Material and methods
Search strategy
The all published studies were searched using ISI, Science direct, Scopus, Pubmed, Google scholar, and Wiley online international databases from December 2019 to July 2021. The search strategy was done using the following key words: “co-infection”, “COVID-19 virus”, “Influenza”, “influenza virus”, “Human flu”, “SARS-COV-2”, “severe acute respiratory syndrome coronavirus 2”, “coronavirus disease 2019 virus”, “2019 novel coronavirus”. AND’/‘OR’ operators were used to identify the articles. For improving the quality of the present literature, the references of studies were examined. In addition, all titles and abstracts were randomly evaluated by two reviewers in order to confirmed all of the studies have inclusion criteria and their results were compared with each other.