Response to Letter Regarding "A Case Series of Patients Coinfected With Influenza and COVID-19".

To the Editor,

We want to sincerely appreciate Suwanwongse and Shabarek[1] for investing their precious time to read the article “A Case Series of Patients Coinfected With Influenza and COVID-19” with keen observation and giving an unbiased opinion. Suwanwongse and Shabarek also provided sound reasoning and cited appropriate literature backing up their point. We agree with Suwanwongse and Shabarek’s theoretical reasoning of influenza coinfection, worsening an inflammatory cascade. We also agree on the point of upregulation of interferons with viral infections like influenza[2] and the citing of literature related to interferon-driven upregulation of ACE2, which is the key receptor for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) to enter the human host cells.[3] The authors’ concern about the statement “the coinfection did not significantly worsen the symptoms or outcomes,” stating it is premature, is apt and justified from the points mentioned above. Finally, we agree with the authors’ comments until future studies show any surprising outcomes. The impact of coinfection of both influenza and COVID-19 (coronavirus disease-2019) on clinical outcomes is unknown at this point. Physicians should be mindful that a positive influenza test does not rule out the possibility of simultaneous COVID-19 disease and vice versa.