Seven people have contracted Legionnaires' disease (search) this summer in Rapid City, state Health Department officials said Friday. One person has died.

The first case came the week before Memorial Day but was not identified as Legionnaires' until later in the summer when health officials received other reports of the disease, said Lon Kightlinger, the state's epidemiologist.

The Health Department has beefed up surveillance for the disease in the wake of the Rapid City (search) outbreak but no new cases have been reported since July 7, he said.

A source for the infection has not been identified and investigators have found few connections among those who got the disease, said Kightlinger.

"That's what's been so frustrating about it." he said. "There has been no apparent link."

Kightlinger declined to identify the person who died or give other specifics about the person's age or gender. The death occurred July 1.

He said the median age for the seven cases was 62 and that no one younger than 55 had contracted the illness.

Usually, South Dakota has a couple of cases of Legionnaires' disease each year, Kightlinger said. In 2004, five cases were reported and two cases were reported the year before. No one died.

So far, the Rapid City cases are the only ones to have been reported in South Dakota this year, said Barb Buhler, a spokeswoman for the Health Department.

Legionnaires' disease, which gets its name from an outbreak at an American Legion convention in 1976, is caused by the Legionellosis bacteria. It can cause fever, muscle aches and pneumonia.

Most people exposed to the bacteria never get sick. But older people and those with weak immune systems are at increased risk of developing the disease. Legionnaires' is treatable with antibiotics.

People shouldn't be concerned that the Rapid City area is at higher risk for the disease, said Kightlinger.

"We don't want people to worry," he said. "I'd downplay any fear that people might have of this."