Transmission Edit
Chikungunya is generally transmitted from mosquitoes to humans. Less common modes of transmission include vertical transmission, transmission from mother to child during pregnancy or at birth. Transmission via infected blood products and through organ donation is also theoretically possible during times of outbreak, though no cases have yet been documented.[13]
Chikungunya is related to mosquitoes, their environments, and human behavior. The adaptation of mosquitoes to the changing climate of North Africa around 5,000 years ago made them seek out environments where humans stored water. Human habitation and the mosquitoes’ environments were then very closely connected. During periods of epidemics humans are the reservoir of the virus. Because high amounts of virus are present in the blood in the beginning of acute infection, the virus can be spread from a viremic human, to a mosquito, and back to a human.[38] During other times, monkey, birds and other vertebrates have served as reservoirs.[39] Three genotypes of this virus have been described, each with a distinct genotype and antigenic character: West African, East/Central/South African, and Asian genotypes.[40]
Chikungunya is spread through bites from Aedes mosquitoes, and the species A. aegypti was identified as the most common vector, though the virus has recently been associated with many other species, including A. albopictus.[13] Research by the Pasteur Institute in Paris has suggested chikungunya virus strains in the 2005-2006 Reunion Island outbreak incurred a mutation that facilitated transmission by the Asian tiger mosquito (A. albopictus).[41] Other species potentially able to transmit the chikunguna virus include A. furcifer-taylori, A. africanus, and A. luteocephalus.[13]