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Last Updated

30 Oct 2002

Source: Washington Post, May 14, 2002.

Study: Anthrax Tainted Up to 5,000 Letters

Cross-Contamination Blamed For Deaths of 2 Women

By Guy Gugliotta, Washington Post Staff Writer

Envelopes full of anthrax spores cross-contaminated as many as 5,000 letters in the eastern United States, almost certainly causing the mysterious deaths of two women in New York City (case 22) and rural Connecticut (case 23), scientists said yesterday.

A mathematical model describing last fall's attacks suggested that focusing only on anthrax-laden envelopes could be a grave mistake: "The original letters were extremely dangerous," said Vanderbilt University mathematician Glenn Webb. "But there was also great danger from cross-contamination."

Webb and co-researcher Martin Blaser, chairman of medicine at the New York University Medical School, said the model could be used to predict the course of future letter-borne anthrax attacks and perhaps save lives. Their research was published today in the Proceedings of the National Academy of Sciences.

"We hope there won't be any further outbreaks," Blaser said. "But if there were, this could help us identify the populations at risk and might help us move more quickly to find the source of the initial exposures."

Anthrax attacks in the United States resulted in 18 confirmed cases of the disease and five deaths. One fatality may have been the direct recipient of an anthrax letter (case 5), and two others were postal workers who handled tainted letters at the District's Brentwood facility (cases 15 and 16).

But the last two, health worker Kathy T. Nguyen, 61 (case 22), who lived in a Bronx apartment, and Ottilie Lundgren, 94 (case 23), from rural Oxford, Conn., appeared to have had no direct contact with anthrax-infected mail.

"What was particularly disturbing was the woman in the Bronx, because there was no clear way in which she got the anthrax," said Blaser, who at the time was serving on a biological threats task force convened by then-New York Mayor Rudolph W. Giuliani. "But as soon as the Connecticut case came up, I had a pretty good hypothesis about what was going on -- cross-contamination carrying a low dose of the microbe."

He contacted Webb, with whom he had worked previously, and Webb developed a model based on "nodes" of exposure, which included mailboxes, entry post offices, regional sorting centers, destination post offices and final destinations.

Working only from published accounts of the anthrax attacks, Webb estimated that the original letters probably contained one trillion spores, and as they made their way through the system, they contaminated others, which contaminated still others. Webb assigned spore values to each node, estimating that the Nguyen and Lundgren letters probably held between 10 to 100 spores when the victims received them. Webb said he adjusted the model to reflect lessons learned during the outbreak: that antibiotics can both prevent people from catching the disease and save those who have it; that older people are more susceptible, and that death can occur from exposure to very few spores. Blaser said Lundgren probably caught anthrax from "second generation" cross-contamination caused by her mail's exposure to an anthrax-tainted letter in a nearby town.