What causes Chikungunya fever?
Chikungunya disease is a viral disease transmitted in humans by the bite of infected mosquitoes. Aedes aegypti mosquito (also called yellow fever mosquito) is the primary transmission agent for Chikungunya Virus (CHIKV). This is usually found in tropics and hence the reason why Chikungunya is predominantly seen in asian countries. In recent cases, another mosquito species named Aedes albopictus is found to be a carrier. Aedes aegypti bites during day time and hence day time mosquito bite is the main reason for transmission.
Over years Aedes mosquito has evolved and has adapted itself for effective biting of humans! They even reduce humming of wings while approaching humans. They attack from below so there is minimal detection. This mosquito was usually seen in urban areas, but recently it has spread to many rural areas also. Aedes mosquito needs only 2ml of water for breeding and their eggs can lay dormant upto 1 year! Carrier mosquitos can even pass the infection to its next generation!
Chikungunya virus is a heat sensitive RNA virus (family is Togaviridae and genus is alphavirus - Group IV+). There are three major groups of these viruses namely west african, central african and asian.
Chikungunya virus requires an agent for transmission and hence direct human to human transmission is not possible. So far no such incidence is reported. Usually transmission occurs when a mosquito bites an infected person and then later bites a non infected person. Chikungunya also affects monkeys and it is also suspected that they are a major reservoir for the virus in africa.
Global distribution of Aedes Aegypti mosquito which causes Chikungunya
Yellow areas indicate the distribution of the aedes aegypti mosquito and red area indicates dengue infection activity.