Dengue Fever

Dengue fever (DF) and its more serious counterpart, Dengue hemorrhagic fever (DHF), are quickly becoming a problem in more than the tropic regions where it has been most common.

A virus causes DF, and there are four main strains. Having been infected by one does not prevent contracting the others.

So, having endured a bout with one strain does not provide immunity against another illness from one of the other strains.

DF and DHF are spread primarily by the Aedes aegypti, or Asian Tiger, mosquito. Asian Tigers are aggressive day feeders that prefer humans as their main host. View a map of the Asian tiger mosquito’s habitat range.

Although dengue fever is mostly found in the tropics, it is beginning to be known as a significant disease in other areas. Dengue fever is not a newcomer to our planet. In Asia, Africa and North America, the first reported epidemics of DF were in 1779-1780. Often there were long periods of time, several decades, between outbreaks, because mosquitoes could only be carried on slow sailing ships.

Around 1950, a global pandemic occurred, beginning in Southeast Asia and by 1975, DHF had become the leading cause of death in children in the region. Spread of the disease has expanded rapidly in the last 15 years, including increasing reports of cases in the Americas. In fact, the CDC calls the emergence of DF and DHF in the Americas a “major public health problem.” Spraying efforts by public health organizations in the 1950’s and 1960’s significantly reduced Aedes egypti populations, and the spread of this disease, but were abandoned in the United States in the 1970’s. Now the populations of this mosquito are higher than before spraying was conducted.

By 1997, DF/DHF were considered to pose the greatest threat of mosquito borne diseases, rivaling malaria, worldwide. Serious mosquito eradication efforts are imperative, on both a global and community level.

Even the “milder” form of dengue fever is anything but mild. The symptoms are muscular and joint pain, high fever, severe headaches and backaches, vomiting, nausea and eye pain. DHF involves a high fever of extended duration, about 2-7 days. The initial symptoms are like those of many types of flu: headache, nausea, vomiting and abdominal pain. Then small capillaries begin to leak and hemorrhaging can occur through the skin, nose, gums and even internally. Without proper medical management, the hemorrhagic phase may lead to shock, failure of the circulatory system and possibly death.

There is no specific treatment for this fever, other than pain relievers, but aspirin should be avoided because it impairs blood clotting. In DHF, hospitalization is often required to insure proper fluid replacement.

Although dengue fever occurs mostly in tropical area infested with the Aedes aegypti or Aedes albopictus mosquitoes, it may be spread to other areas by travelers carrying the infection. In fact, one strain was found in Central America in 1994 and has spread into several countries in that region. Unfortunately, because the strain had not been present in the area for two decades, immunity in the area is low, and the disease is expected to spread quickly. All of the strains are found the Americas at this time.

No vaccines exist for any of the strains, and prevention is the best cure. Keep standing water clean, or eliminate it. And, avoid being bitten. Be sure all portals in buildings, such as houses, and offices are screened.

Community and governmental efforts to prevent mosquito breeding is essential, through use of natural predators like Bti and copepods. In terms of frequency of reported cases, the Center for Disease Control(CDC) reports there are approximately 50 to 100 million cases per year of DF. DHF infects approximately several hundred thousand people each year. The average rate of fatality for dengue hemorrhagic fever is about 5%. In the Americas in the late 1990’s there were approximately 250,000 cases of dengue fever, and about 7,000 reported cases of dengue hemorrhagic fever. By CDC estimates, between 100-200 cases of this virus are introduced into the United States each year by travelers.

Unfortunately, epidemics of the disease are occurring with increasing frequency and are more widespread than in the past. The CDC draws a parallel in dengue fever’s evolution in the Americas, calling it similar to the pattern of its spread to what occurred in South East Asia in the 1950’s and 1960’s.

As our global community becomes more urban, and we continue to become more mobile, the disease is expected to spread rapidly. And, education of medical personnel in the Americas is critical. At the present time the hemorrhagic disease is often poorly understood because it has not been a common ailment.