Late at night in the Boston area subway system, researchers release a cloud of bacteria into the tunnel?
Editorial: "The impossibility of total vigilance against terrorism"
IT'S 3 am, and the subway station has long since shut for the night. As I watch, a small group of people move along the platform in the eerie quiet, their anticipation palpable as they prepare to release a cloud of bacteria into the tunnels beneath the densely populated Boston area.
Among them is a woman holding an array of translucent green nozzles, ready to release the agent. Her radio crackles to life: "The train has just left; we're a go."
Anne Hultgren isn't a terrorist: in her hands she holds a batch of dead Bacillus subtilis bacteria which, when dispersed, will form nothing more than a harmless cloud. It's all part of an experiment by Hultgren's employer, the US Department of Homeland Security (DHS). Her team is testing whether its new detection equipment could work as an early warning system if a deadly agent like anthrax was released into a city's metro network.
The faint rumble of the inbound train gets louder, and Hultgren starts spraying. Almost immediately, the cloud begins to waft through the tunnel towards downtown Boston, pushed by a column of air in front of the train.
As the train pulls in to the station we watch and wait to see if the sensors at the next stop down the line will detect the bacteria.
At our station, several bulky grey sensor boxes called triggers are slung on metal racks at four points along the platform. The triggers were installed around a year ago and since then have been measuring background levels of biological material - one of the keys to avoiding the false positives that have dogged previous biosensing systems. Hultgren can't go into detail about the technology inside, but similar commercially available systems count biological particles as they pass through a beam of light inside the box.
Anything over the background level will send a signal that activates a bright red box at the end of the station. Hultgren calls it a confirmer, and says it is the real novel technology in this test.
Hultgren and her team were brought in to improve the beleaguered BioWatch programme (see "Crying wolf on terrorism"), and the confirmer is the result. She says that her team has miniaturised the equipment needed for a process commonly used to identify DNA, called the polymerase chain reaction.
"Previous biodetection programs relied on continuous daily testing," Hultgren says. "Air filters would be collected every day by hand, and brought to a lab for analysis."
That lab analysis has now been engineered into a suitcase-sized box, and happens on site whenever the triggers detect unusual quantities of a biological agent. "We are aiming to do in 20 minutes what used to take two days," Hultgren says.
A few days after the test, Hultgren tells me the system worked as planned, both detecting and identifying the bacteria. "The confirmer collected a sample and about 30 minutes after the release we had a positive detection of the material at a station over a mile away down the track," she says.
The tests will continue for five months, helping the DHS understand how biological agents move around the subway when the weather is colder, for instance.
Janet-Martha Blatny, who runs a similar biosensing project for the European Commission, says that tests like this are crucial to improving biodetection systems.
"Trials resembling real-life conditions have been lacking and are one of the major causes explaining the high rate of false alarms of current biodetectors," Blatny says.
Crying wolf on terrorism
In the wake of 9/11, letters laced with anthrax bacteria began showing up, delivered through the US postal system. Five people died in the attacks. In response, the government launched an anti-bioterror programme in 2003 called BioWatch.
BioWatch has sensing systems in major cities across the country. Since its deployment, it has been plagued by false alarms and has never spotted an instance of terrorism. Lawmakers have grown critical that the $1-billion programme risks desensitising officials, who may not react if the system detects a real attack.
Congress is currently deciding whether to spend an extra $3.1 billion over the next five years to keep the programme going.
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