Estimating the infection risk in recreational waters from the faecal indicator concentration and from the ratio between pathogens and indicators

In the past, a series of epidemiological studies have been conducted with t he aim of establishing a relationship between the concentration of faecal i ndicators and the number of bathing related illnesses. The final goal was t o find a level of faecal indicators which could be considered acceptable un der the point of view of the risk of infection. Because epidemiological stu dies are costly, additional means of obtaining health-related standards are desirable, which are easier to carry out and more affordable than epidemio logical studies. In this paper. we have made an attempt to develop such an alternative. Setting out from published data on the dose response relations hip for rotaviruses in humans, and from the lognormal distribution of faeca l indicators assumed to exist in surface waters, we have established a seri es of equations which link the concentration of faecal indicators with the risk of infection. (C) 2000 Elsevier Science Ltd. All rights reserved.