<http://www.latimes.com/news/science/la-sci-disease25feb25,0,7795423.story?coll=la-home-headlines>http://www.latimes.com/news/science/la-sci-disease25feb25,0,7795423.story?coll=la-home-headlines
Global warming: enough to make you sick
Rising temperatures are redistributing bacteria,
insects and plants, exposing people to diseases
they'd never encountered before.
By Jia-Rui Chong
Times Staff Writer
February 25, 2007
CORDOVA, ALASKA Oysterman Jim Aguiar had never
had to deal with the bacterium Vibrio
parahaemolyticus in his 25 years working the
frigid waters of Prince William Sound.
The dangerous microbe infected seafood in warmer
waters, like the Gulf of Mexico. Alaska was way too cold.
But the sound was gradually warming. By summer
2004, the temperature had risen just enough to
poke above the crucial 59-degree mark. Cruise
ship passengers who had eaten local oysters were
soon coming down with diarrhea, cramping and
vomiting the first cases of Vibrio food
poisoning in Alaska that anyone could remember.
"We were slapped from left field," said Aguiar,
who shut down his oyster farm that year along with a few others.
As scientists later determined, the culprit was
not just the bacterium, but the warming that allowed it to proliferate.
"This was probably the best example to date of
how global climate change is changing the
importation of infectious diseases," said Dr. Joe
McLaughlin, acting chief of epidemiology at the
Alaska Division of Public Health, who published a study on the outbreak.
The spread of human disease has become one of the
most worrisome subplots in the story of global
warming. Incremental temperature changes have
begun to redraw the distribution of bacteria,
insects and plants, exposing new populations to
diseases that they have never seen before.
A report from the World Health Organization
estimated that in 2000 about 154,000 deaths
around the world could be attributed to disease
outbreaks and other conditions sparked by climate change.
The temperature change has been small, about 1.4
degrees Fahrenheit over the last 150 years, but
it has been enough to alter disease patterns across the globe.
In Sweden, fewer winter days below 10 degrees and
more summer days above 50 degrees have encouraged
the northward movement of ticks, which has
coincided with an increase in cases of tick-borne encephalitis since the 1980s.
Researchers have found that poison ivy has grown
more potent and lush because of increased carbon dioxide in the atmosphere.
In Africa, mosquitoes have been slowly inching up
the slopes around Mt. Kenya, bringing malaria to
high villages that had never been exposed before.
"It's going to get very warm," said Andrew
Githeko, a vector biologist who heads the Climate
and Human Health Research Unit at the Kenya
Medical Research Institute in Kisumu. "That's
going to mean a huge difference to malaria."
Githeko, 49, grew up in the central highlands in
a tiny village near the town of Karatina, about 5,700 feet above sea level.
His home was different from most of Africa. The
air was damp and chilly. On clear days, he could
see the glaciers on Mt. Kenya, the second-highest
peak in Africa at 17,058 feet.
When he was a child, lowland diseases like
malaria were unknown in Karatina. But perhaps 10
years ago, a smattering of cases began to appear.
He had long ago left his home to study the great
plagues of Africa Rift Valley fever, malaria,
cholera and others. The appearance of malaria in
the highlands, however, was a mystery worth returning home for.
Githeko dispatched a colleague to collect
mosquito larvae in puddles and streams around Mt.
Kenya, some as high as 6,300 feet. Tests later
identified some of the mosquitoes as Anopheles
arabiensis, one of the species that carry malaria.
Githeko's findings, published in 2006, marked the
highest A. arabiensis breeding site ever recorded
in Kenya and was the first published report of
malaria infections in the central highlands, he said.
He knew by watching Mt. Kenya's gradually
disappearing glaciers that his world was warming,
and that lowland diseases would eventually work
their way higher. "But we did not expect this to happen so soon," he said.
Githeko's work has been echoed in a small number of studies around the world.
In 1996, health authorities reported a human case
of tick-borne encephalitis in the Czech village
of Borova Lada, elevation 3,000 feet. Until then,
the Ixodes rinicus tick, which carries the
disease, had never been seen above 2,600 feet.
The case caught the attention of Milan Daniel, a
parasitologist the Institute for Postgraduate
Medical Education in Prague who has been studying
the movement of ticks in the Czech Republic for half a century.
He scoured the Sumava and Krkonose mountains and
found that the ticks had migrated as high as
4,100 feet largely because of milder autumns over
the last two decades, according to a series of
studies published over the last four years.
From 1961 to 2005, the mean temperature in the
Krkonose Mountains had increased about 2 1/2 degrees.
"This shift of the ticks," Daniel said, "is
clearly connected with climate changes."
According to a landmark United Nations report
released this month, global warming has reached a
point where even if greenhouse gas emissions
could be held stable, the trend would continue for centuries.
The report painted a grim picture of the future
rising sea levels, more intense storms, widespread drought.
Predicting the future of disease, however, has
proven difficult because of myriad factors many
of which have little to do with global warming.
Diseases move with people, they follow trade
routes, they thrive in places with poor
sanitation, they develop resistance to medicines,
they can blossom during war or economic breakdowns.
"No one's saying global warming is the whole
picture here," said Dr. Paul R. Epstein,
associate director of the Center for Health and
the Global Environment at Harvard University.
"But it is playing a role. As climate changes,
it's projected to play an even greater role."
In a Beltsville, Md., laboratory filled with
bathroom-sized aluminum chambers, U.S. Department
of Agriculture weed physiologist Lewis Ziska is
peering into the future of one of the key
components of global warming rising carbon dioxide levels.
CO2 levels have been on the rise since the dawn
of the Industrial Revolution more than 200 years
ago. Today, they are at their highest point in more than 650,000 years.
In the tightly sealed chambers, Ziska re-created
pre-industrial conditions by turning down the
concentration of carbon dioxide to 280 parts per
million. In another box, he simulated the present
with 370 parts per million. In a third box, he
pumped up the carbon dioxide to 600 parts per million, the estimate for 2050.
Much of Ziska's work has centered on ragweed, a
noxious plant that sets off allergy sufferers,
such as Ziska himself. The weeds inside the tanks
suck up carbon dioxide. "It's like feeding a hungry teenager," he said.
Collecting yellow pollen in plastic bags fitted
around the plants, Ziska found that current
conditions produced 131% more pollen than
pre-industrial conditions. Future conditions produced 320% more.
"For us weed biologists, this is the worst of
times and the best of times," he said.
The impact of global warming has not been all
bad. Researchers recently found that rising
temperatures have helped reduce some diseases
related to cold weather. One British study found
that the number of children infected with a
cold-like virus known as respiratory syncytial
virus has been declining with warming temperatures.
Combining meteorological data and emergency room
admission rates from 1981 to 2004, physiologist
Gavin Donaldson at University College London
found each increase of 1.8 degrees clipped three
weeks off the end the virus' winter season.
"A small amount of warming can go a long way, as
far as changing disease transmission dynamics,"
said Dr. Jonathan Patz, director of Global
Environmental Health at the University of Wisconsin in Madison.
Given the gradual pace of warming, there are also some chances to adapt.
After Prince William Sound's Vibrio outbreak in
2004, the state required more oyster testing in
some areas. In the last two years, there have
been only four cases of Vibrio food poisoning.
Life in Aguiar's remote inlet has largely
returned to the way it was before. This winter
has been cold. Aguiar, a bear of a man with a
riotous beard, huddled inside the houseboat for
warmth recently as the temperature outside
hovered around 20 degrees. The pale Northern
Lights pulsed over the snow-laced Chugach
Mountains, and skins of ice grew on the still water.
Come summer, Aguiar will start sending oyster
samples to the state. When the temperature hits
about 55 degrees, he'll drop his oyster baskets
60 or 100 feet in the water for about 10 days to clear out the bacteria.
It's a solution he can live with in a warming world.
"It's not all evil," he said. "I just don't like to see rapid change."
