By Patricia Grogg
HAVANA, Aug 14 2002 (IPS)

Authorities in Cuba have incorporated environmental controls into their public health efforts aimed at preventing new outbreaks of dengue, since the latest epidemic, which broke out last year.

As part of the new strategy, authorities have begun to identify and eliminate the breeding-grounds of the Aedes aegypti mosquito, which transmits dengue, a viral disease present in tropical and – increasingly – subtropical regions. There is no cure for dengue, which can be fatal in its most deadly forms.

“We have carried out a very serious study since the latest epidemic, and the new focus is on environmental controls, as the best method of prevention,” Guadalupe Guzmán, the director of the virology department at Cuba’s Pedro Kouri Institute of Tropical Medicine, told IPS.

The Institute is working with the Centre of Genetic Engineering and Biotechnology, and the Finlay Institute – also based in Havana – to come up with a vaccine against dengue.

The dengue outbreak in Havana, which began in mid-2001 and did not peter out until March, drew attention to the severe environmental and hygiene problems caused by the accumulation of garbage in people’s backyards and empty lots.

Authorities in Havana, a city of 2.2 million, have now adopted stricter environmental and health measures, stepping up garbage collection, carrying out weekly fumigations of homes, treating water held in storage tanks and other containers, and putting dengue patients in quarantine.

Guzmán said health officials had realized the need to pinpoint the areas where conditions are favourable to the breeding of the Aedes aegypti mosquito.

“The role of the community is very important, because above and beyond government efforts to guarantee water supplies (which are irregular, leading people to collect water in containers) and to pick up garbage in the cities, people must change the way they think and act” in order to effectively combat the disease, she added.

Guzmán pointed out that Cuba and Singapore were among the few countries that had met with success in curbing the spread of dengue, which has caused enormous suffering in Central America, especially El Salvador, this year.

The density of mosquitos is growing as urban poverty expands, because the conditions in overcrowded city slums that lack clean water, sewage systems and garbage collection services create an ideal breeding-ground for mosquitos, which need standing water – which can be found in empty tires, flower pots, or any kind of empty container – in which to lay their eggs.

Slums are growing around large cities in most of the countries of Latin America, which is beginning to face a situation like that of southeast Asia, where dengue epidemics occur every year, said Guzmán.

She added that all four types of dengue can already be found in some parts of Latin America, while several nations have experienced simultaneous outbreaks of two or three serotypes. In addition, the density of Aedes aegypti mosquitos, which also carry yellow fever, is increasing.

At the same time, the rise in temperatures caused by global warming is shortening the virus’ incubation period in the mosquito, which is capable of transmitting dengue 10 to 15 days after stinging an infected person.

Climate change is caused by emissions of greenhouse gases, principally carbon dioxide, which are produced by the burning of fossil fuels like oil, coal and natural gas and build up in the atmosphere, keeping the sun’s heat from escaping.

“Climate change favours the spread of the virus, but it is not the main element explaining the current outbreaks of the disease,” said Guzmán, who heads the research team that is working on a dengue vaccine.

Guzmán said that today, the main factors in the spread of dengue were people’s living conditions, increased global flows of people, and the lack of sustainable public health efforts in many countries.

“You can go around the world today in less than 24 hours, thanks to the high level of development of the means of transport, which facilitates the transmission and expansion of the four types of dengue virus,” she pointed out.

She also stressed that a country could make little progress fighting the disease if its neighbours were not also applying strict control measures. “This is much more complicated in countries with borders over which the flow of people is constant and heavy,” she added.

“Until a vaccine is developed, ongoing efforts to control dengue and its carrier, the mosquito, are indispensable. For now, there is no other alternative,” she underlined.

Guzmán said a sustainable programme must include environmental, clinical and entomological controls involving many of the country’s institutions, which means “the state’s determination to fight the disease is fundamental.”

The first epidemics of dengue fever were reported simultaneously in 1779-1780 in Asia, Africa, and the Americas.

But in the Americas, the disease was virtually eradicated by efforts to eliminate yellow fever, which is transmitted by the same mosquito. However, major outbreaks occurred once again in the 1960s in tropical areas in the region, and dengue is now making inroads in subtropical areas as well.

The first symptoms of the disease are flu-like – fever, headache, loss of appetite and joint and stomach pain – which stands in the way of early diagnosis, essential to providing the necessary supportive treatment in the form of rest, abundant fluids, pain-killers and hospitalisation if hemorrhagic fever or dengue shock syndrome develop.

Dengue has a short incubation period, usually less than a week. The symptoms include a sudden, rapidly climbing fever, severe headache, nausea and vomiting, loss of appetite, rash, and deep muscle and joint pains. The disease has been dubbed “breakbone fever” due to the last two symptoms.

If hemorrhagic fever develops, the patient starts bleeding – from the nose, the mouth, the gums, the skin, the intestinal tract. And when shock syndrome occurs, blood pressure plunges.

Hemorrhagic dengue, the most virulent form of the disease, killed 158 people – including 101 children – in Cuba in 1981, and claimed 74 lives in Venezuela in 1989.

World Health Organisation (WHO) experts have warned that 2002 will be a particularly negative year in terms of the spread of dengue, even worse than 1998, when an epidemic broke out in virtually all of the world’s tropical areas.

In 1998, 1.2 million cases were registered worldwide. Epidemiologists say this year’s total could be much higher, as many as 15 million cases.

“Until a vaccine appears, it is indispensable to put into practice ongoing programmes aimed at controlling dengue and the mosquito which transmits it. For now, there is no other option but prevention,” Guzmán underscored.

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