're going to handle the analysis that comes out of the system. Each of the areas is going to be doing some tabletop exercises to practice how they'll handle it when they get results they need to act on."

The public health laboratory director in one of the states affected said the possibility of false-positives is a big concern. "When we apply these kinds of tests, we'd like to be able to culture the organisms as well," to confirm any positive results, he said. But this isn't a good option because the air sampling units use high-speed airflow that would tend to kill most organisms through shearing forces and drying, he said. Spore-forming organisms would probably survive, but most others would not, he said.

Also complicating the picture is the natural occurrence in some areas of pathogens that terrorists might use. A positive test result might be accurate without being evidence of a real problem. "A lot of factors would have to be taken into consideration" in interpreting a finding, the laboratory director said."The last thing you'd want to happen would be to put out a false alarm."

The air monitoring program during the 2002 Winter Olympics included one episode that gave a preview of the kinds of questions that can arise, according to Scott Williams, MD, deputy director of the Utah Department of Health.

Williams said the program involved 15 to 20 monitoring stations scattered over a large area centered on Salt Lake City. The filters were removed every 4 hours and tested for the presence of pathogens in the CDC's category A. The lab analysis began with a screen for a single strand of DNA, he explained. If that test was positive, a second single-strand test was done; a second positive finding prompted a confirmatory test looking for four different DNA strands. The lab analysis was handled by the US Department of Energy (DOE), which developed the special PCR tests involved.

"There was one event that created sort of an initial posturing of response," Williams said. On Feb 12, 2002, a sample collected at the airport came up positive on more than one single-strand test. "We alerted the airport that they may need to evacuate," he said. But officials decided to wait for the confirmatory test before taking that step. That turned out to be the right move, because the confirmatory test showed that the microbe was a cross-reacting organismÑa nonpathogenic one with a DNA strand that matched a strand in one of the pathogens being sought, Williams said. (Officials never were able to identify the organism; it was assumed to be "just an endemic organism that happened to share that single strand," he noted.)

Before the alarm was called off, the airport started preparing to close, and hazardous-materials teams were suiting up for possible duty, Williams said. "It was interesting because it created all of the scientific and political response processes. . . . It was the most realistic tabletop exercise you could have conducted."

Williams said Utah health officials took some lessons from the episode. In the interest of quicker confirmation or rejection of positive test results, "We recommended to DOE that they change the [PCR testing] process so that they always run the four-strand confirmatory test simultaneously with the second single-strand test."

The event also pointed up the importance of tabletop exercises simulating this type of scenario. "We did a lot of tabletop exercises before the Olympics, but we never specifically mock-exercised the air monitoring event," Williams said. "We were able to create a good decision process as we went, but it wasn't as comfortable as it could've been."

Also, even with careful planning, potential threat situations inevitably involve people who never participate in tabletop exercises, he added. "So we realized that what you need is a very rapid briefing process for these people, so they're not trying to figure out what you're talking about while they're trying to make a decision about whether to close the airport."

HHS and the CDC are the lead agencies on the BioWatch program because it's a bioterrorism issue, according to the HHS spokesman. "But we couldn't have done it without the DOE's assistance with the filters and the testing, and EPA has been key in getting it set up and collecting the filters," he said.

"It's going to be very labor-intensive," the laboratory director said in describing the effort. "It'll also be very routine, until you get a positive."

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