Data Analysis
Two one-year periods, October 2017 to September 2018 (year 1) and October 2018 to September 2019 (year 2), were studied to assess seasonal differences in population-based incidence and clinical burden for the respiratory viruses detected. To calculate population-based incidence per 100,000 persons for each virus, the number of adults with a laboratory-confirmed respiratory virus was divided by the adjusted 2010 U.S. Census population estimate for the catchment area. Population-based incidence and 95% confidence intervals were calculated overall and for four age strata: 18-49, 50-64, 65-79, and > 80 years of age [9]. If more than one virus was detected in a single specimen, each virus contributed to the respective incidence calculation. The population estimate was adjusted by the hospitals’ percent market share for zip codes as determined by the New York Statewide Planning and Research Cooperative System (SPARCS) [10]. To improve the incidence estimate’s reliability, the catchment area was defined as the eight zip codes in which the hospitals had> 60% market share (10032, 10033, 10034, 10040, 10452, 10453, 10463, and 10471).
To assess the clinical burden of specific viruses, the following outcomes associated with each virus were determined: the median hospital LOS, the proportion of patients who had an ICU admission, the ICU LOS, and in-hospital all-cause mortality. Time spent in the emergency department prior to being admitted to an inpatient unit was included in LOS calculations. If more than one virus was detected in a single specimen, each virus contributed to the respective median LOS, ICU admission and ICU LOS, and in-hospital mortality which was determined from recorded death notes in the EHR. Two sample tests of proportions were used to compare outcomes (ICU admissions and mortality) between each virus and all others (e.g., adenovirus vs. all other viruses). Median hospital LOS and median ICU LOS were compared using the Mann-Whitney test for each virus vs. all others.
The population-based incidence and clinical burden of influenza viruses (combined A H1, A H3, and B) were compared with those of non-influenza viruses (combined CoV229E, CoVHKU1, CoVNL63, CoVOC43, PIV types 1-4, RSV, hMPV, and AV) using the two sample test of proportions. RV/EV were excluded from the comparative analyses of the burden of influenza vs. non-influenza viruses. Patients with co-detections of influenza and non-influenza viruses were excluded from these comparative analyses.