The Hajj is the oldest and largest annual mass gathering in the world and may increase the risk of spreading respiratory viruses.

Methods. We performed a prospective survey among a cohort of pilgrims departing from Marseille, France, to Mecca in the Kingdom of Saudi Arabia (KSA) for the 2012 Hajj season. Nasal swabs were collected from participants and tested for 11 respiratory viruses by real-time RT-PCR (rRT-PCR).

Results. Of 165 participants sampled before departing to the KSA, eight (4.8%) were positive for at least one virus (five rhinovirus, one influenza C, one adenovirus, and one enterovirus). Seventy symptomatic pilgrims underwent additional nasal swabs during their pilgrimage in the KSA, of which 27 (38.6%) were positive for at least one virus (19 rhinovirus, six influenza A, one influenza C, one respiratory syncytial virus B, one metapneumovirus, one adenovirus, and one enterovirus). This was significantly higher than the 4.8% who were positive before departing for the KSA (P<.001). Of 154 pilgrims sampled before leaving the KSA, 17 (11%) were positive for at least one virus (13 rhinovirus, three adenovirus, two influenza B, and one enterovirus), which was also significantly higher than the percentage of positive pilgrims (4.8%), before departing for the KSA (P=.040).

Conclusions. This study suggests a rapid acquisition of respiratory viruses among pilgrims during their stay in the KSA, most notably rhinovirus, and highlights the potential of spreading these infections in the pilgrims' home countries upon their return.