THE bioterrorists have struck. After years of speculation and argument about
the threat, it is now clear that someone is sending anthrax through the post in
the US.
As New 杏吧原创 went to press, four letters containing spores had
been opened in offices in Florida, New York City, Nevada and Washington DC, at
least a dozen people had been exposed to the bacteria, one man had died of
respiratory anthrax, another was being treated for it and a woman and a child
had skin infections.
The attacks have sent waves of panic across the US and beyond. Governments
worldwide are now stockpiling antibiotics and reviewing their emergency plans.
In the long-term, there could be a strengthening of the systems for detecting
and controlling disease outbreaks of all kinds.
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But the incidents haven鈥檛 involved the large-scale release of anthrax spores
envisaged in many bioterror scenarios. The number of victims so far is tiny
compared with 751 people who became ill in 1984 when a religious cult infected
salad bars in Oregon with Salmonella. In fact, the initial incidents
nearly went unnoticed.
On 2 October, Robert Stevens, a photo editor with The Sun newspaper
in Boca Raton, Florida, admitted himself to hospital suffering from fever,
vomiting and a headache. Bacteria from his spinal fluid were sent to a state lab
in Jacksonville, where staff just happened to have taken a course in identifying
potential bioterror agents given by the US Centers for Disease Control and
Prevention in Atlanta.
鈥淲ithout that, they might have dismissed those bacilli as contamination,鈥�
says Martin Hugh-Jones, an anthrax expert at the Louisiana State University at
Baton Rouge. If the attack had happened in some other states, 鈥渨e wouldn鈥檛 even
know by today鈥�, Mohammad Akhter, head of the American Public Health Association,
told journalists last week.
Stevens had respiratory or pneumonic anthrax, the rarest form of the disease,
caused by inhaling bacterial spores. They seem to have arrived by post: spores
were later found on his computer keyboard, and a 73-year-old mail-room employee
has also developed respiratory anthrax.
Where the anthrax came from still isn鈥檛 clear. The tests carried out at
Jacksonville would have involved growing the suspect bacteria on a blood agar
plate, staining them and looking for the characteristic shape and colour of
Bacillus anthracis. But identifying the exact strain is much harder because
the differences are so slight.
Anthrax bacteria spend most of their time sitting in soil as spores. When a
grazing animal swallows or inhales the spores, they replicate explosively and
kill the animal. Then, as the corpse bleeds, the bacteria return to the soil and
turn back into spores. The bacteria spend so little time dividing that there
seems to be little chance for differences to evolve.
Soon after anthrax was identified in Florida, a private airplane whisked
samples to one of the few laboratories that can identify an anthrax strain. The
lab looks for sequences of repetitive DNA known as variable number tandem
repeats at more than 30 different places in the B. anthracis genome.
Analysis of a global anthrax collection put together by Hugh-Jones and other
researchers showed in 1998 that bacilli from different places differ slightly in
the number of repeats. This technique recently revealed that the Aum Shinrikyo
cult only failed to infect people in Tokyo with anthrax in 1993 because they
used a harmless strain
(New 杏吧原创, 1 September, p 6).
Last week, the FBI announced that Stevens鈥檚 anthrax belonged to the Ames
strain, a relatively virulent anthrax isolated in Iowa in 1932. It was the main
strain produced by the US in its bioweapons programme, which ended in 1969.
The Ames strain is native to North America, and still circulates in the wild.
There have been several recent outbreaks of animal anthrax in the US and Canada,
and bacteria similar to those that led to Stevens鈥檚 death killed a goat in Texas
in 1997.
But the Ames strain is also a lab workhorse. Versions of it exist in research
and teaching labs worldwide, and it can be bought from biological supply houses.
The US cracked down on sales of pathogens to unlicensed purchasers in 1996, but
there are few controls elsewhere.
In a security experiment last year, the US defence department gave people
with basic technical expertise $1.6 million to see if they could produce
harmless bacteria similar to anthrax. They made a kilogram, milled to a size
that would cause pneumonic infection. No other agencies spotted their
activities.
Stevens died on 5 October despite medical treatment. Antibiotics are usually
ineffective against pneumonic anthrax after symptoms appear because the bacteria
have already produced too much toxin.
Meanwhile, it was becoming clear that he wasn鈥檛 the only victim. On 25
September, a suspicious letter containing a white powder had arrived at NBC in
New York. On 1 October, the woman who opened it was treated for a rash on her
chest.
On 12 October, after the case in Florida had heightened awareness, test
results finally confirmed that she had a cutaneous (skin) anthrax infection,
which is less serious than the pneumonic form and can be treated by antibiotics
such as ciprofloxacin (see 鈥淭he price of panic鈥�). The suspect letter tested
negative, but another letter that arrived at NBC on 18 September from Trenton,
New Jersey, had contained spores.
A baby boy has also been diagnosed with cutaneous anthrax after visiting
ABC鈥檚 New York newsroom on 28 September, but the source isn鈥檛 clear. Spores were
also sent from Malaysia to a Microsoft branch in Reno, Nevada, and another
anthrax-containing letter postmarked Trenton was sent to the office of Senator
Tom Daschle.
No one has yet said if the bacteria found in Florida, New York, Nevada and
Washington DC all belong to the same strain. 鈥淭he exact same bacteria can cause
both cutaneous and inhaled forms of the disease,鈥� says Phil Hanna of the
University of Michigan at Ann Arbor, so there could be a common source. The FBI
and anthrax researchers will need to do a lot more detective work to find out
where the anthrax came from and who was responsible.
Until now, many experts have argued that the difficulty of obtaining and
administering germs made bioterrorist attacks unlikely. That argument no longer
applies.
As Michael Osterholm, a former state epidemiologist for Minnesota, told a US
Senate committee last week: 鈥淪omeone had anthrax. Someone could put it in a
position to do what it did.鈥� The job for health authorities now is to get better
at spotting and responding to bioterror before a more deadly attack is launched.
HOARDING antibiotics in case of an anthrax attack won鈥檛 help you, and might
well end up harming you and other people.
Anyone suspected of having come into contact with anthrax spores is
immediately prescribed a course of antibiotics. If infection is not spotted
until the flu-like symptoms of respiratory anthrax appear, as happened with the
first case in Florida, it鈥檚 usually too late for antibiotics to help.
Either way, there鈥檚 no point keeping a private stash of drugs. Yet that it is
exactly what鈥檚 happening across the US, in spite of numerous requests from
health authorities for people not to hoard the drugs.
Sales of ciprofloxacin or Cipro, the antibiotic of choice against anthrax,
have soared in the past few weeks, both online and in pharmacies. But people
taking the antibiotic 鈥渏ust in case鈥� of an attack risk damaging their health.
鈥淭he side effects can be serious and long lasting,鈥� says Luciana Borio, a
physician at the Johns Hopkins Center for Civilian Biodefense Studies in
Baltimore. They may include convulsions and cartilage damage.
There鈥檚 also the worry that overuse will encourage bacteria to develop
resistance. 鈥淭he concern is that as everyone takes Cipro, we鈥檙e going to lose it
as a therapeutic agent,鈥� says Stuart Levy of the Center for Adaptation Genetics
and Drug Resistance at Tufts University in Boston.
Cipro is a powerful antibiotic that kills many kinds of bacteria, and we鈥檙e
running out of drugs like this, Levy says. 鈥淲e鈥檙e left with a few drugs we can
count on, and Cipro is one of them.鈥� Most anthrax strains, including the one
that killed in Florida, are susceptible to a range of antibiotics, including
penicillin.
All that鈥檚 needed for other diseases to evolve resistance is for a large
number of people to take the antibiotic at the same time, he says.
Cipro-resistant strains of diseases such as gonorrhea are already emerging
worldwide.
鈥淚t鈥檚 a simple message: you overuse it and it will cause resistance,鈥� Levy
says. If you get Cipro, you should lock it up and not use it unless health
authorities say so, he adds. Sylvia Pag谩n Westphal, Boston