Emergence of endemic serogroup W135 meningococcal disease associated with a high mortality rate in South Africa.
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<.001). The incidence of W135 disease increased in all age groups. Rates were highest among infants (age, <1 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.
von Gottberg
Anne
A
Respiratory and Meningeal Pathogens Research, National Institute for Communicable Diseases, Private Bag X4, Sandringham, 2131, Gauteng, South Africa. annev@nicd.ac.za
du Plessis
Mignon
M
Cohen
Cheryl
C
Prentice
Elizabeth
E
Schrag
Stephanie
S
de Gouveia
Linda
L
Coulson
Garry
G
de Jong
Gillian
G
Klugman
Keith
K
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D021821:Communicable Diseases, Emerging / Q000453:epidemiology / Q000382:microbiology*; D016521:Electrophoresis, Gel, Pulsed-Field / Q000379:methods; D019353:Endemic Diseases; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008585:Meningitis, Meningococcal / Q000453:epidemiology* / Q000382:microbiology / Q000401:mortality; D008875:Middle Aged; D038582:Neisseria meningitidis, Serogroup W-135 / Q000235:genetics / Q000302:isolation & purification*; D018571:Sentinel Surveillance; D013019:South Africa / Q000453:epidemiology