Without prophylactic antibiotics, anthrax cases among three groups might have doubled

Mar 11, 2002 (CIDRAP News) – More than twice as many cases of inhalational anthrax could have occurred at Postal Service facilities and a Florida media company last fall if workers had not been given prophylactic antibiotics after the disease struck at those sites, according to a statistical analysis published in the Mar 8 issue of Science.

A total of eight cases of inhalational anthrax occurred at postal facilities in New Jersey and Washington, DC, and at American Media Inc. If prophylactic antibiotics had not been given to about 5,000 people at those sites, another nine cases could have occurred, according to the analysis by Ron Brookmeyer and Natalie Blades of the Johns Hopkins Bloomberg School of Public Health in Baltimore.

"The epidemic in these three groups could have been about twice as large had they not undergone a timely regimen of antimicrobial therapy," their report states. Nationwide, a total of about 10,000 people were advised to take antibiotics for 60 days because of possible anthrax exposure last fall.

The Science report focused on the two cases of inhalational anthrax at American Media, two among postal workers in New Jersey, and four among postal workers in Washington, DC. The authors based their estimate on the dates of anthrax exposure, symptom onset, and start of antibiotic treatment, along with the estimated incubation period for the disease. The postal workers' exposures were linked to letters sent to US senators, but the source and date of exposure for the Florida cases remain unknown, so the authors had to estimate the date for that site.

Brookmeyer and Blades estimated the incubation period for inhalational anthrax at 11 days, which was the median period in the 1979 outbreak in Sverdlovsk, Russia. The estimated number of cases that would have occurred without prophylactic antibiotics increased with longer assumed incubation periods; with an incubation period of 15 days, the estimated number of cases was 26, the report says.

A total of 18 people contracted anthrax last fall, and five died. The five deaths included two postal workers in Washington, DC, a photo editor at American Media, a hospital worker in New York City, and an elderly woman in Connecticut.

Brookmeyer R, Blades N. Prevention of inhalational anthrax in the U.S. outbreak

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