THE line has been crossed. Even if those responsible for the recent anthrax mailings are caught, another attack could come without warning. So what should we do? The USPostal Service is looking at technologies that could sterilise mail, such as ultraviolet light. But terrorists could easily find another means of delivery.
Vaccinating millions of people against an attack that may never happen isn't practical. All vaccines can cause side effects, and the anthrax one doesn't give full protection against all strains.
Researchers are working on better treatments (see opposite), but at the moment antibiotics only work if given early enough. That means the key to saving lives is to detect an attack as soon as possible. But identifying anthrax isn't easy.
There are some "quick and dirty" field tests. An antibody test can give results within 15 minutes. But Bacillus anthracis is incredibly similar to its harmless and more common bacterial cousins, and it's not clear how specific the test antibodies are. That means the tests can give false positives.
It's also why the next step is usually PCR, a technique that amplifies tiny amounts of DNA. A specialised machine the size of a bread box made by Cepheid of California can now detect anthrax DNA within 30 minutes. A positive PCR result is very reliable, says Calvin Chue of the Center for Civilian Biodefense Studies at Johns Hopkins University in Baltimore.
The problem for health officials is that negative results don't prove spores were absent. Both DNA and antibody tests rely on cracking open the tough spores. But the solutions used to do this can inhibit the PCR reaction. That's why the gold standard for anthrax testing still consists of growing the bacteria in different environments. This can take days.
And the main problem with all these tests is that they are only done if an attack is suspected. What if someone manages to disperse spores over a crowd without anyone noticing? What officials would really like is a quick and easy way to test the air from a distance. Several groups are already working on "smoke detectors" for bioweapons, and remote detection from several kilometres away might be possible, too.
At the Lawrence Livermore National Laboratory in California, Page Stoutland and his team have built an antibody-based machine the size of a mailbox that sucks in air, checks for anthrax or other bacteria, and radios an alarm station if it finds anything. "The goal is to have something that sits there 24/7, detecting agents," says Stoutland.
But if there is a chance of false alarms as with other antibody tests, organisations may be reluctant to use such machines. At Johns Hopkins University, however, Wayne Bryden's team is developing mass spectrometer built into a detector the size of a large suitcase, which he says can distinguish between anthrax and its harmless relatives. He hopes to have a prototype ready soon.
For detecting bioweapons remotely, one technology that has already had some success is LIDAR, the laser analogue of radar. A helicopter-mounted system developed at Los Alamos National Laboratory fires powerful laser pulses at a suspect cloud. The reflected light reveals the size and density of the particles. If all are the same size, the cloud is likely to be artificial.
But LIDAR doesn't reveal the type of bacteria. So researchers shifted to ultraviolet wavelengths, which can yield signals unique to different pathogens up to 12 kilometres away. Still, the system cannot distinguish between anthrax and very similar bacteria. One solution may be to use super-strong laser pulses to burst the spores, releasing compounds that a detector can spot.
But these technologies won't be ready for some time. And even when detectors are available, they are not going to come cheap. Bryden's machine could cost hundreds of thousands of dollars. While key government sites and public places might install such devices, elsewhere vigilance and old-fashioned culture tests look likely to remain our main defence against anthrax.
Authors: Sylvia Pagan Westphal and Catherine Zandonella
New Scientist issue: 27 October 2001
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