Dengue fever

Dengue fever is the world’s most prolific mosquito-borne viral illness. Symptoms include high fever, headache, extreme pain and weakness in the muscles and joints, vomiting and a skin rash and can appear between 3 and 14 days after infection. While the disease is often mild and self-limiting, these symptoms may be excruciating and incapacitating. In severe cases, known as dengue shock syndrome or dengue haemorrhagic fever (DHF), patients can experience bleeding and extremely low blood pressure.  The fatality rate, although not very high, is on the increase.

Dengue fever is commonly spread by urban mosquitoes of the Aedes genus, and one of the most common vectors, Aedes aegypti, lives in close proximity to humans. Increases in prevalence are believed to be related to increasing urbanization and other social factors that favour increased mosquito reproduction.

The name denga is Swahili.

Demographic changes, in particular rapid, unplanned urbanization, have resulted in conditions that encourage the spread of diseases such as dengue fever. The two primary mosquito vectors of the dengue, Aedes aegypti and Aedes albopictus, have adapted from their natural forest environments, where they breed in tree holes containing rainwater, to the urban environment where they breed in drains, water cans, discarded tyres, pots and bottles (Gubler and Clark 1994).

In 2015, the Philippines became the first Asian country to approve the first dengue vaccine, Dengvaxia. The Philippine Department of Health launched a campaign to introduce the vaccine, during which over 700,000 people received at least one dose. The drug was approved for children aged 9 or older. In late 2017, the vaccination program was suspended due to concerns that the vaccine was making the disease worse in some cases. A few days later, the manufacturer, Sanofi, released a statement reporting concerns that the vaccine could make dengue infection worse in recipients who had not had the disease before. They categorically denied using the Filipino population as “guinea pigs” to test their vaccine.  The Philippine Department of Justice indicted officials from both Sanofi and the Philippine Health Department.  The DOJ said that at least 10 deaths had been linked to Dengvaxia, even though Sanofi insisted that it was “safe and effective.”

Dengue fever is distributed throughout the tropical and subtropical areas of the globe and has been reported in over 100 countries; worldwide, there may be up to 2 billion people at risk. All four of the dengue virus serotypes are circulating in Asia, Africa, and the Americas. They are cousins of the yellow fever microbe.

The disease infects an additional 30 million to 60 million people each year. It may occur in any country where the mosquito carriers (mainly Aedes aegypti) breed. Outbreaks occur chiefly in Africa, India, the Far East, and also in Hawaii, the Philippines and Caribbean Islands, reaching a peak during the rainy season. Cases are found mainly in cities and towns, although there is a rise in the number of reported cases in rural areas. 90% of the victims are under 5 years of age.

A marked increase in cases of dengue fever has been observed over recent decades, especially in tropical and subtropical areas of Central and South America and the Caribbean. This increased activity has recently been associated with the re-emergence of one type of the virus that has not been observed in Central America for some time.