CHIKV-induced joint disease is driven by CD4+ T cells [3,12,72], and neurological infection with a more neurovirulent CHIKV strain has been associated with more CD4+ T cells infiltrating the CNS compared to less neurovirulent CHIKV strains [70], suggesting a similar pathogenic mechanism occurs during CHIKV-induced neurological disease. Here, CD4 is linked to nervous system disorder.