The Magazine of the Pan American Health Organization: Volume 6 No. 2 - 2002Each fall, Ms. Josephine Colón, a Head Start teacher in Barceloneta, Puerto Rico, gathers her class for a parade. Masquerading as nurses, doctors, patients, fumigators-even mosquitoes and insecticide cans-the pupils join 400 other three- and four-year-old Head Start students near the center of town.
Accompanied by teachers, fire fighters, and police, they march with sirens blaring a quarter mile up Calle Georgetti, singing songs about dengue fever and handing out fliers to the cheering crowds that flank their route.
In a scene repeated throughout much of Puerto Rico each year, the children bring traffic and commerce to a halt. They parade past schools, pharmacies, supermarkets, restaurants, offices, and banks to an open-air stage in the heart of Barceloneta's central plaza. There, joined by local officials, they read poems and messages about dengue and perform what amounts to a public health morality play.
"Everyone stops to listen to the message of how we can eliminate mosquitoes," says Ms. Colón. And with them, dengue fever.
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 epi-demic 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.
Why has dengue reappeared with such a vengeance? A prime factor is rapid, unorganized urbanization and the proliferation of slums throughout many Latin American cities, which has made it difficult for governments to provide adequate water and sanitation services. Stored water and discarded containers are ideal breeding grounds for Aedes aegypti.
Urbanization has also compounded the costs of traditional surveillance and vector control programs, which have been labor-intensive and heavily reliant on the application of chemicals.
"In the past, programs focused largely on the use of insecticides, and the government did just about everything," says Dr. Gary Clark, chief of the U.S. Centers for Disease Control and Prevention (CDC) Dengue Branch. Spearheaded by PAHO, those programs were so successful that more than 20 countries were certified free of Aedes aegypti.
But that success eventually proved to be an Achilles' heel. In the absence of any immediate threat of dengue, financially strapped Latin American states diverted funds from monitoring and eradication programs to other uses. "Out of sight, out of mind," observes Dr. Arias.
The resulting mosquito reinfestation has become so widespread, according to Dr. Clark, that it is now greater than it was in the 1930s. In response, during 1996 and 1997 combined, 25 countries with endemic dengue spent just over $1 billion total on Aedes aegypti programs. Yet in a study two years ago, PAHO estimated that to extend their programs to all affected areas, these countries would have to spend US$1.3 billion every year.
The nature of dengue, with its cyclical outbreaks every three to five years, leads government health officials faced with competing health and political demands to react with a crisis mentality to emergency epidemics, while in the long term carrying out sporadic, and generally ineffective, responses in non-outbreak years, sometimes even during non-dengue seasons.
"Interventions to control dengue with vertical [government-led] programs have failed," concludes Dr. Guillermo Gonzalvez, national director of the Dominican Republic's National Center for the Control of Tropical Diseases. Echoing the CDC, PAHO, and other dengue experts, Dr. Gonzalvez contends: "We have to rethink a strategy that hasn't worked. We need more cost-effective interventions that produce less harm to the environment and that can be sustainable by the people."
Dr. Arias agrees. "PAHO advocates social communication with community participation and behavioral changes," he says. "Not just with dengue, but also with tobacco and sexually transmitted diseases such as HIV/AIDS, man's behavior is conducive to the disease. The best way to avoid the disease is to change behavior."
Since mosquitoes breed near houses, says Dr. Arias, any intervention must begin at the household level, to eliminate larvae and eggs so they won't produce adults that can transmit the disease.
Yet shifting "ownership" of dengue control from governments to the people presents a serious challenge. "People still think vector control is the government's business," notes Dr. Gonzalvez.
Another challenge is popular misconceptions about dengue itself. For example, a majority of 600 women interviewed in the Mexican Yucatán a dozen years ago believed that dengue-whose symptoms mimic common influenza-was spread by person-to-person contact.
"If you think you get it from other people, you don't care about the 55-gallon water drum in your backyard," says Dr. Linda Lloyd, a public health consultant who developed a pilot intervention project in Mérida in the mid-1990s with support from the Rockefeller Foundation. "They also didn't understand that the larvae in their water containers became adult mosquitoes, so they did nothing about them."
Dr. Lloyd and others say such experience indicates that the one-size-fits-all, top-down approach of governments must be replaced by lo-cally controlled programs that use knowledge of domestic arrangements for water and waste management to involve individuals, families, and communities in dengue control.
In the Dominican Republic, the challenge was how to make the ubiquitous 55-gallon drums used for water storage less hospitable breeding sites for mosquitoes. Dominican families typically have from three to 11 such drums on their property, and 45 percent of Dominican homes produce Aedes aegypti, primarily in the drums, according to Dr. Gonzalvez.
Following Hurricane Georges in 1998, Dr. Elli Leontsini of the Department of International Health at the Johns Hopkins School of Public Health, and Dr. Julia Rosenbaum, a medical anthropologist with the CHANGE project at the Academy for Educational Development, helped Dominican officials launch a dengue research and intervention program sponsored by the U.S. Agency for International Development, the CDC, and PAHO. Eliminating the drums, or hermetically sealing them, wasn't feasible because residents use water from them so frequently throughout the day: for cooking, washing, showers, and laundry.
Following extensive one-on-one interviewing of residents, "our recommendation ultimately was to improve the cleaning procedure that people were already following, because they are concerned about cleanliness in general, if not about mosquitoes," says Dr. Leontsini.
Because Dominicans were already using chlorine bleach to purify water stored in the drums, Dr. Leontsini and Dr. Rosenbaum recommended they use a sponge to dab the bleach-which kills mosquito eggs-on the walls of empty drums. They were then told to toss more chlorine in the bottom of the drums. If folks didn't feel like emptying each drum at least weekly, they could dab bleach on the walls of the drum just above the water line. "If they do that once a week, eventually all the eggs, new and old, will be killed before they have a chance to hatch," says Dr. Leontsini.
Dr. Lloyd, who has conducted and reviewed related research in Honduras and Mexico, says the evidence is clear that "a dengue program absolutely will not be successful unless you understand how the community views not just dengue, but its environment. It's really an environmental issue. Humans create the breeding sites, and the philosophy of behavioralists is that if we create them, we can control them."
The key is to develop locally appropriate solutions that are readily available and that people will embrace. In Honduras, a technique using a paste made of bleach and detergent was dubbed la untadita (the little dab), says Dr. Leontsini. In the limestone-rich Yucatán, notes Dr. Lloyd, two fistfuls of lime per month are now recommended to treat used tires, another potential breeding ground.
To avoid the old top-down syndrome, dengue programs in the Dominican Republic have tapped neighborhood associations such as sports clubs, religious organizations and housewives' groups to spread their message. Although these groups' primary objectives are not health related, they can still be effective, says Ms. Cheila Valera, a government social worker. "The families and women they visit have shown a lot of enthusiasm because they feel that somebody's truly interested in them and their families' health," says Ms. Valera. "The fact that they are visited by a community member, not someone from outside, has special positive significance for these families."
How volunteers present the message is also critical. Using a social communication strategy called Negotiation of Improved Practices, community volunteers begin each home visit by simply asking how the family takes care of its water drums. "There's no mention of dengue or the threat of disease," says Dr. Leontsini. "They talk about cleanliness in general and improvement of health by better cleaning of the most important resource, water."
Near the end of the visit, the volunteer suggests dabbing bleach as an additional practice. "Can you try complete dabbing? Can you try partial? Can you do it once a week?" the volunteer might ask. A week later, the volunteer makes a return visit to reinforce the behavior. "They give the family a chance to try this new behavior," says Dr. Gonzalvez, "and if they like it, if they think it's good, they'll do it."
In the few Santo Domingo neighborhoods where the program was launched last year, preliminary surveys indicate that the number of infested drums may have declined by 30 percent. As a result, the Dominican Republic intends to evaluate the community intervention program more formally and consider implementing it throughout the island nation.
Meanwhile, in Puerto Rico, schoolchildren are being tapped as key agents of behavioral modification in the fight against dengue. The CDC's Dengue Branch, headquartered in San Juan, developed the Head Start dengue program and supports it in conjunction with commonwealth and regional environmental health agencies and local governments. Initiated 15 years ago with support from the San Juan Rotary Club, the program has also re-cruited the Boy Scouts and the Children's Museum of San Juan.
As part of the initiative, every Puerto Rican fourth grader gets instruction in dengue prevention, supported by a teacher's guide that lists about 25 activities to drive home the message.
Besides holding annual dengue fever parades, the Head Start program also organizes public health fairs and a variety of classroom activities from August through February, the peak dengue season on the island. Teachers make mosquito puppets. Children sing songs, do workbooks, and take written materials home to their parents. In some towns, Head Start parents are also being trained to become anti-dengue community leaders.
Although few three- or four-year-olds outside Puerto Rico know the scientific name for any mosquito species, Ms. Josephine Colón's students can not only recite Aedes aegypti's name, but can recognize all its stages (larva, pupa, and adult), thanks to bottled samples provided by the CDC. Some Head Start classes in Puerto Rico even grow their own Aedes aegypti mosquitoes to better understand how the insects grow and reproduce.
Armed with this knowledge, children then carry the word not just to their own homes, but throughout their neighborhoods. Doubling as investigators and evangelists, they roam their communities in search of potential breeding sites: old tires, empty bottles and cans, even pet drinking bowls, if they aren't emptied at least daily.
"With these preventive activities, we're trying to create as much awareness as possible among the children, their families and the community," says Ms. Carmen López, health and early education development manager of Head Start in Barceloneta. "The message is that it's not the federal or local agencies' responsibility; we all have to pitch in because, in the long run, it's our own health we're promoting."
Ms. López describes the program so far as "very effective," noting that between July 2000 and July 2001 in Barceloneta, 44 cases of suspected dengue were referred for further analysis, but all proved negative.
Based on these pilot programs, and given the fact that a vaccine is apparently years away, community interventions that use children and local volunteers might hold the best long-term hope for controlling dengue fever. But this will take time-and a paradigm shift in the mindset of all concerned.
"We have to change behavior," says Dr. Gonzalvez, "not only at the family level, but also at the institutional level. . . from senior officials who still believe in the traditional method of hiring mass media to spread the word, to the middle management of ministries of health who only believe in applying insecticides, even though that method has failed."
In September 2001, all the countries of the Americas approved a resolution strongly supporting integrated action for dengue control at all levels, "recognizing the trend of increasing numbers of cases of dengue and dengue hemorrhagic fever in the Americas." They urged the incorporation of social communication and community participation measures "that encourage positive behavioral changes" into dengue prevention and control programs.
Dr. Arias of PAHO applauds the region's ministers of health for laying out so clearly what their countries must do: promote coordination, stimulate environmental actions, change behavior, provide quality care for dengue patients, standardize reporting, and prepare for outbreaks. "Dengue is a real problem," says Dr. Arias, "and we could have a long uphill battle in the Americas unless we fully implement this plan."
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