MICROBIAL RISK TOPICS

Overview
        In the past, the transmission of many infectious diseases was associated with drinking contaminated water. In the U.S. and other developed countries, the number of outbreaks has been vastly reduced through improvements in wastewater disposal practices, and through source (watershed) control and protection, and treatment of water supplies. Waterborne diseases, however, still exist, although the incidence of disease is small compared with the prevalence of diseases associated with other activities such as ingestion of contaminated food. Major outbreaks are generally associated with developing countries.

        In this section, microbial risks have been divided into three different families of microorganisms:

        Protozoan
        Bacteria
        Virus

The microbes may naturally be present in source water, or may be introduced through cross-contamination of wastewater. Some microbes may be found in biofilms within the distribution system.

        The following section discusses the issues related to microbial risks such as regrowth potential in distribution systems and waterborne disease prevalence. Factsheets providing general information, prevention, and treatment guidelines for seventeen waterborne diseases are also included.

Table 1. Diseases or Disease Agents Associated with Various Activities

Food or Water Contamination: Giardia, Cryptosporidium, Shigella, Salmonella, Hepatitis A, E. Coli, Campylobacter, Clostridium, Listeria, Norwalk virus, Streptococcus, Staphylococcus, Vibrio species.

Table 2. Incidence Rates for Some Common Waterborne Diseases

DISEASES DISEASE RATES (PER ANNUM)
Salmonellosis 137
Shigellosis 447
Campylobacteriosis 228
Hepatitis A 36
Gastroenteritis 11872

[Data averaged over a 24-year period (1971-1994). CDC (Centers for Disease Control). 1984. Water-Related Disease Outbreaks. Annual Summary 1983. Centers for Disease Control, Public Health Service, U.S. Department of Health and Human Services, Atlanta, GA pp 19.]

Biofilms
Parasites
Bacteria
Viruses




Source: http://www.ci.sf.ca.us/puc/wqfs/outbreak.htm