The anthrax spores that infected a New Hampshire woman are the same strain as spores found on an electrical outlet and two drums used at a gathering she attended in early December, medical investigators said.
Test results received Thursday from the Centers for Disease Control and Prevention confirmed the match between the patient's strain and the contaminated items at the United Campus Ministry Center in Durham.
The results bolster the theory that the woman swallowed anthrax spores propelled into the air during a Dec. 4 drum circle at the center, said Dr. Elizabeth Talbot, adviser to the state Department of Health and Human Services.
The woman, who is in critical condition in a Boston hospital, has an extremely rare form of anthrax involving the gastrointestinal system. Two recent U.S. anthrax cases involved drums covered with animal hides, but those involved spores that were inhaled into the lungs or entered through the skin.
Health officials shut down the ministry building earlier this week and offered antibiotics and vaccines to about 80 people _ 60 who attended the drum circle, University of New Hampshire students who lived in the building and those who worked there.
Talbot said health officials have identified about half of those eligible for the treatments but emphasized it would be up to each individual to decide whether to take the 60-day course of antibiotics or get the three vaccination injections.
Anthrax is a potentially fatal disease caused by bacteria. Infection from natural sources is rare in developed countries, but occurs regularly in poor nations. It is not transmitted from person-to-person. The gastrointestinal form usually occurs after eating raw or undercooked contaminated meat and is fatal in 25 to 60 percent of cases, according to the CDC.
In 2001, letters containing anthrax spores were mailed to journalists and two U.S. senators in the weeks following the Sept. 11 terrorist attacks. At least four people, including two postal workers and a photo editor, died from exposure to the letters and more than a dozen others became ill.
Unlike with weapons-grade anthrax, Talbot said not much is known about the natural form of anthrax, including how it is transmitted in the environment or how much a person must be exposed to in order to get sick.
"We know anthrax is part of our natural environment. It's possible there are spores on any one of our clothes as we speak," she said. "It's a paradox to me that as common as these are, it is very, very unusual to have disease."
There were a total of 66 drums at the Dec. 4 event, Talbot said. Test results on most of the others are expected to be released Saturday, and officials were asking those who brought their own drums to the circle to consider having them tested.