What is Dengue Fever ?

The global incidence of dengue has grown dramatically in recent decades. The rising level of dengue infections has become a serious international concern.Each year, the World Health Organization reports that approximately 50 million people are infected with dengue and some researchers estimate that this number could be as high as 100 million. In Sri Lanka, from 1st January to 7^th July 2017, the Epidemiology Unit of the Ministry of Health (MoH) Sri Lanka reported 80, 732 dengue fever cases, including 215 deaths. Therefore, a growing concern regarding this issue in Sri Lanka can be identified.

According to world health organisation (WHO), dengue is a mosquito-borne viral infection. The infection causes flu-like illness, and occasionally develops into a potentially lethal complication called severe dengue. Moreover, about half of the world’s population is now at risk. Dengue is found in tropical and sub-tropical climates worldwide, mostly in urban and semi-urban areas. The viruses that cause dengue fever are spread by mosquitoes of the species Aedesaegypti, and sometimes also by Aedesalbopictus. The virus is transmitted to humans through the bites of infected female mosquitoes. Aedesaegypti is a day biting mosquito. That means that the mosquito is most active during daylight, for approximately two hours after sunrise and several hours before sunset. The life cycle of these mosquitoes are illustrated in the following figure. After virus incubation for 4 – 10 days, an infected mosquito is capable of transmitting the virus for the rest of its life. Infected symptomatic or asymptomatic humans are the main carriers and multipliers of the virus, serving as a source of the virus for uninfected mosquitoes. Patients who are already infected with the dengue virus can transmit the infection (for 4–5 days; maximum 12) through Aedesmosquitoes after their first symptoms appear.