Why Is Meningococcal Disease on the Rise in South Africa?
Meningococcal disease is endemic in South Africa. IMD episodes occur throughout the year, with seasonal increases in winter through spring. The causative bacterium Neisseria meningitidis colonises the human nasopharynx and is spread from person to person through respiratory droplets. The disease mostly occurs when the bacteria invade the bloodstream and cause meningitis or bacteraemia (IMD).
Early symptoms include malaise and fever, followed by vomiting, general body aches, cold peripheries, and drowsiness/confusion. The classic purpuric rash is a late symptom of septicaemia and indicates a medical emergency.
Historically, meningococcal disease waxes and wanes over a period of 10–15 years. Two events have impacted meningococcal disease incidence in South Africa over the past 20 years.
From 2005, South Africa experienced a country-wide increase in meningococcal disease due to serogroup W, which caused sustained high rates of disease for over five years. Secondly, during the COVID-19 pandemic, many countries, including South Africa, reported a significant decrease in meningococcal disease and other respiratory droplet-transmitted bacterial pathogens due to the various containment measures implemented to reduce respiratory disease transmissions. Subsequently, since 2022, these bacterial pathogens are returning to pre-COVID pandemic levels.
We report on surveillance findings of laboratory-confirmed IMD in South Africa from the start of the GERMS-SA programme in 2003 through September 2024, with a focus on the trends noted in the post-COVID-19 pandemic years (2021-2024).
Materials and Methods
GERMS-SA is a surveillance programme that has been systematically collecting data on laboratory-confirmed episodes of IMD in South Africa since 2003. All public- and private-sector laboratories are requested to report laboratory-confirmed episodes of N. meningitidis from normally sterile-site specimens (i.e., blood, cerebrospinal fluid, joint fluid, etc.), identified through culture or molecular methods, to the Centre for Respiratory Diseases and Meningitis, National Institute for Communicable Diseases (NICD), for confirmation and further characterisation.
When isolates were available, meningococcal serogroups were determined phenotypically using latex slide agglutination with antisera for capsular polysaccharides A, B, C, W, X, Y, and Z, and this was confirmed using polymerase chain reaction (PCR). Genogrouping was performed on culture-negative specimens.
Results
The last peak in IMD in South Africa occurred in 2006, with an annual incidence of 1.4 episodes per 100,000 persons. In 2021, IMD was at its lowest incidence of 0.05 episodes per 100,000. Currently, disease incidence remains relatively low at 0.18 episodes per 100,000 population, as reported in 2023. Incidence has, however, shown an increasing trend from 2021 but is not yet reaching pre-COVID-19 pandemic levels. Up until week 38 of 2024, 99 laboratory-confirmed invasive meningococcal episodes have been reported (107 total episodes were reported in 2023). Of the 56 episodes from 2024 with known serogroups, serogroup B disease (n=21) remains dominant, followed by serogroups W (n=13), Y (n=13), and C (n=9). Since 2016, serogroup B has replaced serogroup W as the dominant serogroup, with serogroups W and Y fluctuating between second and third place.
Over the years, infants have had the highest IMD incidence (1.6 per 100,000 population in 2023). Incidence decreased with age, with a smaller peak in adolescents and young adults (0.22 per 100,000 persons 15-24 years of age in 2023). All of the four dominant serogroups affect each age category each year. However, since 2019, over half of the disease episodes with known serogroups in infants were serogroup B (46/88).
IMD incidence varies geographically, with coastal provinces generally showing a higher incidence. IMD incidence in the Western Cape Province is higher than any other province (0.61 per 100,000 population in 2023) and was double that of any other province over the past few years. All provinces have shown the same upward trend in disease incidence since 2021, yet remain within the range of the early pre-COVID-19 years.
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