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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 US Postal 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 “Vital moments”), 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.