Frequency and Demographic Patterns of SARS-CoV-2 and Influenza Virus Infections in Khuzestan: A Retrospective...

To describe the frequency and demographic characteristics of SARS-CoV-2 and influenza infections, as well as their co-occurrence, among patients in Khuzestan province.

This retrospective laboratory-based study was conducted at the Reference Laboratory of Ahvaz Jundishapur University of Medical Sciences. Between March 2021 and November 2023, respiratory swab samples from patients with suspected Coronavirus disease 2019 (COVID-19) or influenza referred from 64 affiliated healthcare institutions (23 health centers and 41 hospitals) were tested for SARS-CoV-2 and influenza A/B using RT-qPCR. Demographic and laboratory data were analyzed using chi-square and simple logistic regression, and the results were expressed as odds ratios (ORs) with 95% confidence intervals (CIs).

A total of 148,079 respiratory specimens were analyzed between 2021 and 2023. Among them, 41.2% tested positive for SARS-CoV-2 in 2021, 14.9% in 2022, and 4.5% in 2023, showing a marked decline in COVID-19 positivity over time. In contrast, influenza positivity progressively increased from 13.3% in 2021 to 15.5% in 2022 and 20.8% in 2023, coinciding with broader testing coverage. Females consistently showed higher infection rates for both viruses. The most affected age groups for COVID-19 shifted from 40 to 50 years in 2021 to 20-30 years in 2022 and ≥ 70 years in 2023, while influenza was more frequent among individuals under 20 years in 2023. Coinfection with SARS-CoV-2 and influenza was uncommon, detected in only 0.6% of the patients in 2023, predominantly involving the H1N1 subtype.

The present study demonstrates a declining trend of SARS-CoV-2 infection alongside a progressive rise in influenza cases in southwest Iran from 2021 to 2023. The findings highlight age- and sex-related variations in infection patterns and underscore the value of continuous dual surveillance for both viruses.