Four different types of dengue viruses are responsible for dengue fever. One or more than one type of virus can enter into female Aedes mosquito while biting an infected person and when this mosquito bites other human, injects virus along with saliva. Recovery afer infection with one type of virus can produce lifelong immunity to the type but severe complications can occur on secondary infection by other serotype of virus.

The dengue virus multiplies in the body of the female Aedes mosquito. This virus does not harm mosquito. The Aedes mosquito is of black colour with white spots and stripes on its body. The female Aedes is responsible for the transmission of this disease from an infected person to a healthy person. In order to save oneself from this disease, it is very important that various preventive measures, including destruction of the breeding sites should be adopted. For this purpose it is very important to have a complete knowledge of the life cycle of the mosquito.

During it life cycle, the dengue mosquito passes through four distinct phases of development which are as follows:

Eggs

The female Aedes mosquito lays eggs in clean water. Even a very small quanity of this water is quite enough for this purpose (e.g., water utensils in which water is kept, vases or discarded items in which water can collect)

Larva

The eggs hatched into larvae after 2- 7 days. They breathe through siphon which protrude out of water. They feed on bacteria or other microorganisms. They move actively from top to the bottom. As they grow they change their skin for four times. Later they change to the next stage called Pupa.

Pupa

They live near the surface of water and breathe through small tubes present on the dorsal surface of the body. They do not feed.

Adult

After two days the skin of the dorsal surface of pupa bursts and mosquito emerges out. After resting sometime, it flies away.