Article,

Emergence of endemic serogroup W135 meningococcal disease associated with a high mortality rate in South Africa

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Clinical Infectious Diseases: An Official Publication of the Infectious Diseases Society of America, 46 (3): 377--86 (February 2008)PMID: 18181736.
DOI: 10.1086/525260

Abstract

BACKGROUND: In the African meningitis belt, Neisseria meningitidis serogroup W135 has emerged as a cause of epidemic disease. The establishment of W135 as the predominant cause of endemic disease has not been described. METHODS: We conducted national laboratory-based surveillance for invasive meningococcal disease during 2000-2005. The system was enhanced in 2003 to include clinical data collection of cases from sentinel sites. Isolates were characterized by pulsed-field gel electrophoresis and multilocus sequence typing. RESULTS: A total of 2135 cases of invasive meningococcal disease were reported, of which 1113 (52\%) occurred in Gauteng Province, South Africa. In this province, rates of disease increased from 0.8 cases per 100,000 persons in 2000 to 4.0 cases per 100,000 persons in 2005; the percentage due to serogroup W135 increased from 7\% (4 of 54 cases) to 75\% (221 of 295 cases). The median age of patients infected with serogroup W135 was 5 years (interquartile range, 2-23 years), compared with 21 years (range, 8-26 years) for those infected with serogroup A (P\textless.001). The incidence of W135 disease increased in all age groups. Rates were highest among infants (age, \textless1 year), increasing from 5.1 cases per 100,000 persons in 2003 to 21.5 cases per 100,000 persons in 2005. Overall case-fatality rates doubled, from 11\% in 2003 to 22\% in 2005. Serogroup W135 was more likely to cause meningococcemia than was serogroup A (82 28\% of 297 cases vs. 11 8\% of 141 cases; odds ratio, 8.9, 95\% confidence interval, 2.2-36.3). A total of 285 (95\%) of 301 serogroup W135 isolates were identified as 1 clone by pulsed-field gel electrophoresis; 7 representative strains belonged to the ST-11/ET-37 complex. CONCLUSIONS: Serogroup W135 has become endemic in Gauteng, South Africa, causing disease of greater severity than did the previous predominant serogroup A strain.

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