September 09, 2010

"Dengue needs to be fought on a daily basis—we must never lower our guard."


Lucia Brum is MSF's technical advisor for emerging diseases.

Doctors Without Borders/Médecins Sans Frontières (MSF) is conducting an emergency response to a dengue outbreak in Tegucigalpa, the capital of Honduras. To find out more about what it involves, we spoke to Lucia Brum, MSF technical advisor for emerging diseases.

Does the increase in dengue fever outbreaks in Latin America mean there are insufficient resources to control the disease?

The fight against dengue requires a comprehensive, inter-related strategy, which includes epidemiological and entomological surveillance, community education, environmental sanitation, vector control (ie. controlling the mosquito that transmits the disease), and medical treatment. So the problem is not a lack of economic resources per se, but the absence of a comprehensive approach to the disease by public health programs in most Latin American countries. The health programs often lack continuity or fail to address all aspects of combating the disease.

There are also socioeconomic factors at play, including poor sanitation and problems with water supplies. For example, in the areas in Honduras where the MSF teams are working, residents only receive water once every two weeks, which means they have to store it. This increases the chances of dengue occurring, because the Aedes aegypti mosquito that passes on the disease breeds in stagnant water. When rubbish isn’t collected regularly, this can be a problem, too, since garbage can also harbor stagnant water.

What should we do to fight dengue?

Dengue needs to be fought on a daily basis—we must never lower our guard. Media attention tends to focus on major outbreaks of the disease, when there are large numbers of cases, but, as I mentioned earlier, there are a whole series of things we can do, all year round, first to prevent, and then to contain, the disease.

There is a tendency to lower our guard because, unlike other diseases, which tend to be stable all year round, dengue occurs in epidemic peaks. These generally coincide with warmer weather and the rainy season, usually during the second half of the year in Latin American countries.

During an epidemic, there is a tendency for government officials and the population at large to blame each other for what is happening. But, really, dengue prevention is the responsibility of everyone. On one hand, it depends on the state promoting community education that will encourage people to learn what they can do to protect themselves. On the other hand, people need to develop their own active prevention strategies. Without community participation, and as long as there is no effective vaccine, we will never be able to eradicate dengue.

Can you stop the transmission of dengue, and is research being done to find a drug or vaccine to protect against it?

Honduras 2010 © Juan Carlos Tomasi

An MSF staff performs vector control in an area Tegucigalpa. Teams are working to fumigate around 4,400 homes.

Until now, the only way to prevent dengue has been through vector control,  which means fighting the mosquito that transmits the disease. On a medical level, the majority of cases are treated syptomatically and as outpatients. Medical staff can alleviate the symptoms and try to avoid complications, but there is no etiological treatment for dengue, and there are no antiviral drugs specific to the disease.

The success of the treatment and a good prognosis are closely related to clinical assessment and keeping the patient well hydrated from early on. However, during dengue epidemics the high percentage of the population affected means that health services tend to become overcrowded, hindering the critical early clinical assessment. This then contributes to the development of severe cases (hemorragic dengue and dengue shock syndrome) and increasing mortality.

Twenty-six years ago, the World Health Organization formed a committee for the development of vaccines against dengue, with the aim of encouraging laboratories and research institutes to participate, but a vaccine is still not available on the market.

This lack of a vaccine can be attributed to several factors, but the main problem is that there are four different types of dengue virus—serotypes 1, 2, 3 and 4—so, to be effective, a vaccine must inhibit all four serotypes simultaneously.

There is an urgent need for a vaccine because it is expected that dengue will spread to other countries and epidemics will become even more numerous and severe. It is anticipated that a vaccine may become available in the next five years.

Why are there so many cases of dengue in Honduras at the moment?

The global emergence of dengue as a major viral disease transmitted by mosquitoes is closely related to the problems of modern society in less developed countries: demographic explosion, unplanned urbanization, the deterioration of public health programs, and environmental pollution, with plastics and tires serving as breeding grounds for mosquitoes. Globalization has also played its part, with the transfer of patients, vectors and viral serotypes to areas where there were no previous cases of dengue. Similarily, global warming has also contributed to the spread of the disease.

The situation in Honduras is part of a recent global trend: in Latin America, Asia, Africa, and Oceania epidemics have been increasing, with more cases of classic dengue fever, but also increased incidence of severe cases, both hemorrhagic dengue and dengue shock syndrome. These last two are the most dreaded forms of the disease, requiring hospital care as they are potentially life-threatening. Both are the focus of MSF’s medical intervention for children in the dengue pediatric ward of San Felipe Hospital in Tegucigalpa, as this is the age group that is most at risk, accounting for more than 70 percent of all reported deaths.

What is the impact of outbreaks on affected countries?

Honduras 2010 © Juan Carlos Tomasi

An MSF medical staff examines a child suspected of having dengue fever.

The main burden that dengue imposes on a country is the huge number of hospital admissions and the number of days that the illness lasts. Caring for a large number of dengue patients requires equipment, trained doctors and nurses, fast criteria for risk classification of patients, beds and materials, and establishing treatment and isolation guidelines. Isolation refers not only to the usual precautions for handling blood and other bodily fluids, but also to the use of mosquito nets. If mosquitoes of the Aedes type are present in the hospital wards and bite patients with viremia (the virus circulating in the blood during the febrile period), then the insects can transmit the infection, contributing to the spread of the epidemic.

The disease also generates indirect costs that are not usually taken into account but which have a substantial economic impact. There are the working days lost by the affected population: a patient needs an average of 10 days of rest before recovering—not for nothing is the disease known as the “bone-breaker fever”. Epidemics also overwhelm hospitals, and health systems are overstretched, disrupting the management and flow of patients with other diseases.

As I have said, it is vital to develop comprehensive strategies to combat the disease. With good guidance, access to health services and early clinical management, no one should die from dengue fever.