Sometime near the middle of an hour-long talk about a 25-year study of Lyme disease on Block Island, Peter Krause, M.D., mentioned a newer tick-borne disease called the Powassan virus. While that particular strain has not been detected on Block Island, Krause said the number of cases in the northeast is on the rise. He described Powassan as a deadly form of the virus.

In fact, a former U.S. Senator from North Carolina, Kay Hagan, died from the virus on Monday, Oct. 28. There are currently no treatments for Powassan, and Krause said scientists are tracking its migration. It is the type of virus, he said, that could travel to Block Island on a small animal. Krause said that the number of positive test results for Powassan “is on the rise” in the northeast.

It is for these and other reasons that Lyme disease is of such interest to islanders. Krause and a team of researchers have been studying ticks and Lyme disease on Block Island for the past 25 years, recording test results and discovering new aspects of the disease along the way.

Krause said that one of the most significant discoveries made during the past 25 years of the Block Island study was that individuals could experience co-infections, and that this was in fact not uncommon. This means a patient could test positive for both Lyme and babesiosis at the same time. “That was not known before and this was important,” he said.

He also said that it was discovered that infections in patients “commonly persist up to one year even after treatment” and despite the fact that patients are asymptomatic.

In light of that, someone in the audience asked Krause if someone that had been infected within the past year and had been treated should not give blood, Krause said “that was what the Red Cross is now recommending.”

A study of this length, and in such a controlled environment, is unusual, said Krause. He was also quick to say that the study could not have been undertaken without the willing help of so many Block Island residents. He called Block Island “the ideal site” and added “I appreciate what the island has contributed to this project. The residential population has been unbelievably cooperative.” The fact that the island has just one medical facility made tracking cases easier, said Krause. The doctor at the time the study started was Peter Brassard, M.D.

In his timeline of events surrounding ticks and Lyme disease, Krause referenced the introduction of six deer here in 1967 as the first significant event leading to where the island is now in terms of the disease.

Krause said that today there were between 600 and 1,000 deer on the island, despite efforts in recent years to reduce the herd. “The number of ticks explodes when there are deer present,” said Krause.He asked the audience if anyone had any recollection of Lyme disease on the island prior to 1967, but there was no response. There has not been an official deer count on the island for at least a couple of years, even though members of the Deer Task Force have been recommending a new count.

Krause said that deer reduction would be the most effective method for reducing Lyme disease “no matter how difficult it would be to reduce the deer by 90 percent,” Krause said. “You can’t reduce the herd by 10 percent. It doesn’t work.” He said he understood that some people were opposed to eliminating the deer.

There were other significant moments as the study got underway. In 1993, a Phase II Lyme disease vaccine began a trial run on Block Island. However, a class action lawsuit by plaintiffs claiming that the vaccine caused arthritis eventually led to the manufacturer taking it off the market. (Krause said it was later determined there was no causal link between the virus and arthritis.)

Krause cited some figures from early in the study. Between 1990 and 2000, there were 50 cases of babesiosis recorded on the island, and 75 cases of Lyme disease. It was discovered that 10 percent of the ticks were infected with babesiosis and 20 percent with Lyme on Block Island.

But what the past 25 years has taught is that what he called seroprevalence has increased in the past 25 years. (Seroprevalence is the number of persons in a population who test positive for a specific disease.) Krause also said the temperature of the island has increased, “and so has the humidity for the past 25 years. Generally, I think the disease is increasing and I think it’s weather related.”

He concluded by saying, “It’s really encouraging we’ve done all this, but it’s discouraging how much we don’t know.”