Mode of Transmission of Chikungunya
Chikungunya virus is transmitted primarily through the bite of infected Aedes aegypti and Aedes albopictus mosquitoes, with vertical (mother-to-child) transmission occurring less commonly during the peripartum period.
Primary Vector-Borne Transmission
The dominant transmission route is through mosquito vectors 1, 2, 3, 4:
- Aedes aegypti is the most frequently detected and confirmed vector, testing positive for CHIKV in 22 of 29 field studies 4
- Aedes albopictus serves as a secondary but important vector, confirmed positive in 9 of 12 field studies 4
- Both species demonstrate high laboratory vector competence, with mean transmission efficiencies of approximately 37% for Ae. aegypti and 47% for Ae. albopictus 4
Regional Vector Considerations
Other Aedes species may have regional relevance but require further validation, including Aedes vittatus, Aedes polynesiensis, Aedes koreicus, and Aedes japonicus 4. While CHIKV RNA has been detected in Culex quinquefasciatus, Psorophora spp., and Wyeomyia spp. in field studies, laboratory evidence does not support these as competent vectors 4.
Vertical (Mother-to-Child) Transmission
Vertical transmission represents a clinically significant but less common route 5, 6:
- Occurs most frequently intrapartum when maternal viremia is present at the time of delivery 5
- Approximately 50% of neonates with symptomatic CHIKV infection will develop neurodevelopmental delay 6
- Infected neonates may present with encephalopathy, high morbidity, and clinical sepsis in the first days of life 5, 6
- Viral antigens can be detected in placental tissue, including Hofbauer cells, accompanied by pro-inflammatory responses 5
Critical Clinical Pitfall
Pregnant women infected near delivery pose the highest risk for vertical transmission. Unlike the relatively mild course in pregnant women (who appear protected from severe joint pain), perinatally infected neonates experience severe outcomes including encephalopathy and potentially fatal complications 5.
No Evidence for Other Transmission Routes
There is no documented evidence for:
- Direct person-to-person transmission (non-vector)
- Transmission through blood transfusion (though theoretically possible during viremia)
- Sexual transmission
- Airborne transmission
The expansion of Aedes mosquito habitats driven by climate change, urbanization, and global travel continues to increase the geographic risk for chikungunya transmission 1, 2, 3.