From the start, scientists have viewed the outbreak of tularemia on Martha's Vineyard as an ecological puzzle, never a case of bio-terrorism, despite tularemia's recognized status as a bacteria ideally suited for terrorism.

But the terrorist attacks of Sept. 11 and the anthrax cases that followed it have already left their mark on the investigation into how such a rare disease as tularemia could have struck 19 people on the Island in the last two years, one of them fatally.

For one thing, the anthrax panic of last fall instantly forced scientists from the federal Centers for Disease Control (CDC) out of the tularemia lab.

"Things got totally derailed with anthrax," said Dr. Katherine Feldman, an epidemic intelligence officer from the CDC's division of vector-borne infectious diseases in Fort Collins, Colo.

But the CDC is almost ready to close the books on the Vineyard tularemia investigation. "There are a lot of unanswered questions," said Dr. Feldman, "but the limiting factor in exploring those questions is budgetary."

Unless there are any new cases of tularemia, the last piece of work expected from the CDC will be the results of interviews conducted last summer with some 100 landscapers. Basically, the one firm conclusion reached by federal scientists was that people who mowed lawns or cut brush were at the highest risk for inhaling contaminated particles and contracting the pneumonic form of the disease.

But while the CDC prepares to bow out of the investigation, Dr. Sam Telford, a parasitologist from the Harvard School of Public Health whose team of researchers joined up with the CDC last summer, is not giving up. In fact, he's convinced that the climate of concern about bio-terrorism should compel an even deeper look into tularemia on the Vineyard and might even open up some funding opportunities.

"It's turned into something really interesting. We haven't the foggiest idea how people got tularemia," said Mr. Telford. "Maybe some inhaled it, but what did they inhale and where did it come from? Unless we know that, how on earth can we devise better methods for intervention?"

Mr. Telford is actively seeking grant money to support more intensive detective work. "I'm trying to capitalize on the bio-terrorism aspect," he said.

The fact is, tularemia is considered one of the top bio-terrorist agents, a long-lasting and highly infectious bacteria even in small amounts. According to Dr. Feldman's article in the Nov. 29 issue of the New England Journal of Medicine about the Vineyard outbreak in 2000, tularemia organisms can survive for several weeks in water, soil and decaying animal carcasses.

The pneumonic form of the disease can have a mortality rate as high as 60 per cent if left untreated, according to the article. The disease, also known as rabbit fever, is more commonly passed on by a tick bite from a dog tick, carrying the disease from infected animals to humans.

No place else in the country has ever experienced an outbreak of pneumonic tularemia. The Vineyard has seen two outbreaks, the other one in 1978 when 15 people were infected, seven of them exposed to the bacteria in one cottage in Chilmark.

While tularemia organisms are renowned for their longevity, no scientist can explain why the disease goes dormant for years at a time, only to resurface again in similar geographic areas of the Vineyard.

"Tularemia is what we call a very focal disease," said Mr. Telford. "It's not all over the Island. There are little hot spots here and there."

Katama in Edgartown and the Squibnocket area of Chilmark have already been identified as two hot spots, where several of the victims are thought to have been exposed. David Kurth, who died from tularemia in August 2000, had been mowing a lawn near Squibnocket about a week before he developed flulike symptoms and then failed to seek medical attention soon enough.

"The Martha's Vineyard situation has many, many unanswered questions, the most basic of which is to understand the ecology of tularemia on the Vineyard," said Dr. Feldman. "I don't think we've been able to scratch the surface on that. We just don't understand how climate contributes to an increased number of cases in a certain summer."

In 2000, public health officials confirmed 15 cases, 11 of them pneumonic. The next year, there were four more cases, three the pneumonic form. Even with the drop in numbers, scientists were alarmed to see the persistence of tularemia at that level since there are typically only one or two cases a year statewide, and sometimes none.

It's possible that public health precautions such as urging people to wear dust masks while mowing lawns and brush-cutting made a difference, but Dr. Feldman concedes there's no proof that the masks can block the inhalation of tularemia bacteria.

In her article in the medical journal, she points out that tularemia bacteria can measure as small as two-tenths of a micron in diameter, small enough to penetrate the masks, which block particles larger than three-tenths of a micron.

It's not hard to detect a sense of frustration from Dr. Feldman as the CDC nears the end of its investigation into tularemia on the Island. "There's a gold mine of things to figure out," she said.

But Mr. Telford is committed to keeping the investigation alive. "The Vineyard is a peculiar place with respect to tularemia," he said. "We need to get to the bottom of it. And we intend to get to the bottom."

But he could use some help, specifically from an Islander willing to host space for a freezer where the Harvard researchers could store dead rabbits, rats and other rodents known to be carriers of tularemia. A handful of animals trapped by scientists on the Island have tested positive for tularemia.

"We would actually buy a freezer," said the Harvard scientist. "We just need to find an upstanding citizen willing to host it and donate the juice to run it."