Meningococcal disease burden and transmission in crowded settings and mass gatherings other than Hajj/Umrah: A systematic review.

Background: Mass gatherings (MGs) such as the Hajj and Umrah pilgrimages are known to amplify the risk of invasive meningococcal disease (IMD) due to enhanced transmission of the organism between attendees. The burden of IMD at MGs other than Hajj and Umrah has not previously been quantified through a systematic review.

Methods: A systematic search for relevant articles in PubMed and Embase was conducted using MeSH terms; this was buttressed by hand searching. Following data abstraction, a narrative synthesis was conducted to quantify the burden of IMD at MGs and identify potential risk factors and mitigation measures.

Results: Thirteen studies reporting occurrence of IMD at MGs or similar crowded settings were identified. Eight studies reported cases or outbreaks in MGs of ≥1000 people; five others reported IMD in other crowded settings; all occurred between 1991 and 2015. All age groups were involved in the identified studies; however the majority of cases (∼80%) were young people aged 15-24 years. The number of affected people ranged from one to 321 cases and the overall crude estimate of incidence was calculated as 66 per 100,000 individuals. Serogroups A, C, B and W were identified, with serogroups A and C being most common. Of 450 cases of IMD reported in non-Hajj/Umrah MGs, 67 (14.9%) had fatal outcomes.

Conclusion: IMD outbreaks at non-Hajj/Umrah MGs are generally much smaller than Hajj-related outbreaks and affect mainly young people. Health education and vaccination should be considered for attendees of high risk non-Hajj/Umrah MGs, especially those involving adolescents and young adults.