THE QUEENSLAND CHOLERA INCIDENT OF 1977 .2. THE EPIDEMIOLOGICAL INVESTIGATION

Abstract

In 1977 the 1st case of cholera known to be contracted in Australia during the 7th pandemic occured 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 residence and a stretch of neighboring river than 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. The persistence of the microorganism in the 1st river over a 2 mo. period, despite increases in river flow following significant rainfall, shows that the cholera vibrio can survive for a long period and can 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, it is important to provide bacteriologically safer water supplies and, possibly, to expand the definition of a cholera-receptor area.