The waterborne diseases include viruses, bacteria and protozoa. BACTERIAL
diseases are common to most countries; differences tend to be in the form of additional
types of bacteria and a higher incidence in wastewaters in developing or tropical
countries. Those bacteria sufficiently prevalent to be of concern in developed nations are
Samonella, enterpathogenic Escherichia coli, Shigella, and Yersinia; and to a lesser
extent Legionella and Leptospira. Samonella and E. coli are always found in sewage and
sludge. Salmonella is present in domestic animals; only Salmonella typhi (typhoid) lives
in man only. Shigellae (dysentery) is essentially exclusively a human disease. Vibrio
cholerae (cholera) survives in water for only a short time; epidemics associated with
contaminated drinking water show recent contamination. Shigellosis is the second most
common enteric bacterial infection observed in the U.S.A. In 1976, the incidence rate for
shigellosis was 6 per 100,000; salmonellosis at 11 per 100,000.
LEGIONELLA has been isolated from the water in the cooling towers of air
conditioning units in association with disease outbreaks, suggesting that disease in man
results from exposure to aerosols containing the organism. Wastewater-exposed workers
and the neighbors of treatment plants have not shown that exposure posed a risk of
SALMONELLA: The Cincinnati-Chicago-Memphis study showed higher levels
in wastewater workers; especially among inexperienced workers in Memphis.
YERSINIA: A study of sewage workers in Manitoba did not reveal a wastewaterexposure effect.
BACTERIAL ENDOTOXINS: Toxins released from the cell walls of gramnegative bacteria after their death can produce fever and chesttightness in exposed
individuals. This appears to be a problem during sludge heat-treatment operations for
sludge drying, at land application sites, and at composting operations. Individuals
exposed to composted sludge in Philadelphia and Washington, D.C., showed higher
antibody levels to compost -deri ved endotoxin.
HEPATITIS: Hepatitis A requires serological (antibody) analysis since most
infections are subclinical and are not manifested as overt disease. Hepatitis B is a major
unconquered disease: some 200 million people are chronic carriers of the virus and a
significantly minority of these go on to develop cirrhosis or cancer of the liver. There are
reliable diagnostic procedures and a vaccine. Hepatitis B is transmitted via blood or
bloodcontaminated materials; blood from skin and wounds or sores; tattooing
acupuncture, or ear piercing without rigorous sterilization of equipment. Recent evidence
indicates that sexual transmission is possible; semen and other genital secretions can
transmit the virus; and saliva also contains the virus. There are strict disposal procedures
for contaminated materials.
AIDS: The Aids virus does not appear to survive outside the body. For infection
to occur, considerable numbers of viruses must be involved. For example, of 1100
hospital workers who have experienced needle punctures with AIDS-contaminated
materials, only 2 have developed antibodies and these involved deep intramuscular
puncture wounds. For AIDS to be transmitted via sewage would involve blood in the
urine or feces of the infected individual to be discharged in the sewer. Infection would
have to involve contact of this material with cuts or broken skin. The AIDS virus may
live for an hour in blood specimens kept at room temperatures which are close to body
temperatures; otherwise, the virus seems to die off at cooler temperatures. This would
seem to mean a low chance of survival in the sewer system. As with hepatitis B, there are
strict disposal procedures for contaminated materials.
NORWALK VIRUS is largely associated with epidemics of gastroenteritis in
older children or adults. Infections are infrequent «5%) in children under 10 years; 50 60% of adults have serological evidence of infections.
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