Circulation of Influenza and Other Respiratory Viruses in Tunisia, 2022-2023 Season

Influenza sentinel surveillance has been ongoing in Tunisia since 1999. We describe the epidemiology of respiratory viruses during 2022-2023, the first season to include testing for other respiratory viruses, such as respiratory syncytial virus (RSV).

We analyzed weekly surveillance data from severe acute respiratory infection (SARI) inpatients and influenza-like illness outpatients from 11 hospitals and 85 clinics in Tunisia. Nasopharyngeal specimens and demographic, clinical, and vaccination data were collected. Specimens were tested by rRT-PCR for influenza, SARS-CoV-2, RSV, and 18 other respiratory viruses. Descriptive statistics were used to summarize case characteristics; group differences were assessed using chi-squared or Fisher's exact tests.

2038 specimens were collected from unique patients; 1231 (60.4%) were positive for ≥ 1 respiratory virus and 200 (16.2%) were positive for ≥ 2 viruses. Influenza was the most detected (n = 445; 21.8%), followed by rhinovirus (n = 301, 14.8%), RSV (n = 255, 12.5%), and SARS-CoV-2 (n = 125, 6.1%). Among SARI cases, infections with influenza and SARS-CoV-2 were more common in adults ≥ 50 years (61.8% and 71.4%, respectively), while children < 2 years had higher RSV prevalence (83.0%, adjusted p-value = 0.004). 4.9% of patients received a recent influenza vaccine.

The burden of respiratory viruses varied by age, with RSV being more prevalent among younger children and SARS-CoV-2 and influenza being more prevalent among older adults. Ongoing sentinel surveillance is essential to monitor priority respiratory pathogens, particularly those with available public health interventions, such as vaccination, to enable timely action and reduce disease burden.