OAS1 and dengue disease: Dengue virus infection causes the early induction of OAS1, whereas OAS2 and OAS3 are upregulated later.20, 21 Studies of polymorphisms in the Oas genes have emphasized the importance of all the three Oas genes during dengue virus infection.22 In the case of Chikungunya virus (CHIKV), OAS3 shows a strong correlation with resistance to CHIKV infection.