Table 1.
Nosocomial Influenza A Virus, Influenza B Virus, and Respiratory Syncytial Virus Before and During the COVID-19 Era
| Variable | 2017–2019 (Feb–Apr) | 2020 (Feb–Apr)a | P Value |
|---|---|---|---|
| Laboratory request for respiratory viruses detectionb | |||
| Total no. of patients tested per mo, mean ± SD | 1,357 ± 188 | 1,342 ± 355 | .923 |
| No. of patients tested per mo (NPA or NPS collected >48 h of admission), mean ± SD | 110 ± 13 | 68 ± 16 | .001 |
| Influenza A virusc,d | |||
| Nosocomial (NPA or NPS collected >48 h of admission) | |||
| No. of positive per month, mean ± SD | 5 ± 2.7 | 0 ± 0 | .012 |
| No. of positive per 1,000 patient days per month, mean ± SD | 0.07 ± 0.05 | 0 ± 0 | .023 |
| Influenza B virusc,d | |||
| Nosocomial (NPA or NPS collected >48 h of admission) | |||
| No. of positive per month, mean ± SD | 2 ± 3 | 0 ± 0 | .386 |
| No. of positive per 1,000 patient days per month, mean ± SD | 0.03 ± 0.05 | 0 ± 0 | .403 |
| Respiratory syncytial virusc,d | |||
| Nosocomial (NPA or NPS collected >48 h of admission) | |||
| No. of positive per month, mean ± SD | 3 ± 2 | 0 ± 0 | .014 |
| No. of positive per 1,000 patient days per month, mean ± SD | 0.04 ± 0.02 | 0 ± 0 | .023 |
Note. NPA, nasopharyngeal aspirate; NPS, nasopharyngeal swab; SD, standard deviation; HCW, healthcare worker.
We monitored the incidence of nosocomial acquisition of influenza A, influenza B, and RSV from February 2020 to April 2020, after enforcement of universal masking in the hospitals on January 25, 2020. This period should be within the common seasonal influenza surge in Hong Kong in January–April and July–August, while RSV infection occurs throughout the year in Hong Kong.
Laboratory request for respiratory viruses detection among HCWs who attended staff clinic for the presence of respiratory symptoms is not included in Table 1. Of 16 HCWs tested for respiratory viruses, 14 were tested in the preintervention period and 2 were tested in the study period. In the preintervention period, influenza A and influenza B were diagnosed in 4 and 3 HCWs, respectively. In the study period, no HCW was positive for influenza A, influenza B, or respiratory syncytial virus.
The monthly breakdown number of nosocomial influenza A, influenza B, and respiratory syncytial virus per year, as well as the patient days are presented in Supplementary File 2 (online).
No one was COVID-19 positive in the study period, Feb–Apr 2020.