Asia shows way to fight dengue
Due to international travel and climate change, the Aedes aegypti
mosquito’s habitat is spreading.
Clarissa Poon was one of an estimated 50 million people who
contracted mosquito-borne dengue fever last year. She spent an agonising
week on a drip in a Bangkok hospital as she battled the potentially
deadly disease.
“There was not a single moment when I wasn’t aching everywhere, dizzy
and nauseous. I was so weak I couldn’t even stand,” said Poon, who
caught the illness during a family holiday at a beach resort in
Thailand.
“My
kids were very worried because the mother of one of their friends died,”
she added.
From Africa to Asia to Latin America, around 2.5 billion people live
in areas that are at risk of dengue fever, a viral disease spread by the
Aedes aegypti mosquito.
There is no vaccine or drugs to treat the illness which killed an
estimated 22,000 people last year, most of them children.
Due to international travel and climate change, the Aedes aegypti
mosquito’s habitat is spreading.
In January, health officials warned that the disease was poised to
move across the United States. It has been spreading aggressively in
Latin America and the Caribbean, reaching epidemic levels last year.
Dengue is endemic in Southeast Asia where a tropical climate and monsoon
rains provide ideal conditions.
Strategies developed in places such as Singapore might provide vital
information for other countries seeking to combat the virus and the
mosquitoes that spread it.
Family doctors in Singapore look out for patients with suspicious
symptoms. When cases are confirmed, researchers try to nail down the
specific dengue virus subtype, of which there are four, and the location
of the outbreak.
“You need to monitor what (subtype) is going around ... You want to
limit the damage, the fatalities,” the World Health Organisation’s
advisor in Asia, John Ehrenberg, told Reuters.
While dengue and malaria share geographical patterns, dengue is more
dangerous because its mosquito carriers thrive indoors. Mosquitoes that
carry malaria are rarely found in urban areas.
Dengue fever is endemic in more than 100 countries in Africa, the
Americas, eastern Mediterranean, Southeast Asia and western Pacific.
Of the 50 million people who contract the disease every year, about
one percent get potentially deadly severe dengue haemorrhagic fever (DHF),
which requires hospitalisation.
There is no cure or vaccination for dengue fever. Sufferers such as
Poon, face an increased likelihood of developing DHF if they contract
the disease again, which is not uncommon for those living in the tropics
where the mosquito carriers flourish.
No stopping it?
International travel has made the spread of dengue inevitable,
experts say.
“There is always a risk for the borders ... In central America, you
have a lot of people moving up north,” Ehrenberg said. “There is a risk
of people moving in with dengue.”
Ehrenberg says there is little to stop dengue from spreading. He
compares it to West Nile virus which appeared in New York in 1999 and
then spread across the United States, Canada and Mexico. West Nile
killed 98 people in the United States last year.
“As you can see with West Nile virus, there is hardly anything you
can do to control its spread in the U.S. It’s all over the place now.
There’s always the risk of introducing, when the climatic conditions are
right,” Ehrenberg said.
Both dengue and West Nile are spread by mosquitoes.
“It’s a neglected disease because no one pays attention in between
outbreaks, except in places like Singapore, where there is very good
surveillance,” Ehrenberg said.
In Singapore, health workers aggressively control breeding sites by
regularly spraying pesticides in parks and gardens. Government
inspectors fine people for allowing water to build up in flower pots
which is a favourite breeding site.
Singapore reported 14,000 dengue cases in 2005, but that fell to
3,597 cases in the first half of 2007, according to the WHO.
With 42,456 cases in 2006 and 45,893 in 2005, Thailand figures near
the top of the dengue list. Fanned out across the country are 500,000
volunteers who educate villagers on mosquito control, chiefly by
removing stagnant pools of water.
Kitti Pramathphol, head of Thailand’s dengue control, said more
inspections would be made to remove potential breeding sites before the
rainy season in June and July, when the disease peaks. |