WATCH: What is dengue fever?

MANILA, Philippines— The Department of Health this week declared a national dengue epidemic.

Dengue fever is the world’s most common mosquito-borne disease.

The virus is known to be transmitted through bites of the female aedis aegypti mosquito.

These mosquitoes are found in tropical and sub-tropical areas, predominantly in urban and semi-urban areas.

Dengue fever is a severe flu-like illness that affects infants, children and adults.

It contributes to 25,000 global deaths annually.

The World Health Organization said early detection and access to medical care can lower fatality rates.

There are four distinct but related viruses that cause dengue.

Studies said that recovery from dengue fever gives lifelong immunity to that particular strain while a second infection by one of the different strains can lead to dengue hemorrhagic fever.

Dengue hemorrhagic fever has a 2.5-percent mortality rate. —Information from WHO/CDC/EDC/Standford University/India Ministry of Health &Family; Video by AFP