Maryland officials are convinced that the outbreak of pneumonia cases suspected of being Legionnaire's disease in Charles County is tailing off, according to Dr. Feng-Ying C. Lin, the state epidemiologist.

Fifty-five cases of pneumonia have been reported in southern Maryland in the past five weeks, and state health officials suspect that many of the victims may be suffering from Legionnaire's disease.

Only one case of Legionnaire's disease has been confirmed, in a woman who died last month after appearing to have contracted pneumonia. The disease is suspected in another woman's death.

A house-to-house survey of patients with the suspect pneumonia has not turned up the source of the disease, officials said. State officials have asked for assistance from the Centers for Disease Control, which is expected to provide one or more experts in environmental microbiology, Lin said.

The disease usually is transmitted from a single environmental source in the form of bacteria-bearing water droplets inhaled by the victims. It is not contagious.

All but one of the pneumonia patients have been residents of Charles County. The sole exception is a woman who lives just over the Charles County border in Prince George's County, Lin said.