Legionella infections in Scotland.

Four thousand two hundred and thirty-five sera from 2794 patients and 740 sera from 735 tourists domiciled in Scotland recently returned from abroad were examined between 1977 and 1981 for antibodies to Legionella pneumophila and related organisms. In addition, specimens were examined from some patients for cultural or serological demonstration of these organisms in lung or sputum. One hundred and ten cases were diagnosed, 104 serologically, five by immunofluorescence demonstration of legionellas in lung biopsy or autopsy specimens and L. pneumophila serogroup 1 was isolated from a further case. Of patients with pneumonia 6.7% showed evidence of legionella infection. Only 0.4% of healthy tourists had antibodies at a level of greater than or equal to 256. The majority of cases occurred in patients aged 50-69 and in 36 patients the infection was acquired outside the United Kingdom. Males predominated, the male: female ratio being 2: 1. Cases were less frequent in the first quarter of the year but those originating in Scotland were equally common in the remaining three quarters. Cases with disease acquired abroad added to indigenous cases resulted in a summer peak occurring in July, August and September. There were no outbreaks of legionellosis in Scotland.