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For much of the last half-century, the only reason to hold a dengue fever parade in the Americas would have been to celebrate its demise. Although sporadic outbreaks occurred around the Caribbean and in Venezuela in the 1960s and 1970s, intensive efforts to control Aedes aegypti-the daytime-biting mosquito that is the vector for dengue fever-rendered most of North, Central, and South America free of major outbreaks of epidemic dengue fever for many years.
 In 1981, however, the spell was broken when Cuba was struck by an epidemic of classic dengue and dengue hemorrhagic fever (DHF). Hundreds of thousands of people came down with classic dengue symptoms: fever; weakness; severe head, back, and muscle pain; and a bright red rash. Of the 10,312 cases of DHF, 159 deaths were reported.
Today, about two-fifths of the world's population is at risk for dengue, and more than 100 countries have experienced dengue or DHF outbreaks. The annual incidence of the disease is up to 50 million cases per year worldwide, of which 500,000 are hospitalized and 20,000 die. Ninety-five percent of all DHF cases are children under 15 years of age.
In the Americas, the situation has become progressively more alarming, with an increase in both dengue and DHF, with its much higher fatality rate.
As Dr. Jorge Arias, regional adviser on communicable diseases for the Pan American Health Organization (PAHO), explains, dengue has four distinct but closely related viral serotypes. "The first time a person becomes infected with one of these, usually only dengue fever results," says Dr. Arias, "and patients then become immune to that serotype." But a subsequent infection with any of the other three serotypes can result in DHF, whose symptoms include hemorrhages from the nose and mouth, bleeding under the skin, and in some cases, shock and death.
 After the 1981 epidemic in Cuba, the number of dengue cases reported in the region remained under 200,000 per year until the mid-1990s, then rose steadily to more than 700,000 in 1998. The numbers have declined during the last two years, although PAHO officials believe that the true picture may be distorted by underreporting and some countries' practice of reporting only lab-confirmed cases.
In fact, during 2000 there were dengue epidemics in Costa Rica, Cuba, Ecuador, El Salvador, Guatemala, Honduras, Nicaragua, Paraguay, and Suri-name. In 2001, epidemics were reported in Brazil, Ecuador, Peru, and Venezuela.
Last October, Hawaii State Health Director Bruce Anderson said that dengue fever was now established on the island of Oahu. He warned that the disease could potentially infect everyone in Hawaii, causing serious illness in 200,000 people, unless mosquitoes are controlled.
Hawaii "will throw everything we have at it," Mr. Anderson told the Honolulu Advertiser, calling on every citizen of the state to help.
But as Mr. Anderson himself admits, few communities-let alone entire countries-have been able to stop dengue fever from running its course. Without DDT and the other powerful, toxic pesticides of the past, dengue fever usually stops only when the virus has been transmitted to most of the population, causing serious illness in about 20 percent but conferring immunity to that strain of dengue for the future.
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