Declining Incidence of Invasive Meningococcal Disease in South Africa: 2003-2016

Abstract

Background: Invasive meningococcal disease (IMD) is endemic to South Africa, where vaccine use is negligible. We describe the epidemiology of IMD in South Africa.

Methods: IMD cases were identified through a national, laboratory-based surveillance program, GERMS-SA, from 2003-2016. Clinical data on outcomes and human immunodeficiency virus (HIV) statuses were available from 26 sentinel hospital sites. We conducted space-time analyses to detect clusters of serogroup-specific IMD cases.

Results: Over 14 years, 5249 IMD cases were identified. The incidence was 0.97 cases per 100 000 persons in 2003, peaked at 1.4 cases per 100 000 persons in 2006, and declined to 0.23 cases per 100 000 persons in 2016. Serogroups were confirmed in 3917 (75%) cases: serogroup A was present in 4.7% of cases, B in 23.3%, C in 9.4%; W in 49.5%; Y in 12.3%, X in 0.3%; Z in 0.1% and 0.4% of cases were non-groupable. We identified 8 serogroup-specific, geo-temporal clusters of disease. Isolate susceptibility was 100% to ceftriaxone, 95% to penicillin, and 99.9% to ciprofloxacin. The in-hospital case-fatality rate was 17% (247/1479). Of those tested, 36% (337/947) of IMD cases were HIV-coinfected. The IMD incidence in HIV-infected persons was higher for all age categories, with an age-adjusted relative risk ratio (aRRR) of 2.5 (95% confidence interval [CI] 2.2-2.8; P < .001) from 2012-2016. No patients reported previous meningococcal vaccine exposure. Patients with serogroup W were 3 times more likely to present with severe disease than those with serogroup B (aRRR 2.7, 95% CI 1.1-6.3); HIV coinfection was twice as common with W and Y diseases (aRRR W = 1.8, 95% CI 1.1-2.9; aRRR Y = 1.9, 95% CI 1.0-3.4).

Conclusions: In the absence of significant vaccine use, IMD in South Africa decreased by 76% from 2003-2016. HIV was associated with an increased risk of IMD, especially for serogroup W and Y diseases.

Keywords: Neisseria; South Africa; epidemiology; invasive meningococcal disease; meningococcus.

Figure 1.

Flow chart of laboratory-confirmed cases of IMD reported to GERMS-SA, in South Africa, from 2003–2016 (N = 5249). Abbreviations: HIV, human immunodeficiency virus; IMD, invasive meningococcal disease; PCR, polymerase chain reaction.

Figure 2.

Estimated incidence of invasive meningococcal disease by serogroup and year, in South Africa, from 2003–2016 (N = 5249). Serogroup data were imputed for 1332 cases. The “Other” serogroups included 12 X, 4 Z, and 15 non groupable isolates. Significant increases in disease incidence were seen with serogroup W between 2003 and 2006 (P < .001), followed by significant decreases until 2016 (P < .001). All other serogroups (except Other) showed significant decreases in disease incidence over the 14 years (P < .001). The “Total” group includes all of South Africa.

Figure 3.

Invasive meningococcal disease clusters, by serogroup, by district, occurring in South Africa, from 2005–2015. (A) The serogroup A cluster occurred from January 2005 to September 2008 and had a within-cluster relative risk (RR) of 7.7. (B) There were 2 serogroup B clusters: cluster 1 occurred from June 2005 to November 2010 and had a RR of 2.4; and cluster 2 occurred from July 2007 to August 2011 and had a RR of 8.1. (C) There were 2 serogroup C clusters: cluster 1 occurred from July 2006 to December 2011 and had a RR of 4.5; and cluster 2 occurred from April 2006 to September 2011 and had a RR of 2.5. (D) The serogroup W cluster occurred from April 2005 to September 2010 and had a RR of 6.1. (E) There were 2 serogroup Y clusters: cluster 1 occurred from February 2010 to July 2015 and had a RR of 5.7; and cluster 2 occurred from March 2005 to November 2006 and had a RR of 19.1. The district relative risks were calculated by dividing the observed number of cases per district by the number of cases expected per district (as determined by numbers of patients in the cryptococcosis control group).