The Queensland cholera incident of 1977. 2. The epidemiological investigation.

In 1977 the first case of cholera known to be contracted in Australia during the seventh pandemic occurred in southeastern Queensland. Toxigenic isolates of Vibrio cholerae, biotype eltor, serotype Inaba, phage-type 2, were obtained from the index case, a companion of the patient, the reticulated water supply of their place of residence, and a stretch of the neighbouring river that was being used to supplement fully treated water piped from Brisbane. Treatment of the auxiliary supply consisted solely of chlorination. A section of another river was later shown to contain V. cholerae. No source of pollution was identified for either river. From the persistence of the microorganism in the first river over a two-month period, despite increases in river flow following significant rainfall, it seems that the cholera vibrio can not only survive for a long period but can also grow in the river water. This strongly suggests that certain surface, and possibly subsurface, waters may serve as potential silent foci of V. cholerae. Hence the importance of providing bacteriologically safe water supplies, and the possible need to expand the definition of a 'cholera-receptive area'.