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Dengue Fever: Growing Threat Rivals Malaria, Ebola, Experts Say
Brian Handwerk
for National Geographic News
October 18, 2006
An outbreak of dengue fever in India has infected more than 5,700 people and killed 103 in the past seven weeks.
The deadly outbreak represents only a small fraction of the estimated 100 million infections that now occur every year worldwide.
Formerly under control in some parts of the world, the mosquito-borne disease has made a rapid resurgence in recent decades, leading scientists to put dengue on par with better-known killers like malaria and the Ebola virus as a global health threat.
"As a public health problem, dengue ranks right up there," said Duane Gubler, director of the Asia-Pacific Institute for Tropical Medicine and Infectious Diseases at the University of Hawaii in Honolulu.
"If you look at vector-borne diseases [those passed by ticks or mosquitoes], it is number two after malaria."
The disease itself is rarely fatal, but a more serious complication, dengue hemorrhagic fever (DHF), is far more dangerous.
DHF can cause liver enlargement and circulatory failure.
Without treatment, DHF can kill 20 percent of its victims. With medical treatment, the fatality rate can drop below one percent.
But as the current crush of patients at hospitals in northern India attests, an outbreak in a region with limited access to health care can take a drastic toll on a community.
"If you just look at the case fatality rate, then it's not so dangerous," Gubler said.
"But if you compare [dengue's overall impact] to [that of] Ebola and Marburg?these highly fatal hemorrhagic fever diseases that get a lot of press?they aren't even in the same league. I consider them relatively unimportant compared to dengue."
Dengue has been known to science for over 200 years and was sometimes called "break-bone" fever because of the muscle and joint pain that characterizes the disease.
In recent decades the four known viruses that cause the disease?for which there are no vaccines as yet?have become more dangerous and widespread.
According to the World Health Organization (WHO), only nine countries had reported DHF epidemics before 1970.
That number has risen more than 400 percent in the past 35 years.
Dengue's growth reflects the ability of diseases to spread in an increasingly globalized world.
The disease's rise also mirrors unprecedented growth in urban and suburban areas, where it is most common.
Human habitat provides ideal breeding grounds for the Aedes aegypti mosquitoes that spread the disease.
Standing water provides attractive breeding locales for the insects. Poor waste disposal makes the problem worse.
"Right now the only way you can control dengue is to control the mosquitoes in urban areas with environmental management," Gubler said.
The disease is less prevalent in affluent countries, even when mosquitoes are present.
Air-conditioned, insect-proof homes reduce the contact that spreads dengue while better health care boosts recovery rates.
But in many growing tropical cities, efforts to prevent the disease's spread are not always successful.
Governments don't have the resources to go door to door, securing homes and eliminating mosquito breeding areas.
"The people have to start doing their own source reduction," said entomologist Jorge Arias of Virginia's Fairfax County Health Department.
Arias formerly ran the dengue program at the United Nations' Pan American Health Organization.
"What's happening now is that government programs cannot handle the problem, and the people are the ones that are [inadvertently] breeding the mosquitoes," he said.
But the disease has been controlled successfully before.
"One of the great successes in the history of tropical disease control is the elimination of mosquito breeding sites from most of the tropical Americas in the 1950s and 1960s. That controlled dengue and also yellow fever," Gubler explained.
Such programs went by the wayside in the 1970s, and now dengue is back with a vengeance.
"It was a classic example of success breeding failure," Gubler said. "Basically the program was so successful that neither of those diseases was a public health problem in the 1970s?and the program was dropped."
Brian Handwerk
for National Geographic News
October 18, 2006
An outbreak of dengue fever in India has infected more than 5,700 people and killed 103 in the past seven weeks.
The deadly outbreak represents only a small fraction of the estimated 100 million infections that now occur every year worldwide.
Formerly under control in some parts of the world, the mosquito-borne disease has made a rapid resurgence in recent decades, leading scientists to put dengue on par with better-known killers like malaria and the Ebola virus as a global health threat.
"As a public health problem, dengue ranks right up there," said Duane Gubler, director of the Asia-Pacific Institute for Tropical Medicine and Infectious Diseases at the University of Hawaii in Honolulu.
"If you look at vector-borne diseases [those passed by ticks or mosquitoes], it is number two after malaria."
The disease itself is rarely fatal, but a more serious complication, dengue hemorrhagic fever (DHF), is far more dangerous.
DHF can cause liver enlargement and circulatory failure.
Without treatment, DHF can kill 20 percent of its victims. With medical treatment, the fatality rate can drop below one percent.
But as the current crush of patients at hospitals in northern India attests, an outbreak in a region with limited access to health care can take a drastic toll on a community.
"If you just look at the case fatality rate, then it's not so dangerous," Gubler said.
"But if you compare [dengue's overall impact] to [that of] Ebola and Marburg?these highly fatal hemorrhagic fever diseases that get a lot of press?they aren't even in the same league. I consider them relatively unimportant compared to dengue."
Dengue has been known to science for over 200 years and was sometimes called "break-bone" fever because of the muscle and joint pain that characterizes the disease.
In recent decades the four known viruses that cause the disease?for which there are no vaccines as yet?have become more dangerous and widespread.
According to the World Health Organization (WHO), only nine countries had reported DHF epidemics before 1970.
That number has risen more than 400 percent in the past 35 years.
Dengue's growth reflects the ability of diseases to spread in an increasingly globalized world.
The disease's rise also mirrors unprecedented growth in urban and suburban areas, where it is most common.
Human habitat provides ideal breeding grounds for the Aedes aegypti mosquitoes that spread the disease.
Standing water provides attractive breeding locales for the insects. Poor waste disposal makes the problem worse.
"Right now the only way you can control dengue is to control the mosquitoes in urban areas with environmental management," Gubler said.
The disease is less prevalent in affluent countries, even when mosquitoes are present.
Air-conditioned, insect-proof homes reduce the contact that spreads dengue while better health care boosts recovery rates.
But in many growing tropical cities, efforts to prevent the disease's spread are not always successful.
Governments don't have the resources to go door to door, securing homes and eliminating mosquito breeding areas.
"The people have to start doing their own source reduction," said entomologist Jorge Arias of Virginia's Fairfax County Health Department.
Arias formerly ran the dengue program at the United Nations' Pan American Health Organization.
"What's happening now is that government programs cannot handle the problem, and the people are the ones that are [inadvertently] breeding the mosquitoes," he said.
But the disease has been controlled successfully before.
"One of the great successes in the history of tropical disease control is the elimination of mosquito breeding sites from most of the tropical Americas in the 1950s and 1960s. That controlled dengue and also yellow fever," Gubler explained.
Such programs went by the wayside in the 1970s, and now dengue is back with a vengeance.
"It was a classic example of success breeding failure," Gubler said. "Basically the program was so successful that neither of those diseases was a public health problem in the 1970s?and the program was dropped."
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