Chikungunya Transmission
Chikungunya is transmitted primarily through the bite of infected Aedes aegypti and Aedes albopictus mosquitoes, with additional routes including mother-to-fetus transmission during pregnancy, sexual transmission, blood transfusions, and laboratory exposure. 1, 2
Primary Transmission Route: Mosquito Vectors
The principal vectors are Aedes aegypti and Aedes albopictus mosquitoes, which acquire the virus by feeding on infected humans or nonhuman primates and subsequently transmit it to naive hosts. 1, 3
Female mosquitoes are the primary vectors that transmit the virus through their bite during blood feeding. 3
Vertical transmission among mosquitoes has been documented, meaning infected female mosquitoes can pass the virus to their offspring, contributing to sustained transmission cycles in endemic areas. 3
Transmission Cycles
Chikungunya virus maintains two distinct transmission patterns:
Enzootic sylvatic cycle: Involves transmission between nonhuman primates and forest-dwelling mosquitoes, similar to yellow fever's jungle cycle. 1
Urban cycle: Involves human-to-mosquito-to-human transmission, primarily through Aedes aegypti in populated areas. 1
Alternative Transmission Routes
Beyond mosquito bites, several other transmission pathways exist:
Perinatal transmission occurs when maternal viremia is present at the time of delivery, posing significant risk to neonates with potential for severe neurological complications including encephalopathy. 4, 5
Sexual transmission can occur between partners, even when the infected individual is asymptomatic. 6
Blood transfusion represents a theoretical but documented route of transmission during periods of viremia. 6
Laboratory exposure through needlestick injuries or other occupational exposures has been confirmed. 6
Clinical Timing of Infectiousness
The incubation period ranges from 1-12 days, with a median of 2-3 days after mosquito bite. 7, 5
Infected humans develop viremia that makes them infectious to mosquitoes, perpetuating the transmission cycle in areas where competent vectors are present. 1
Geographic Spread Considerations
CHIKV has now spread to more than 100 countries worldwide, with local mosquito-borne transmission documented in previously unaffected regions. 5
The virus demonstrates genetic variability with mutations (such as E1: A226V and E1: K211E) that may enhance transmission efficiency through different mosquito species, contributing to geographic expansion. 3