CAP1 and severe acute respiratory syndrome: Coronaviruses, including severe acute respiratory syndrome–CoV and the newly emerged severe acute respiratory syndrome–CoV-2, and mosquito-borne flaviviruses, including dengue virus and Zika virus (ZIKV), encode viral 2′-O-methyltransferases to produce cap1 viral mRNAs (2), which effectively mimic those of the host to avoid immune surveillance.