While Zaire’s deadly Ebola virus was flaring up briefly, a far more widespread viral scourge was threatening the Americas. In 1995 dengue fever, nicknamed breakbone fever for the terrible joint pain it causes, reached epidemic proportions in Latin America and Caribbean countries, sickening more than 140,000 and killing 38. According to the Centers for Disease Control, dengue has been spiraling out of control for years-- largely because of a 25-year lapse in eradication programs against the mosquitoes that carry the virus. And Latin America, with its explosively growing population and often poor water supply and sanitation, is an excellent breeding ground for those mosquitoes.
Once the virus sneaks into the human bloodstream, it begins to replicate in, and kill, white blood cells. The body’s response is vomiting, fever, and horrific pain. In most cases, however, this acute condition subsides within a week. The real danger comes later.
There are several types of dengue virus, and exposure to one does not provide immunity to the others. In fact, the immune system actually helps a second infection take hold. When the body is first attacked by the virus, it produces antibodies to it. When it is subsequently attacked by a different type of the virus, these antibodies, though unable to kill the virus, still attach to it. At the same time, they also attach to white blood cells and so ease the virus’s entry into those cells, where it plays havoc with the normal immune response. As the infected cells break down, they release a molecule that signals blood vessels to become leaky. Eventually, as more and more white cells die, the vessels leak so much fluid that blood pressure crashes. If the condition is left untreated, the result is deadly shock.
Making the year’s news worse was a report that a new strain of dengue from Southeast Asia had slipped into Latin America. This new strain is being introduced in areas where there are large populations of people who have never been exposed to it, explains José Rigau of the CDC. And of these susceptible people, a large proportion will have had previous dengue infections. This is not just falling on good earth, it is falling on earth that has already been fertilized.