Anthrax: What You Need To Know

Anthrax, for all the panic it's causing, has killed only one person and infected eight others. But exposure doesn't guarantee disease, and the illness is treatable. The basic facts:

What's the difference between being exposed to anthrax and being infected by it?

Being exposed means you came into contact with spores (that is, dormant bacteria with capsules around them). Spores can settle on your skin. They can reach your nasal passages through inhalation or if you touch an anthrax-laced finger to your nose. Being infected means the spores are multiplying in your body. The three types of anthrax exposure all come from the same bacterium (Bacillus anthracis), differing only in how they enter the body: in the cutaneous form, bacteria get in through a cut or an abrasion in the skin; in the inhalation form, spores are breathed in and reach the alveoli of the lungs; in the gastrointestinal form bacteria in contaminated meat reach the gut. "In monkey experiments, inhaling from 2,500 to 50,000 spores [not even enough to cover the point of a pin] kills half the animals," says molecular biologist Matthew Meselson of Harvard University.

Two days to six weeks later for inhalation, because spores can remain in the lungs for days or weeks before multiplying. The skin form shows up in one to several days.

Inhalation anthrax starts with a cough, fever, muscle aches, vomiting and fatigue, followed in a few days by breathing problems and sometimes meningitis and shock. Once respiratory distress kicks in, death usually follows within 36 hours. Cutaneous anthrax begins with a painless skin lesion that turns black, usually in three to six days.

A nasal swab picks up spores trapped in nose hairs. In the "quick test," antibodies bind to anthrax antigens on the spore surface. The gold standard is to let the spores germinate and form a characteristic gray colony, on which you perform a genetic test. A preliminary diagnosis takes 12 to 24 hours; a definitive one, twice that.

Antibiotics: ciprofloxacin (marketed as Cipro), amoxicillin (a form of penicillin) or doxycycline (a tetracycline). Victims of inhalation anthrax must take antibiotics for 60 days, starting immediately after exposure; if you wait until symptoms appear the spores have already germinated and begun to release toxins, in which case the mortality rate may approach 90 percent. For cutaneous anthrax, antibiotics can work even after a skin lesion turns black. With treatment, virtually all cutaneous patients survive. Even without it, some 70 percent do, says Dr. Michael Osterholm of the University of Minnesota.

Yes, if the spores get into a cut or if you inhale enough of the right size.

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