"The prevalence of myocarditis among COVID-19 patients is unclear, partly because the early reports often lacked the specific diagnostic modalities to assess myocarditis. Some argued that up to 7% of COVID-19–related deaths were attributable to myocarditis.26 However, this was assumed and not based on confirmatory diagnoses of myocarditis and thus may be an overestimate. In contrast, many laboratories are rationing tests and are first screening for known pathogens resulting in flulike symptoms.
If a positive pathogen is identified, then testing for SARS-CoV-2 is not performed. This is erroneous and likely to miss the true frequency of SARS-CoV-2 infection because it assumes mutual exclusivity of SARS-CoV-2. One report identified 24.5% of COVID-19 patients as having coinfection with other viruses.27 Hence, it is possible that many cases of COVID-19–related myocarditis were missed due to a lack of SARS-CoV-2 diagnosis."
