Risk of Disease Rises With Water Temperatures

[Medical Alliance]

Risk of Disease Rises With Water Temperatures

By Kari Lydersen
Washington Post Staff Writer
Monday, October 20, 2008; A08


When a 1991 cholera outbreak that killed thousands in Peru was traced
to plankton blooms fueled by warmer-than-usual coastal waters, linking
disease outbreaks to epidemics was a new idea.

Now, scientists say, it is a near-certainty that global warming will
drive significant increases in waterborne diseases around the world.

Rainfalls will be heavier, triggering sewage overflows, contaminating
drinking water and endangering beachgoers. Higher lake and ocean
temperatures will cause bacteria, parasites and algal blooms to
flourish. Warmer weather and heavier rains also will mean more
mosquitoes, which can carry the West Nile virus, malaria and dengue
fever. Fresh produce and shellfish are more likely to become
contaminated.

Heavier rainfalls are one of the most agreed-upon effects of climate
change. The frequency of intense rainfalls has increased notably in
the Midwest, the Northeast and Alaska, and the trend will accelerate,
said the 2007 report of the United Nations' Intergovernmental Panel on
Climate Change.

The consequences will be particularly severe in the 950 U.S. cities
and towns -- including New York, the District, Milwaukee and
Philadelphia -- that have "combined sewer systems," archaic designs
that carry storm water and sewage in the same pipes. During heavy
rains, the systems often cannot handle the volume, and raw sewage
spills into lakes or waterways, including drinking-water supplies.

On Sept. 13, during an unrelenting downpour, Chicago chose to prevent
urban flooding by opening and releasing runoff containing raw sewage
into Lake Michigan. About a month later, a University of Wisconsin
study published in the American Journal of Preventive Medicine
predicted an increase of 50 to 120 percent in such releases into the
lake by the end of the century.

"One of the strongest indicators from climate models is more intense
rains," said co-author Stephen Vavrus, director of the university's
Center for Climatic Research. "They don't agree on everything, but
they do agree on that. A warmer atmosphere holds more moisture, so as
we get more moisture in the air, when we do have a storm situation,
you get more total rainfall."

From 1948 to 1994, heavy rainfall was correlated with more than half
of the nation's outbreaks of waterborne illness, according to a 1991
study commissioned by the Environmental Protection Agency. In one of
the worst, torrential rains in Milwaukee in 1993 triggered a sewage
release that exposed 403,000 people to cryptosporidium, a protozoan
parasite transmitted in fecal matter. Fifty-four people died.

"Raw sewage got sucked back into the clean water supplies," said Paul
Epstein, associate director of the Center for Health and the Global
Environment at Harvard Medical School. "Cryptosporidium is a parasite
that chlorine doesn't kill, so it escaped water treatment."

On Ohio's South Bass Island in Lake Erie in the summer of 2004, at
least 1,450 residents and tourists suffered gastrointestinal illnesses
linked to several months of above-average rains that contaminated the
town's drinking water.

More than 100 pathogens can cause illness if you drink or swim in
water contaminated by sewage, including norovirus Norwalk and
hepatitis A viruses and bacteria such as E. coli and campylobacter.

"If someone gets something swimming, they could bring it into work or
day care. This is what's happened with cryptosporidium before," said
Joan Rose, a Michigan State University professor and water researcher.
"So we have all these rippling effects that occur in our community."

Combined sewer overflows can be eliminated by upgrading sewerage
systems, but it is an expensive process.

"Here we are in a wealthy country with a very strong public health
infrastructure," said Jonathan Patz, a professor of environmental
studies and population health sciences at the University of Wisconsin
at Madison. "But we need to realize it's not as strong as we thought
it was, and water systems really need tremendous resources for upkeep
in the face of climate change."

A report last week by the National Research Council concluded that the
EPA's storm-water program needs major overhauls to deal with
increasing runoff, including a more integrated permitting system based
on watersheds and a focus on land use by growing municipalities.
Benjamin H. Grumbles, EPA assistant administrator for water, said
Friday that upgrading combined sewer systems is among the agency's top
priorities.

Runoff from agricultural land can also spread waterborne diseases, and
rising water temperatures are conducive to the growth of pathogens
such as naegleria, an amoeba that enters the nasal passages and leads
to often-fatal meningoencephalitis. Warmer waters also trigger blooms
of algae and plankton, which themselves can be toxic or can harbor
pathogens such as the bacteria that cause cholera, as has happened in
Peru and the Bay of Bengal.

Algae blooms are also fostered by nitrogen and phosphorus that are
washed into rivers, lakes and the ocean by heavier rainfalls.

Downpours are likely to lead to more seafood contamination as human
waste, animal manure, nitrogen and phosphorus make their way to
coastal areas.

Epstein said the recent flooding in Texas from Hurricane Ike and the
mosquito infestation that followed are one example of climatic
conditions that are likely to foster more waterborne disease in coming
years, despite efforts by the EPA and the Centers for Disease Control
and Prevention.

"It will be the next few years. This is not 20 years away," Epstein
said. "It's already occurring. The CDC is gearing up to deal with
[it], but at the same time, we need to be focused on the primary
driver, which is our unstable climate. We need to do all of the above
-- protect, prepare and prevent."