Carriage of Neisseria meningitidis in the Hajj and Umrah mass gatherings.

Meningococcal disease is a serious public health threat, especially during mass gatherings such as Hajj and Umrah which provide optimal conditions for disease transmission. The disease is caused by Neisseria meningitidis and transmitted mainly via asymptomatic carriers. A review of the literature on asymptomatic N. meningitidis carriage among Hajj and Umrah pilgrims and their household contacts was performed. Carriage studies reported carriage rates to be higher in Hajj pilgrims compared to Umrah pilgrims and that these events promote acquisition of carriage among pilgrims. With some outliers, most studies found carriage rates among pilgrims to be comparable to those in populations under non-epidemic settings. However, these results should be interpreted with caution, taking into account the limitations within the studies identified. A wide variety of N. meningitidis serogroups appear to be circulating among Hajj and Umrah pilgrims, with serogroups W135 and B being most prominent. Current Hajj and Umrah meningococcal disease preventative measures do not necessarily prevent carriage and transmission, which may result in local and international outbreaks among susceptible populations. Monitoring carriage states of visitors and local inhabitants in the Kingdom of Saudi Arabia, as well as the implementation of preventive measures that impact carriage, are warranted to reduce the risk of Hajj and Umrah-related meningococcal disease outbreaks.