Controlling COVID-19 also suppresses other respiratory infections

Public health measures taken to curb the spread of the novel coronavirus disease (COVID-19), particularly the wearing of face masks, may also be suppressing other respiratory viral infections (RVIs) among elderly adults, according to a recent Singapore study.

“The significant and sustained decrease in incidence of hospitalizations due to RVIs among older Singaporeans suggests that the role of simple preventive measures, such as the wearing of face masks, deserves further study in the postpandemic era, given the significant morbidity and mortality attributable to common RVIs in this vulnerable population,” the researchers said.

At the Singapore General Hospital, multiplex polymerase chain reaction (PCR) assays are used to diagnose RVIs in patients presenting with the relevant clinical features. The present study compared rates of PCR-positive community-onset RVI among hospitalized elderly adults (aged ≥65 years) between February 2020, during the pandemic, vs 2018–2019.

Measures to slow the pandemic also seemed to strongly affect other RVIs. Before COVID-19, there was an average of 80±27 monthly hospitalizations for community-onset RVI, which dropped to 18±18 cases per month during the pandemic (p<0.001). [J Am Geriatr Soc 2021;doi:10.1111/jgs.17179]

Notably, such a decrease occurred despite the increased testing and vigilance for respiratory symptoms.

Stratified analysis showed that in the prepandemic era, 858 of 94,369 admissions tested positive on PCR for community-onset influenza, yielding an incidence rate of 9.0 cases per 1,000 admissions. This rate dropped by nearly 90 percent during the pandemic, resulting in an incidence of 0.9 cases per 1,000 admissions (37 cases, 40,810 admissions).

The resulting difference was statistically significant (incidence rate ratio [IRR], 0.10, 95 percent confidence interval [CI], 0.07–0.134; p<0.001).

A similar trend was reported for PCR-proven noninfluenza RVIs. Before COVID-19, 12.2 cases per 1,000 hospitalizations would test positive. During the pandemic, following health protocols, cases of noninfluenza dropped to 4.2 per 1,000 admissions, leading to an IRR of 0.34 (95 percent CI, 0.29–0.49; p<0.001).

“The COVID-19 pandemic provided a unique opportunity to observe the potential secondary impact of public health measures on the incidence of hospitalizations due to common RVIs among older Singaporeans” because these measures were introduced and relaxed in phases, the researchers said.

As lockdowns and social distancing were eased, mask-wearing remained in place, allowing for a closer look at masks in particular.

“The decrease in hospitalizations for common RVIs among older adults remained with no rebound in admissions,” they said. “Advocating mask-wearing may thus be an effective and simple way to reduce community-based transmission of common RVIs, especially among the vulnerable older population.”

Nevertheless, the researchers conceded that important confounders were left unaddressed in the analysis, including seasonal variations in RVIs and the increase in influenza vaccination due to public health campaigns during the pandemic. Future studies should take these into consideration.