October 5, 2005
Climate change linked to cruise ship illness outbreaks
By Gene Emery
BOSTON (Reuters) - Warming ocean waters may have tainted
Alaskan oysters with a bacteria that triggered four outbreaks
of illness on a cruise ship among people who ate the shellfish
raw, researchers reported on Wednesday.
"The rising temperatures of ocean water seem to have
contributed to one of the largest known outbreaks of Vibrio
parahaemolyticus in the United States," said Joseph McLaughlin
of the Alaska Department of Health and Social Services,
referring to the bacterium responsible for outbreak.
He and his colleagues said 62 people fell ill on four
week-long cruises in July 2004. Vibrio parahaemolyticus is the
most common cause of seafood-related illness in the United
"Alaskan waters were thought to be too cold to support"
bacteria levels known to cause the illness, said the McLaughlin
team. But when they tracked the outbreaks, the source turned
out to be an oyster farm in Prince William Sound, 621 miles
north of any previous source of tainted oysters.
Further tests showed that other oyster facilities in
Alaska's Kachemak Bay and southeast Alaska had also begun to
harbor the bacteria, which is only believed to grow in oysters
where water temperatures are higher than 59 F (15 degrees
Temperature records from the area showed that the waters
were more tepid than at any time in recent history. The data
also showed that temperatures at the site have climbed
gradually since 1976.
Based on the study in the New England Journal of Medicine,
"we can't say why ocean temperatures are rising," McLaughlin
But many climate experts have warned that warmer ocean
waters are a likely consequence of carbon dioxide pollution,
which traps heat that would normally radiate back into space.
Scientists predict that warmer temperatures will generate
stronger storms and shift local climate conditions, spreading
various illnesses to new regions.
"This is probably some of the best evidence to date that
rising temperatures in ocean waters might contribute to the
incidence of disease," said McLaughlin, "so we're definitely
The researcher said when water temperatures at oyster farms
exceed 15 degrees Celsius, health officials should test for the
virus, oyster nets should be moved to cooler waters, and the
public should be warned to cook oysters before eating them.
As a result of the findings, nets have been moved to cooler
waters. "That seems to have worked," the researcher said.
Most of the cruise ship travelers who fell sick had eaten
just one raw oyster. The bacteria took 12 to 36 hours to make
Although it is seldom fatal, people with liver disease,
diabetes or immune system problems such as AIDS may die from
the infection, which killed 20 people in 2004, according to the
Center for Science in the Public Interest.