Here in the Philippines, when the monsoon hits, we start with cases of Dengue fever. It is spread by mosquitoes, and since in the rainy season puddles and open ditches are full of mosquito larvae, it is a problem. Since mosquitoes tend to love me, it means that I avoid going outside in the late afternoon and evening, and wear long pants and sleeves.

Of course, cities do spray the ditches and encourage people to eliminate mosquito breeding areas such as puddles, tires, and old basins. Here the TV reminds you to check your house for standing water, such as pans or tires. It’s called the four o’clock habit, to distinguish it from the Three o’clock habit, which is a Jesus devotion called the divine Mercy, where you pray at three o’clock for the sins of the world. Probably both habits are just as widespread, and probably just as effective at cleaning up the country. The mosquito that carries Dengue A Aegyptae, is a common one, and carries several other diseases such as yellow fever. It is not the same mosquito that carries Malaria, but the control methods are the same: Drain breeding grounds, spray insecticide, use screens and mosquito netting, and use insect repellents.
Dengue has another name: Breakbone fever, since generalized pain is one of the main symptoms, along with fever. In mild cases, people just sit home, but in bad cases, it is a “hemorrhagic” fever, meaning it can cause generalized bleeding, rash, liver enlargement and kidney shut down. Most of the deaths are in children, which makes it especially tragic, and there are no antibiotics to stop the infection, although “supportive care” keeps down the death rate.

Dengue has probably been around for years, but may not have been recognized in lands where fevers of various sorts were common. Historically, today’s epidemic started after World War II and spread throughout South East Asia and South and Central America. However, the presence of outbreaks in dozens of widely separated areas including the Americas suggest the infection probably had been present but quiescent. The historical trend was epidemics every 10 to 40 years suggesting that most people got the disease, and probably most cases were mild. Then since the population had post infection resistance, the epidemics cleared until another generation of people grew up to get the disease. Or maybe it is just that new strains of the virus appear, since other articles state that if you get Dengue a second time it’s more severe.

Control methods probably contributed to the decrease in the disease after World War II, but it has had a resurgence since the 1980’s.

There are a lot of theories on why this has happened.

Is this epidemic due to Global warming, as the IHT (NYTime European paper) claims? If so, then why did one fifth of the population of Philadelphia die of Yellow fever, a disease that is carried by the same mosquito as Dengue, back in 1790’s?
Or is it merely the latest upsurge of an epidemic cycle that is now more easily diagnosed in the increasingly urban third world? Or is another epidemic that can be laid at the feet of Rachel Carson’s crusade to save birds from DDT?
I don’t know. None of these articles discuss the possibiity that the increase of Dengue, like the increase of Malaria, is due to the pull back of using DDT to control the vectors.

The NEJM article touts the importance of habitat control, which is after all the way Yellow fever was largely eliminated, and mentions that DDT was also used to control the moquitoes. Here is the entire paragraph, and note that it is only one of several things needed to eliminate the problem.

Perhaps the best-known example of a successful vector-reduction strategy is the U.S. campaign to eradicate yellow fever and malaria during the construction of the Panama Canal. In that case, a comprehensive plan that included drainage of standing pools of water, cutting of grass and brush, oiling of ponds and swamps to kill larvae, and capture of indoor mosquitoes resulted in the eradication of yellow fever and a substantial reduction in cases of malaria. In the 1930s and 1940s, similar efforts toward mosquito control in the southeastern United States, as part of a program of the Tennessee Valley Authority, led to the near-eradication of endemic malaria in the United States. Insecticidal spraying with dichlorodiphenyltrichloroethane (DDT) was begun in this country in the late 1940s as part of the National Malaria Eradication Program and helped to eliminate the few remaining cases of malaria in the United States. However, although initially hailed as a panacea, spraying with DDT has not been effective at eradicating malaria worldwide. Well-publicized problems with environmental toxicity, the possibility of human carcinogenesis, and the development of resistance among insects have led to the withdrawal of DDT from widespread use.

So all the DDT in the world won’t work if the infrastructure isn’t controlled. But I suspect much of today’s epidemic is more due to environmentalism’s ban of DDT than the global warming.
Or maybe history is right: it’s a normal cycle of the disease.

Whatever is the truth, the dirty little secret is that Dengue is part of the monsoon cycle, and will probably remain so until vaccines are developed. But in the meanwhile, until people are wealthy enough to afford screens on their houses, it will be up to the local politicians to eliminate breeding areas by drainage, public awareness, and insecticide spraying.

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Nancy Reyes is a retired physician living in the rural Philippines. Her website is Finest Kind Clinic and Fishmarket, and she writes medical essays at Hey Doc Xanga Blog

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