Epidemiology of Respiratory Infections during the COVID-19 Pandemic

Abstract

To face the COVID-19 outbreak, a wide range of non-pharmaceutical interventions (NPIs) aimed at limiting the spread of the virus in communities, such as mask-wearing, hand hygiene, social distancing, travel restrictions, and school closures, were introduced in most countries. Thereafter, a significant reduction of new asymptomatic and symptomatic COVID-19 cases occurred, although there were differences between countries according to the type and duration of the NPIs. In addition, the COVID-19 pandemic has been accompanied by significant variations in the global incidence of diseases due to the most common non-SARS-CoV-2 respiratory viruses and some bacteria. In this narrative review, the epidemiology of the most common non-SARS-CoV-2 respiratory infections during the COVID-19 pandemic is detailed. Moreover, factors that could have had a role in modifying the traditional circulation of respiratory pathogens are discussed. A literature analysis shows that NPIs were the most important cause of the general reduction in the incidence of influenza and respiratory syncytial virus infection in the first year of the pandemic, although the different sensitivity of each virus to NPIs, the type and duration of measures used, as well as the interference among viruses may have played a role in modulating viral circulation. Reasons for the increase in the incidences of Streptococcus pneumoniae and group A Streptococcus infections seem strictly linked to immunity debt and the role played by NPIs in reducing viral infections and limiting bacterial superimposed infections. These results highlight the importance of NPIs during pandemics, the need to monitor the circulation of infectious agents that cause diseases similar to those caused by pandemic agents, and the need to make efforts to improve coverage with available vaccines.

Time trend of respiratory viruses before and during the COVID‐19 pandemic in severe acute respiratory virus infection in the Sultanate of Oman between 2017 and 2022

“…In 2022, the prevalence of respiratory pathogens has rebounded to 43% in SARI cases, an increase of 325% compared to 2021, and slightly higher than pre‐COVID‐19 restrictions. This has been driven largely by an increase in the prevalence of influenza, RSV and human rhinovirus, which will be investigated further in the next section, but may indicate that a reduction in humoral and herd immunity to respiratory pathogens due to the low numbers of infection in previous years, as has been observed in other countries 13 …”

Human Parainfluenza Virus (HPIV) Detection in Hospitalized Children with Acute Respiratory Tract Infection in the Western Cape, South Africa during 2014–2022 Reveals a Shift in Dominance of HPIV 3 and 4 Infections

“…In contrast to HPIV, adenovirus, rhinovirus and RSV had continued to be present in the diagnostic samples throughout the restriction period, although pre-pandemic levels and expected seasonal periods of activity of these viruses were affected and only returned to pre-pandemic levels during 2022 (Figures 5 and S1). This resistance to NPI measures of especially non-enveloped viruses during the COVID-19 pandemic has been well documented [25,26] and also probably reflects the less than optimal control that was achievable during this time in communities using the public sector health (and other) services in South Africa. Lower than normal respiratory virus detection in clinical samples could also reflect the fact that access to healthcare services was more difficult during lockdowns and only very sick patients might have made it to hospital.…”

The association of COVID-19 pandemic with the increase of sinogenic and otogenic intracranial infections in children: a 10-year retrospective comparative single-center study

“…The associated reduced circulation of microbial agents and reduced vaccine uptake probably induced an “immunity debt,” resulting in a growing proportion of susceptible individuals [ 8 ]. There have been increases in the incidences of Streptococcus pneumoniae and invasive group A strep (iGAS) infections, likely due to the role of Non-pharmaceutical interventions (NPIs) in reducing viral infections and limiting bacterial superimposed infections [ 22 ]. Poor exposure to S. pneumoniae and iGAS due to NPI implementation may have led to a significant immunity debt in relevant population groups, now favoring infection development.…”