hygiene experts that viruses may be more resistant to chlorine treatment than
bacterial disease agents.
There were 142 outbreaks of waterborne diseases—gastroenteris and diarrheal disease—affecting 18,000 people reported between 1946 and 1960 [45].
These cases were believed to be by viruses; bacteria are not often found to be
the causative agent.
A small number of polio outbreaks can possibly be attributed to con—
taminated water supply systems. In November of 1958, for example, an outbreak of polio occurred in Edmonton in the province of Alberta, Canada.
Cases were uniformly distributed throughout the city and no common sources
of food, milk, or public contact could be established; an additional factor ruling out personal contact was that the cases occurred too closely together to
allow enough time for the incubation period. Cases of polio had occurred in
Devon, a town upstream from Edmonton, earlier in the season. At this time,
the chlorination of Devon’s sewage effluent had been inconsistent and polio
viruses could have been carried to the Edmonton water treatment
Al—
though the Edmonton plant then settled, softened, ltered, and chlorinated
the water, this was thought to be the most likely route for the polio virus to
have taken [46].
More recently, a polio-like virus was found in drinking water which had
been tested as safe. According to a report by two researchers at the University
of Michigan and a health ofcial from the Michigan Department of Health,
this was the rst time a virus had been isolated from drinking water [47]. On
]anuary 18 and 20 of 1970, complaints of intestinal illness, with symptoms including nausea, vomiting, and diarrhea, were made to Michigan health offi—
cials. Since all of the people affected had eaten at the same restaurant, health
ofcials tested the food there, but no bacteria that could have caused in—
testinal disturbance were uncovered.
Subsequently, water samples were tested. The restaurant drew water from
a 100—f00t well on the edge of a draineld which received waste water; thus
the well could easily have become contaminated. Using routine procedures
for bacteriological testing, no Escherichia coli, Salmonella, or Shigella were
found. The examiners then concentrated the water samples, making the
chances of detecting bacteria more likely. When this was done, both bacteria
and a polio—type virus were recovered. Since no attempt was made to isolate
the virus from the patients, there is no direct proof that it actually caused the
intestinal illness. However, the study does show that viruses can remain alive
in water and that routine bacteriological surveys may not be adequate pro—
tection against disease.
A Lack of Knowledge. Questions concerning the adequacy of PHS bac—
teriological standards and the treatment processes designed to safeguard them
were raised at hearings on “Safe Drinking Water” held in May 1971 by the
Subcommittee on Public Health and Environment of the Committee on In—
terstate and Foreign Commerce of the House of Representatives [48]. The
.
Biological Hazards 165
bacterial disease agents.
There were 142 outbreaks of waterborne diseases—gastroenteris and diarrheal disease—affecting 18,000 people reported between 1946 and 1960 [45].
These cases were believed to be by viruses; bacteria are not often found to be
the causative agent.
A small number of polio outbreaks can possibly be attributed to con—
taminated water supply systems. In November of 1958, for example, an outbreak of polio occurred in Edmonton in the province of Alberta, Canada.
Cases were uniformly distributed throughout the city and no common sources
of food, milk, or public contact could be established; an additional factor ruling out personal contact was that the cases occurred too closely together to
allow enough time for the incubation period. Cases of polio had occurred in
Devon, a town upstream from Edmonton, earlier in the season. At this time,
the chlorination of Devon’s sewage effluent had been inconsistent and polio
viruses could have been carried to the Edmonton water treatment
Al—
though the Edmonton plant then settled, softened, ltered, and chlorinated
the water, this was thought to be the most likely route for the polio virus to
have taken [46].
More recently, a polio-like virus was found in drinking water which had
been tested as safe. According to a report by two researchers at the University
of Michigan and a health ofcial from the Michigan Department of Health,
this was the rst time a virus had been isolated from drinking water [47]. On
]anuary 18 and 20 of 1970, complaints of intestinal illness, with symptoms including nausea, vomiting, and diarrhea, were made to Michigan health offi—
cials. Since all of the people affected had eaten at the same restaurant, health
ofcials tested the food there, but no bacteria that could have caused in—
testinal disturbance were uncovered.
Subsequently, water samples were tested. The restaurant drew water from
a 100—f00t well on the edge of a draineld which received waste water; thus
the well could easily have become contaminated. Using routine procedures
for bacteriological testing, no Escherichia coli, Salmonella, or Shigella were
found. The examiners then concentrated the water samples, making the
chances of detecting bacteria more likely. When this was done, both bacteria
and a polio—type virus were recovered. Since no attempt was made to isolate
the virus from the patients, there is no direct proof that it actually caused the
intestinal illness. However, the study does show that viruses can remain alive
in water and that routine bacteriological surveys may not be adequate pro—
tection against disease.
A Lack of Knowledge. Questions concerning the adequacy of PHS bac—
teriological standards and the treatment processes designed to safeguard them
were raised at hearings on “Safe Drinking Water” held in May 1971 by the
Subcommittee on Public Health and Environment of the Committee on In—
terstate and Foreign Commerce of the House of Representatives [48]. The
.
Biological Hazards 165