According to a study published in The Journal of Infectious Diseases, the COVID-19 virus interrupted seasonal patterns of respiratory illnesses, but the incidence of the rhinovirus swiftly returned to historical levels and exceeded that of SARS-CoV-2 during the first 2 years of the pandemic.

The authors wrote, “Viral respiratory illnesses are the most common acute illnesses experienced and generally follow a predicted pattern over time. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic interrupted that pattern.”

The researchers evaluated viral respiratory patterns by utilizing data from the Household Influenza Vaccine Evaluation (HIVE) study established in 2010, which was designed to examine the preventive effects of influenza vaccination.

The goals of the HIVE study progressively expanded to gain a greater understanding of other common respiratory pathogens, including SARS-CoV-2.

Between 2015 and 2022, individuals from households in Southeastern Michigan that participated in the HIVE study were examined annually to detect variations in virus-specific incidence, characteristics, and seasonality before the pandemic (2015–2020) compared with the COVID-19 pandemic (2021–2022).

The participants in the study were contacted weekly to check for acute respiratory infections (ARI). Those with at least two specified symptoms provided nasopharyngeal and throat samples for real-time polymerase chain reaction testing, which were self-collected during the pandemic. All illnesses were documented, and the frequency and percentage of ARIs and their causative agents were categorized by age groups (<5, 6-11, 12-17, 18-49, and ≥50 years). A latent class analysis was conducted to develop and assess potential syndromic profiles.

The results revealed that between 2015 and 2022, the HIVE study followed 1,755 participants over 7,785 person-years, documenting 7,833 illnesses. During the prepandemic period, rhinovirus was the most frequently identified illness, with the incidence decreasing with age (<5 years: 75.8; ≥50 years: 20.4 per 100 person-years). Common-cold human coronaviruses (HCoVs) followed a comparable pattern and were the second most frequently identified virus. Influenza A and B had consistent incidence across age groups, while the youngest age group had the highest rates of respiratory syncytial virus (RSV) and human parainfluenza virus (HPIV) documented as 12.7 and 14.1 per 100 person-years, respectively.

During the pandemic, rhinovirus remained the most common virus, with an incidence of 31.3 per 100 person-years. SARS-CoV-2 was more frequent than HCoVs but had comparable incidence rates (9.9 vs. 8.03 per 100 person-years).

Seasonality exhibited limited variation with regard to the annual incidence of most ARIs during the prepandemic time frame, but RSV, HPIV, and human metapneumovirus (HMPV) were virtually absent in the first pandemic year. Rhinovirus and HCoVs were most frequent in the second year, with a modest reoccurrence of influenza. The incidence of SARS-CoV-2 was low initially but remained less common than rhinovirus and somewhat more frequent than HCoVs in the second year.

Symptom profiles were not obviously distinct across viral infections. Latent class analysis revealed certain patterns such as influenza A/B and SARS-CoV-2 were in the congested myalgia cluster, while rhinovirus, HCoVs, RSV, HMPV, and HPIVs were in the upper respiratory congestion cluster. Lower respiratory congestion was the smallest cluster.

The authors concluded, “A great advantage of HIVE’s approach is the ability to examine all the major respiratory viruses simultaneously using the same methods. A clear goal currently will be to document how and when the pattern of infection with all the major respiratory viruses fully returns and the place of SARS-CoV-2 infection in personal patterns.”

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