Table 2.

Expected number of coinfections throughout the pandemic among patients at the Mayo Clinic with cotesting PCR data. In the first column, we show the total number of cases at the Mayo Clinic during the time period with PCR testing data available for both COVID-19 and influenza within +/− 14 days, including both positive and negative PCR tests. For each row, this total is used as the denominator to compute the percentages, which are displayed next to case counts. In the middle columns, we show the number of cases with positive PCR tests for COVID-19, influenza, and both COVID-19 and influenza, respectively. In the last column, we show the expected number of cases with positive PCR tests for both COVID-19 and influenza, assuming that the probabilities of testing positive for COVID-19 and influenza are independent in the general population (see Methods). Note that for the first two time periods, all confirmed coinfection cases had influenza diagnoses determined via ICD codes or clinical notes and not lab tests, so the coinfection case counts for these time periods were zero.

Time period	Cases with PCR testing for both COVID-19 and Flu within 14 days	COVID-19 positive tests case count (%)	Flu positive tests case count (%)	COVID-19 + Flu positive tests case count (%)	Expected number of COVID-19 + Flu positive tests case count (%) [95% CI]
2020 March 12 to 2021 March 15	14,320	1,162 (8.1%)	165 (1.2%)	0 (0.0%)	2.6 (0.02%)
[2.2 (0.02%), 3.0 (0.02%)]
2021 March 16 to 2021 June 15	1,806	42 (2.3%)	0 (0.0%)	0 (0.0%)	0.0 (0.0%)
[0.0 (0.0%), 0.0 (0.0%)]
2021 June 16 to 2021 December 13	28,946	3,918 (13.5%)	520 (1.8%)	9 (0.0%)	13.6 (0.05%)
[12.4 (0.04%), 14.8 (0.05%)]
2021 December 14 to 2022 April 2	57,488	13,740 (23.9%)	2,332 (4.1%)	94 (0.2%)	107.5 (0.19%)
[102.9 (0.18%), 112.0 (0.19%)]