Comparison of viral respiratory pathogens circulation among Iranian pilgrims during two large religious mass gatherings: the Hajj and Arbaeen walk 2025

The Hajj and Arbaeen walk pilgrimages are significant religious mass gatherings (MGs) among Muslims. Respiratory tract infections (RTIs) remain a major concern during such events. This study aimed to evaluate the prevalence of respiratory viral infections among Iranian pilgrims during the 2025 Hajj and Arbaeen walk. Throat swabs were collected from 110 symptomatic Iranian pilgrims returning from these MGs. Molecular techniques were used to detect respiratory viruses. A total of 60 Hajj pilgrims and 50 Arbaeen walk pilgrims, with an age range 8 to 82 years for the combined groups, participated. Rhinovirus was the most common virus detected among symptomatic pilgrims in both MGs. Notably, the rate of SARS-CoV-2 infection was 1.7% in Hajj pilgrims and 32% in Arbaeen pilgrims. Co-infections of rhinovirus and SARS-CoV-2 were identified in 8% of Arbaeen pilgrims. Additionally, coronavirus OC43/HKU1, influenza A (H3N2), and influenza B virus were detected at low frequencies. No cases of MERS-CoV were found among the 2025 Hajj pilgrims. These findings provide preliminary data on the circulation of respiratory viruses during religious MGs in 2025. Continued surveillance is essential to reduce respiratory infection risks during such mass gatherings.