Given that IgM-based serological methods are widely used for chikungunya diagnosis, the findings that anti-CHIKV IgM can persist for long periods raise concerns regarding the correct interpretation of a positive IgM-based test, as it may represent a previous infection rather than an acute or recent infection, especially in settings where large CHIKV epidemics have occurred or endemic CHIKV transmission has been established. The gene discussed is CD40LG; the disease is infection.