evidence: By going from disease (Barrett's esophagus) to molecule (ACE2) to cells (in vitro experiments) and back to clinical findings (COVID-19 patients), we showed that pH may have a great influence on SARS-CoV-2 infection and COVID-19 severity. Additional studies should be performed to not only confirm the clinical findings on a larger scale but also to assess the molecular mechanism related to pH-induced ACE2 expression. [...] Keywords: COVID-19, pH, SARS-CoV-2, proton pump inhibitors, Barrett's esophagus Citation: Jimenez L, Campos Codo A, Sampaio VdS, Oliveira AER, Ferreira LKK, Davanzo GG, Brito Monteiro Ld, Victor Virgilio-da-Silva J, Borba MGS, Fabiano de Souza G, Zini N, Andrade Gandolfi Fd, Muraro SP, Luiz Proença-Modena J, Val FA, Cardoso Melo G, Monteiro WM, Nogueira ML, Lacerda MVG, Moraes-Vieira PM and Nakaya HI (2021) Acid pH Increases SARS-CoV-2 Infection and the Risk of Death by COVID-19. Front. Med. 8:637885. doi: 10.3389/fmed.2021.637885