Perinatal listeriosis: report of an outbreak.

From April to August, 1981, 15 cases of perinatal listeriosis were seen in Halifax, Nova Scotia, Canada. Nine of the 15 mothers presented with 'flu-like' symptoms, 3 had symptoms of an upper respiratory infection and 2 a history of fever alone. During labor 11 mothers had fevers greater than 38 degrees C and 9 had stained amniotic fluid. Twelve delivered prematurely. Among the 15 infants the most common clinical features were perinatal depression, respiratory distress, fever, hematologic abnormalities and rash. There were 7 deaths (case fatality rate of 46.7%). A transplacental route of infection for the fetus was suggested by the signs of systemic illness in most mothers, the lack of positive maternal vaginal cultures and evidence of chorioamnionitis, premature labor, severe fetal disease and intrauterine death prior to membrane rupture. The delivery of healthy infants to two mothers who had received antepartum treatment for listeriosis suggests that earlier recognition and treatment of maternal disease will improve perinatal outcome.