(Reuters) - Legionnaires' disease, a strain of pneumonia, is on the rise in New England this year, and the reason for the flare-up remains unexplained, health officials said on Tuesday.
Total cases confirmed in Maine, Massachusetts and Connecticut have nearly doubled from last year while many other northeastern states were also showing sharp increases. States in other parts of the country were not.
Maine's Center for Disease Control and Prevention issued an advisory on Monday to all state health care providers to watch for and report Legionnaires' cases after it documented 18 cases so far this year, up from 11 in all of 2010.
"This is a spike, and we need to be looking into this and we need to alert people," Maine's state epidemiologist, Dr. Stephen Sears, told Reuters.
Legionnaires' disease is caused by inhaling an infectious dose of Legionella bacteria, usually found in contaminated water in sources such as cooling towers, whirlpool spas, showers and faucets.
The illness, named for a 1976 outbreak at an American Legion convention in Philadelphia, causes pneumonia and kills 5 to 30 percent of patients, with 8,000 to 18,000 people hospitalized each year.
Symptoms can include high fever, chills, chest pain, a cough, and often headaches and muscle aches. It can be treated with antibiotics.
Hard-hit Massachusetts confirmed 211 Legionnaires' disease cases as of November 23, up from 118 cases in all of 2010, while Connecticut saw 72 cases, versus just 47 last year, said Jeff Dimond, a CDC spokesman in Atlanta.
In the Mid-Atlantic, populous New York State reported 526 cases this year compared to 379 last year, and Pennsylvania saw 450 cases, up from 299 last year, the CDC said. By contrast, California, with its 200 cases this year, has a mere 10 more than it counted during 2010.
Maine epidemiologist Sears has spoken with his Massachusetts and Connecticut counterparts about the jump in scattered individual cases this fall in New England, but they have not yet managed to pinpoint a specific reason for it.
Experts were considering possibilities such as an increased awareness of Legionnaires that has led to more testing, changes in climate, more air conditioner usage and an increase in the number of seniors, who are more susceptible to infection.
"We have looked but we haven't found common connections at this point," Sears said. "We've found nothing that tied the people together epidemiologically."
The Canadian province of Quebec has issued a similar advisory after a rise in cases there, Sears said.
(Reporting by Zach Howard. Editing by Barbara Goldberg and Cynthia Johnston)