Six cases of tularemia this spring and summer on Martha's Vineyard have been confirmed by the state Department of Public Health.

All six individuals who contracted the disease, who ranged in age from 33 to 67, either were landscaping or were outside near where landscaping was occurring. They contracted the potentially fatal disease by breathing in the Francisella tularemia bacterium between May 13 and July 5, health officials said.

All have been successfully treated with antibiotics for the disease, and are recovering.

For unknown reasons, Martha's Vineyard over the past seven years has been a hotspot for tularemia in Massachusetts, a state where the disease is otherwise rare.

Before the current outbreak began on the Vineyard with 15 cases in 2000, one of them fatal, the state had been seeing about three cases a year. Last year, according to Dr. Bela Matyas, medical director of the Department of Public Health epidemeology program, 14 cases were reported in Massachusetts, all on the Vineyard.

Of the six cases reported so far this year on the Vineyard, Dr. Matyas said, four were professional landscapers, the fifth was a retiree who did his own landscaping and the sixth was a construction worker who was outside near where landscaping was taking place.

To Dr. Matyas, the last case is an indication of how virulent the airborne form of the disease can be. Very few airborne particles, he said, are needed to introduce the disease into an individual.

Typical symptoms of the airborne form of Tularemia include fever and coughing, tightness in the chest and shortness of breath. If the disease is left untreated, death can result.

The speed with which pneumonic tularemia can overtake an individual can vary based on health; people who are in good health with strong immune systems typically fare better than people who are weak or in poor health.

But strength and health provide no immunity against the disease. Most of the infected Vineyard individuals have been strapping young landscapers, Dr. Matyas said.

The health department has sent out fact sheets and a public health update to all landscaping companies on the Vineyard as well as to physicians on the Cape and Islands.

Tularemia infection can also come through tick bites, scratches or breaks in the skin and consumption of undercooked wild animals. Of the 14 individuals infected on the Vineyard last year, Dr. Matyas said, two contracted the disease through the skin and one had ingested the bacterium.

Tularemia commonly infects small wild animals, especially rabbits (hence the disease's nickname, rabbit fever). The state suspects that the landscaping, by stirring up carcasses or fecal matter in the ground, unleashes the bacterium, sending it into the air and down the lungs of nearby humans.

According to the health department, tularemia is not spread from person to person, though a few people have gotten sick after bites from infected pet cats.

Dr. Matyas said physicians and nurses on the Vineyard are alert to tularemia, and have been diagnosing the disease while the symptoms still were mild.

One concern at the state agency is that health care providers off-Island might be less aware of tularemia's symptoms. That could give the disease a head start in people who visit the Island for business or pleasure, subsequently returning to their mainland home where the disease is rare.

Yesterday, the health department recommended that people on Martha's Vineyard seek medical attention immediately if they develop fever or respiratory symptoms within seven days of breathing in dust, soil or grasses while landscaping. The department said people also should seek medical attention if they develop skin sores, swollen lymph glands or a rash after a tick bite.

To reduce the risk of infection, the health department said, individuals involved in any landscaping activities, including lawn mowing, on the Vineyard should carefully clear areas of dead animal bodies before using lawn mowing or brush cutting equipment.

The department suggests that people use an appropriate respirator or mask for further protection.

Additional precautions listed by the state that people can take to reduce their risk from tularemia include:

* Avoiding contact with wild animals, their droppings or dead bodies.

* Decreasing rodent populations near homes by raising woodpiles off the ground, fencing off garden areas, and keeping garbage in rodent-proof containers.

* Using gloves, an appropriate respirator and eye protection when skinning or dressing wild animals, and cooking any wild game completely before eating it.

* Avoiding drinking water that may have been contaminated by wild animals and preventing animal access to wells.

* Avoiding areas where ticks are likely to be, using repellents on people and pets, and doing a daily tick check.

More information about tularemia is available on the state Department of Public Health web site at Individuals who have questions regarding tularemia also can get in touch with their town board of health, or the state Department of Public Health's division of epidemiology and immunization at 617-983-6800.

The disease so far this year has infected male and female individuals on the Vineyard, according to Donna Enos, the infectious control nurse since 1998 at the Martha's Vineyard Hospital.

Ms. Enos said the hospital is stressing prevention, especially that people wear masks while they're landscaping.

She said the masks, which are available at hardware stores, should carry a rating of N-95 or higher. She also said the masks should cover the nose as well as the mouth.

Ms. Enos said she's aware that the masks are difficult to wear in the hot weather, and that they don't always effectively cover the facial area when the individuals have mustaches or beards. But she said any steps to minimize exposure to the airborne bacterium are worth taking.

She urged people who start experiencing shortness of breath, coughing, or flu-like symptoms this summer to get checked out by health care providers. Ms. Enos said they'll receive treatment for the disease just in case, even if subsequent tests reveal the sickness wasn't tularemia.

"You'd rather be safe than sorry," she said.