COVID‐19 and influenza testing in New York City

Abstract

Of the 6079 patients admitted due to coronavirus disease 2019 (COVID-19) during March 2020 to May 2020, 902 patients (14.8%) had influenza test. Among them, only three patients (0.33%) had positive test of influenza with concomitant infection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Our study demonstrated the very low rate of positive influenza test during COVID-19 pandemic. COVID-19 caused by a novel coronavirus, SARS-CoV-2, has spread all around the world since the first reported case in December 2019.1 New York City saw the number of confirmed COVID-19 cases rise at an astounding rate, with its first known case on 29 February 2020 and first confirmed death on 14 March 2020. Since then, the total number of deaths has risen exponentially to 12,895, with 172,354 patients suffering from COVID-19 as of 2 May in New York City.2 Initially, physicians tried to check concomitant influenza virus infection due to its similar presentation with COVID-193; however, we observed that most of the physicians discontinued influenza test through their experiences. The aim of this study was to investigate the rates of concomitant infection of influenza virus with SARS-CoV-2 during pandemic. This retrospective study was conducted using the medical records of hospitalized patients due to COVID-19, in the Mount Sinai Health System, with laboratory confirmed SARS-CoV-2 with polymerase chain reaction test. Patients' electronic medical records were reviewed and demographics, clinical course, comorbidities, and clinical outcomes were collected. Patients were categorized into two groups, those who had influenza test, and those who had not. Influenza test was conducted with polymerase chain reaction test. Differences in baseline characteristics between groups were evaluated using the χ2 test for categorical variables. Continuous variables are presented as mean ± standard deviation or median [interquartile range] depending on what is appropriate for the data distribution, and categorical variables were expressed as percentages. All vital signs were recorded at time of admission. All statistical calculations and analyses were performed on R (version 3.6.2, R Foundation for Statistical Computing) and OpenMetaAnalyst version 12.11.14 (available from http://www.cebm.brown.edu/openmeta/), with p < .05 considered statistically significant. This study was approved by the institutional review boards with waiver of patients' informed consent (#2000495). Of the 6079 patients admitted due to COVID-19 during 10 March 2020 and 7 May 2020, 902 patients (14.8%) had influenza test and 5175 patients (85.2%) had not. Figure 1 showed the trend of numbers of COVID-19 with or without influenza test, which revealed earlier peak in influenza test. Baseline characteristics are shown in Table 1. There were significant differences between age, sex, smoking, asthma, obstructive sleep apnea, human immunodeficiency virus, cancer between two groups. In-hospital mortality were similar in both groups (with or without influenza test: 24.2% vs. 24.3%, p = 1.00). Notably, of 902 patients with influenza test, only 3 patients (0.33% [95% confidential interval: 0.0%–0.7%]) had positive test of influenza with concomitant infection of COVID-19 and one out of these 3 patients died during the admission (33.3%). Our study demonstrated the very low rate of positive influenza test among COVID-19 patients, during COVID-19 pandemic. Not performing influenza test for COVID-19 patients could have two potential benefits; (1) less burden to laboratory technicians; (2) less potential spread to medical workers when getting samples from patients with COVID-19. Initially, physicians tried to check concomitant influenza virus infection due to its similar presentation; however, they tended to discontinue influenza test through their experiences which was validated by our study, since almost all the patients did not have concomitant influenza virus infection between March 2020 and May 2020. Our study has a limitation that we recruited only patients with COVID-19, and we do know have information of all patients with influenza test positive during study period. Nonetheless, this decision making could be generalizable during COVID-19 pandemic. Mai Takahashi, Natalia N. Egorova, Toshiki Kuno had full access to all the data in the study and takes responsibility for the integrity of the data and accuracy of the data analysis. Study concept and design: Toshiki Kuno. Data curation: Mai Takahashi and Natalia N. Egorova. Acquisition, analysis, or interpretation of data: Mai Takahashi, Natalia N. Egorova, and Toshiki Kuno. Drafting of the manuscript: Toshiki Kuno. Critical revision of the manuscript for important intellectual content: Mai Takahashi, Natalia N. Egorova, and Toshiki Kuno. Statistical analysis: Mai Takahashi. Administrative, technical, or material support: Natalia N. Egorova and Toshiki Kuno. Study supervision: Natalia N. Egorova and Toshiki Kuno.

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