Health: INFECTIOUS DISEASES: 'BREAK BONE FEVER'
Dengue fever: spreading and often undiagnosed
Travellers are sometimes unaware they have contracted the illness, leaving them vulnerable to more dangerous subsequent infections
The Canadian Press
July 1, 2008
It goes by the nickname "break bone fever." And after his brush with dengue fever, Phil Day knows why.
Mr. Day, an expatriate Canadian living in Singapore, contracted the mosquito-borne viral disease in 2007 after years of working in cities across Asia. He and his wife, Karen, were both afflicted, struggling through an illness that left them exhausted and in pain.
While they were sick, they needed to be monitored for signs they were developing the severest form of the disease, a life-threatening hemorrhagic fever (neither did). That monitoring required them to go to hospital for daily blood tests. On one of those trips, Mr. Day saw a sight that embodied how he was feeling.
"We were waiting at a traffic light and this old guy, probably 90 years old or so, crossed the street with a cane. He was moving very slowly and every step looked painful," he recounts via e-mail.
"And I turned to my wife and said: 'That's it. That's exactly how I feel.' "
Dengue fever is a disease of warm climes; Canada's cold winters deter the virus from setting up shop here.
But the thousands of Canadians who travel to the wide swaths of the world where the virus does spread are at some risk of becoming infected with a virus that can trigger symptoms ranging from flu-like fatigue and aching joints to a hemorrhagic fever that can kill.
A newly published study looking at trends in dengue infections in travellers notes that the past 20 years have seen a marked expansion of the virus's turf, from Southeast Asia to the islands of the South Pacific, the Caribbean and the Americas. There have even been domestically acquired infections in the United States.
Dengue fever has become a more common diagnosis than malaria for ill travellers returning from tropical regions other than Africa, notes the study, published in the July issue of Emerging Infectious Diseases.
An analysis of cases reported to the GeoSentinel Surveillance Network, an international collaboration of specialized travel and tropical medicine clinics, shows that from October, 1997, through February, 2006, 522 of nearly 25,000 ill travellers seen at network clinics were diagnosed with dengue or dengue hemorrhagic fever.
While that is only 2.1 per cent, it is also only a fraction of the cases that would have occurred during that period, says one of the study's authors, Kevin Kain. Not everyone who falls sick after a trip will end up at a travel clinic.
"Many people will have ... feverish illnesses that don't progress and they just stay at home," says Dr. Kain, director of the travel and tropical medicine clinic at Toronto's University Health Network.
"Or they present to their GP and no one ever does a confirmation test - no one ever does [blood testing]. So this is the tip of the iceberg, the cases we're seeing."
Anyone who has had dengue fever once faces a much higher risk of developing dengue hemorrhagic fever if they contract the disease again. Nine out of 10 cases of dengue hemorrhagic fever occur in people who have previously had dengue fever, Dr. Kain says.
"The first time you get it you feel like you're going to die, but you survive. But it's the subsequent infections [that are dangerous]. So people want to know if they've actually had dengue, because then they're a little more apprehensive about subsequent exposures."
Every year, an estimated 50 million to 100 million people worldwide contract dengue fever, according to the U.S. Centers for Disease Control. And several hundred thousand people come down with dengue hemorrhagic fever.
In Canada, 40 to 50 laboratory-confirmed cases of dengue fever are reported every year, in travellers who have visited parts of the world where the type of mosquito that spreads the virus are found.
Protecting against infection poses real challenges for travellers in these areas. There is no vaccine and, unlike for malaria, no pills that block infection. So it comes down to DEET-based insect repellents and luck.
The disease cannot spread from person to person directly, though mosquitoes become infected by drawing blood from an infected person and then pass the virus along.
The disease typically manifests itself with a high fever, severe headache, backache, joint pains, nausea and vomiting, eye pain and rash. Younger children usually suffer milder disease than older children and adults.
In a portion of cases, though, the hemorrhagic syndrome develops. Blood begins to pool under the skin and there can be bleeding from the nose and gums and even internal bleeding. Blood vessels become leaky, which can lead to blood loss, circulatory system failure, shock and death.
There are no drugs to combat the virus. But with good care - which largely involves replacing fluids - most people will survive. The earlier treatment starts, however, the better.
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