Background: Hajj is a mass gathering undertaken annually in Mecca, Saudi Arabia. The 2009 Hajj coincided with both the pandemic influenza A/H1N1 2009 (A(H1N1)pdm09) and seasonal types of influenza A viruses. The interaction between pandemic influenza and Hajj could cause both a high level of mortality among the pilgrims and the spread of infection in their respective countries upon their return home.

Objective: The present study attempted to determine the point prevalence of A(H1N1)pdm09 among returning Iranian pilgrims, most of whom had been vaccinated for seasonal influenza but not A(H1N1)pdm09.

Methods: Pharyngeal swabs were collected from 305 pilgrims arriving at the airport in Shiraz, Iran. RNA was extracted from the samples and A(H1N1)pdm09 and other seasonal influenza A viruses were detected using TaqMan real-time PCR. For A(H1N1)pdm09-positive samples, the sensitivity to oseltamivir was also evaluated.

Results: Subjects included 132 (43.3%) men and 173 (56.7%) women, ranging in age from 24 to 65 years. The A(H1N1)pdm09 virus was detected in five (1.6%) pilgrims and other influenza A viruses in eight (2.6%). All the A(H1N1)pdm09 were sensitive to oseltamivir.

Conclusions: Only five cases were found to be positive for A(H1N1)pdm09, and it seems unlikely that the arrival of infected pilgrims to their homelands would cause an outbreak of a new wave of infection there. Thus, the low morbidity and mortality rates among the pilgrims could be attributed to the characteristics of A(H1N1)pdm09, which causes morbidity and mortality in a way similar to the seasonal influenza infections, absence of high-risk individuals among the Iranian pilgrims, and the instructions given to them about contact and hand hygiene, and respiratory etiquette.