3.

Epidemiology

The incidence of bacterial meningitis is estimated to be over 1.2 million cases worldwide yearly. (27) Bacterial meningitis has the highest global burden with Neisseria meningitidis (N. meningitidis, meningococcal meningitis) having the highest potential for large epidemics. (28) In 2001, meningococcal meningitis accounted for 48% of meningitis cases and is the most common cause of meningitis in England and Wales. (29)

The fatality rate without treatment is estimated to be as high as 70%, 1/10 of bacterial meningitis sufferers die and 1/5 survivors of bacterial meningitis are left with severe disabilities (27) such as cognitive impairment, hearing loss, motor weakness, and other disorders. Worldwide there is an incidence of 500,000-1,200,000 invasive meningococcal diseases each year and 50-000-135,000 deaths. (30)

Fatality and incidence rates for meningitis vary worldwide depending on region, pathogen type, and age groups (27) and are closely related to the sociodemographic index. (31) Young people and babies are at the highest risk from meningococcal. (32) Severity of meningitis is generally milder from viral than from bacterial infections. The morbidity and mortality of children in England is currently highest from serogroup B of meningococcal infection [FIGURE 1] (29) and it has caused outbreaks of meningitis at US universities. (33) This serogroup has the highest burden of disease on Europe since 1970 and is dominant in all age groups below 65. [FIGURE 2] (34)

Figure 1: Worldwide distribution of major meningococcal serogroups and of serogroup B outbreaks by serotype (shaded in purple). The meningitis belt (dotted line) of sub-Saharan Africa and other areas of substantial meningococcal disease in Africa are shown. (35)

Figure 2: Distribution of confirmed cases of invasive meningococcal disease per 100 000 population, (36)

The incidence and mortality rate of meningitis caused by N. meningitidis is highest in the meningitis belt located in sub-Saharan Africa. [FIGURE 3] The hyper-endemic region characterized by seasonal meningitis epidemics extends from Senegal to Ethiopia. At least 350 million people in this region are at risk of meningitis during annual epidemics. (27) Pre-vaccine programs this region accounted for around 80-85% of meningitis epidemics. (32) Since 1905 major epidemics of meningococcal meningitis have occurred every few years in an epidemic cycle and resulted in a massive 1996 epidemic with nearly 200,000 cases. True burden of meningitis on this region cannot be accurately calculated as reporting systems break down during epidemics and many people die before reaching health centres. A very recent large-scale epidemic occurred in 2009 with a total of 88,199 incidence and a 6.1% fatality rate in the meningitis belt. Over 85% of these cases occurred in North Nigeria and Niger due to presence of N. Meningitidis. [TABLE 1] (37)

Table 1: Average Annual Incidence (Cases per 100 000 Persons) of Suspected, Probable, and Laboratory-Confirmed Meningitis, MenAfriNet, 2015–2017 (38)

Figure 3: Age-standardised incidence of meningitis per 100 000 population by location for both sexes, 2016 (31)

Risk factors that predispose communities to meningitis epidemics include overcrowding, malnutrition, HIV incidence, immunization absence, and sickle cell disease with are all predominant in this region. (31) High risk of meningitis caused by overcrowding is greatly exhibited in refugee camps, overcrowded student households, and military settings. (32) From 1929 to 2018 the WHO reported an incidence of 2,628,283 cases and mortality rate of 151,808 in Africa during the meningitis period. The special distribution of meningitis cases spread rapidly over Africa between 1928 and 2002 but has become more localized to the African meningitis belt between 2003 and 2018. [FIGURE 4] (39)

Figure 4: Spatial distribution of meningitis cases by country in Africa from 1928 to 2018 (Note that meningitis cases information is unavailable for the period 1948–1957). The areas in grey illustrate the different countries belonging to the meningitis belt. (39)

References

27. Harrison, L., Trotter, C. & Ramasay, M., 2009. Global epidemiology of meningococcal disease. Vaccine, Volume 27, p. B51–B63.

28. WHO, n.d. World Health Organisation: Meningitis Overview. [Online]Available at: https://www.who.int/health-topics/meningitis#tab=tab_1[Accessed 7 November 2021].

29. Davison, K. & Ramsay, M., 2003. The epidemiology of acute meningitis in children in England and Wales. Archives of Disease in Childhood, 88(8), p. 662–664.

30. Gabutti, G. & Stefanati, A. a. K. P., 2015. Epidemiology of Neisseria meningitidis infections: case distribution by age and relevance of carriage. Journal of preventive medicine and hygiene, 56(3), pp. E116-20.

31. Zunt, J. e. a., 2018. Global, regional, and national burden of meningitis, 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016. The Lancet Neurology, 17(12), p. 1061–1082.

32. WHO, 2021. World Health Organisation: Meningitis. [Online]
Available at: https://www.who.int/news-room/fact-sheets/detail/meningitis
[Accessed 7 November 2021].

33. Linder, K. a. M. P., 2019. Meningococcal Meningitis. JAMA, 321(10), p. 1014.

34. ECDC, 2021. European Centre for Disease Prevention and Control: Factsheet about meningococcal disease. [Online]
Available at: https://www.ecdc.europa.eu/en/meningococcal-disease/factsheet
[Accessed 7 November 2021].

35. Stephens, D. S., Greenwood, B. & Brandtzaeg, P., 2007. Epidemic meningitis, meningococcaemia, and Neisseria meningitidis. The Lancet, 369(9580), pp. 2196-2210.

36. ECDC, 2017. European Centre for Disease Prevention and Control. Invasive Meningococcal Disease: Annual Epidemiological Report for 2015.

37. Mohammed, I. & Iliyasu, G. a. H. A., 2017. Emergence and control of epidemic meningococcal meningitis in sub-Saharan Africa.. Pathogens and Global Health, 111(1), p. 1–6.

38. Soeters, H. M. et al., 2019. Bacterial Meningitis Epidemiology in Five Countries in the Meningitis Belt of Sub-Saharan Africa, 2015–2017. The Journal of Infectious Diseases, 220(4), pp. S165-S174.

39. Mazamay, S. e. a., 2021. An overview of bacterial meningitis epidemics in Africa from 1928 to 2018 with a focus on epidemics “outside-the-belt.”. BMC Infectious Diseases, Volume 21, p. 1027.