Influenza a common viral infection among Hajj pilgrims: time for routine surveillance and vaccination.

BACKGROUND

The annual Hajj pilgrimage to Mecca, Saudi Arabia brings over two million people to a small confined area. Respiratory tract infection is the most common disease transmitted during this period. For most of the etiologic agents of upper respiratory tract infections, no vaccine or prophylaxis is available, except for influenza. Yearly influenza vaccination of high-risk groups is recommended, but no special recommendations are available for those performing the Hajj or other similar large congregational activities. Viral surveillance studies are being carried out through more than 100 centers around the world to identify newly emerging viruses. Saudi Arabia is not one of those centers and no routine surveillance takes place.

METHODS

Five hundred Hajj pilgrims presenting with upper respiratory tract symptoms from different parts of the world were screened by way of a throat swab for viral culture, including influenza A and B, parainfluenza, respiratory syncytial virus (RSV), adenovirus, herpes simplex virus (HSV), and enteroviruses. Information was collected on age, sex, nationality, smoking habits and upper respiratory tract symptoms. Vaccination status for influenza and meningococcus was obtained by self-declaration, since most pilgrims did not have their vaccination cards with them. Only those with symptoms including at least fever, reported by the patient to be >38.3 degrees C, and/or sore throat were included. Pilgrims with any other symptoms, especially myalgia and fatigue alone, were excluded, since many of the physical chores during the pilgrimage may contribute to such symptoms.

RESULTS

Fifty-four patients (10.8%) had positive viral throat cultures. Of these, 27 (50%) were influenza B, 13 (24.1%) were HSV, 7 (12.9%) were RSV, 4 (7.4%) were parainfluenza, and 3 (5.6%) were influenza A. No enteroviruses or adenoviruses were detected, and no multiple infections were detected. Only 22 (4.7%) pilgrims received the influenza vaccine. When the results are applied to the total number of pilgrims in 2003, an estimate of 24,000 cases of influenza is obtained.

CONCLUSIONS

The findings from this study suggest a high incidence of influenza as a cause of upper respiratory tract infection among pilgrims, estimated to be 24,000 cases per Hajj season, excluding those becoming ill from contact with Hajj pilgrims returning home. They also indicate a very low vaccination rate for the influenza vaccine; as well as poor knowledge of its existence. Continued surveillance during the Hajj pilgrimage is necessary. The influenza vaccine should be a priority for those attending the Hajj pilgrimage, and should also be considered for antiviral prophylaxis.