Legionnaires' disease in Vermont, May to October 1977.

Thirty-two confirmed and 24 highly probable cases of Legionnaires' disease occurred in Vermont between May 1 and Oct 15, 1977. Confirmed cases had positive results for direct fluorescent antibody testing of lung tissue or fourfold rise in antibody titer. Highly probable cases had one elevated titer (greater than or equal to 1:256) and a compatible illness. Forty-eight (86%) had underlying chronic disease, and 22 (39%) were immunocompromised. Prominent early symptoms were fever, cough, chills, and malaise. All but one patient had verified pneumonia. Courses ranged from a pneumonia not requiring hospitalization to respiratory failure necessitating support with mechanical ventilation. Seventeen patients died. Although the clinical presentation was variable, rapid development of high fever and leukocytosis together with negative cultures of lower respiratory tract secretions strongly suggested the diagnosis in an epidemic setting.