A Tropical Disease Gets Topical

As

a TIME correspondent in Mexico, India, Pakistan and other countries where rogue germs abound, Tim McGirk has had his share of firsthand epidemiological experience. But dengue fever holds a special, painful place in his memory. "There's a reason they call it break-bone fever," says McGirk, who contracted the virus in New Delhi and suffered for three weeks. "You feel like there's this deep, painful itching happening inside your bones. You're on this horrible roller-coaster ride of hot spells and chills, like you're being shaken around. It just racks your body."

Millions of others are being taken on the same ride. According to the World Health Organization (WHO), dengue infects more than 100 million people a year—and the mosquito-borne sickness is on the rise. Once confined to tropical regions like Southeast Asia, 100 countries are now classified as dengue risk areas, up from nine prior to 1970. "Dengue is being seen in places it hasn't been seen before," says Dr. John Simon, a tropical disease specialist in Hong Kong, where a furor over the fever has been roiling local newspapers since the first locally contracted case was reported last month. "Dengue is a huge problem."

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It's big trouble in a tiny package—specifically, the Aedes aegypti mosquito, whose bite is the main way the virus can spread. Aedes aegypti are right at home in tropical cities rife with stagnant water and human targets. "Once a dengue epidemic is under way, it's very difficult to stop it," says Dr. Ray Arthur, a virologist for the who. No vaccine exists.

Fortunately for most, the virus is fatal in less than 1% of cases, although its symptoms—blinding headaches, spiraling fever and extensive body rash—can make death look attractive. Doctors sometimes confuse a dengue case with ordinary flu (the sensitive, pinkish rash is often the best indicator of dengue). But the worst suffering rarely lasts more than a week. Treatment consists of little more than bed rest and nonaspirin painkillers.

A very small percentage of infections can develop into the far more serious dengue hemorrhagic fever (DHF), characterized by bleeding through bodily orifices and even the pores of the skin. In those who have contracted DHF, the body's tiniest blood vessels start leaking like bad plumbing, leading to a catastrophic drop in blood pressure, followed by shock and very often death. Half of those who get DHF will die without top-class medical attention, says Simon. Fluids must be administered intravenously and precisely to keep vascular pressure at a safe level. It can be tough to tell when dengue has developed into DHF, but as microbiologist Dr. Malik Peiris notes, "If you begin to bleed out your orifices, it's pretty obvious you need medical help."

Unlike many viral ailments such as chicken pox, dengue infection fails to ensure immunity from subsequent attacks. Worse, it can actually increase the odds you'll get DHF should you be twice-bitten by dengue-carrying mozzies. The virus comes in four strains, and when antibodies created by one type interact with antibodies created by another type, dengue gets nastier. "This is what is called antibody enhancement phenomenon," says Peiris. It's why a vaccine has so far eluded scientists. "The worry is that if you immunize someone without immunizing them against all four types, it might actually be worse."

With a vaccine not exactly at the front of drug companies' R.-and-D. line, dengue prevention comes down to mosquito prevention. "If you control the mosquito, you control the spread," says Arthur. Unlike the malarial mosquito and vampires, the Aedes aegypti only bites during the day. Keep your home free of potential mosquito-breeding grounds by clearing out any stagnant-water containers such as used tires. Once confined to the tropics, dengue looks to be spreading to new areas in Asia, as the recent Hong Kong outbreak shows. The best we can do is not put out the welcome mat.