THURSDAY, March 7, 2002 (HealthDayNews) -- The stampede for antibiotics in last fall's bioterrorism attack, which catapulted an obscure drug called Cipro into the American lexicon, appears to have been more than an exercise in mass panic.
A new study suggests the deadly outbreak of lung anthrax would have been much worse had people not taken the drugs.
A new statistical formula, which appears in tomorrow's issue of Science, predicts that as many as nine cases of inhalation anthrax were prevented by prescribing Cipro and other antibiotics to people potentially exposed to the bacteria. Anthrax was confirmed or suspected in 22 people. Eleven cases involved the skin form of the infection, while 11 -- including five deaths -- were the much more lethal inhaled form.
Some 32,000 Americans potentially exposed to anthrax began taking antibiotics as a precaution against infection, according to the Centers for Disease Control and Prevention.
Many worked at the Florida media company where the first anthrax case -- and the first death -- occurred, and at postal facilities in New Jersey and Washington, D.C., where germ-tainted mail was processed.
While fewer than two dozen people developed anthrax infections in the outbreak, it's likely that more would have fallen ill without the drugs. How many is, of course, speculation. However, an educated guess is possible.
"By looking at the number of cases and the interval between exposure and the use of antibiotics, and using what we know about the incubation interval, we can look forward to see how many case might have occurred," says Ron Brookmeyer, a Johns Hopkins University biostatistician and lead author of the new study.
He and a graduate student, Natalie Blades, analyzed the three largest clusters of possible anthrax exposures: those in Florida, New Jersey and Washington, D.C. They also considered a 1979 anthrax outbreak at a Soviet bioweapons facility in Sverdlovsk.
The researchers did not include the deaths of two women in New York and Connecticut, the source of whose infections haven't been determined. Nor did they analyze cases of skin, or cutaneous, anthrax in New York City.
Incubation periods for anthrax vary with a person's age, the number of bacteria spores they inhale, and whether they have conditions that make them more susceptible to infection.
"The incubation period plays a very crucial role in how epidemics unfold," said Brookmeyer, whose earlier work helped model the pattern of the AIDS epidemic.
The researchers found that while the number of people who may have inhaled ample spores to become sick varied widely, the most likely figure was 17.
"Our calculations show that the outbreak would have been about twice as large" as it was had antibiotics not been recommended widely, Brookmeyer says.
"Our response in initiating the public health measures did prevent disease, did potentially save lives," adds Brookmeyer. The study also underscores the importance of rapid surveillance in case of an outbreak, and the quick recognition of first cases of infection.
Brookmeyer says the findings should be encouraging for people who took their 60-day course of antibiotics to prevent anthrax.
"We think few, if any, would be at risk of subsequent disease" after stopping, he says. "We can't say it's zero, but we think it's less than 1 percent."
Although 10,000 people had been encouraged to take a 60-day preventive course of antibiotics, it's not clear how many stayed on that regimen that long.
The new study should burnish the image of CDC director Dr. Jeffrey Koplan, who has been criticized for his handling of the anthrax attack.
Dr. Jim Hughes, director of the National Center for Infectious
Diseases, a division of the CDC, said the Science paper demonstrates the agency's
reaction was sound. "We feel the public health response certainly resulted in
the prevention of some additional cases of illness that almost certainly
would have occurred," Hughes said. Recommending preventive antibiotics "was
the right thing to do."
Dr. Alina Alonso, an official at the Palm Beach County Health Department, which helped control the Florida anthrax cases, says her agency was gratified by the study. "We certainly feel here in South Florida that lives were saved as a result of the massive prophylaxis that was conducted," Alonso says.
Despite reports of some side effects and fears that overuse of powerful antibiotics would promote drug-resistant germs, "we feel strongly that whether we saved nine [lives] or just one, certainly in this situation it would have been definitely worth it," she says.
What To Do: To learn more about anthrax and other bioterror agents, visit the CDC. For more on the Soviet outbreak of anthrax, try this site at George Washington University.
