Increase in endemic Neisseria meningitidis capsular group W sequence type 11 complex associated with severe invasive disease in England and Wales.
BACKGROUND
In England and Wales, the incidence of invasive meningococcal disease has been declining for more than a decade, but meningococcal group W (MenW) cases have been increasing since 2009.


METHODS
Public Health England conducts enhanced national surveillance of invasive meningococcal disease in England and Wales. Detailed clinical information was obtained for all laboratory-confirmed MenW cases diagnosed during 3 epidemiologic years (2010-2011 to 2012-2013), alongside whole-genome sequencing analysis of the clinical isolates.


RESULTS
The year-on-year increase in invasive MenW disease across all age groups since 2009-2010 was due to rapid endemic expansion of a single clone belonging to the sequence type 11 complex (cc11). In 2013-2014, MenW was responsible for 15% of all invasive meningococcal disease. All but 1 of the recent MenW:cc11 isolates were very closely related, consistent with recent clonal expansion. Clinical follow-up of all 129 MenW cases diagnosed during 2010-2011 to 2012-2013 revealed that most patients were previously healthy (n = 105 [81%]), had not travelled abroad prior to illness and the majority presented with septicemia (n = 63 [49%]), meningitis (n = 16 [12%]) or both (n = 21 [16%]); however, one-quarter had atypical presentations including pneumonia (n = 15 [12%]), septic arthritis (n = 9 [7%]), and epiglottitis/supraglottitis (n = 5 [4%]). Forty-eight (37%) required intensive care and 15 (12%) died. There was no association between infecting strain, clinical disease, or outcome.


CONCLUSIONS
The recent increase in invasive MenW disease in England and Wales is due to rapid endemic expansion of a single clone belonging to cc11 and is associated with severe disease with unusual clinical presentations. This increase will require careful monitoring in the coming years.
Immunisation Department, Public Health England Paediatric Infectious Diseases Research Group, St George's University of London.
Shamez N
SN
Ladhani
Immunisation Department, Public Health England.
Kazim
K
Beebeejaun
Meningococcal Reference Unit, Public Health England, Manchester Medical Microbiology, Manchester Royal Infirmary, United Kingdom.
Jay
J
Lucidarme
Immunisation Department, Public Health England.
Helen
H
Campbell
Meningococcal Reference Unit, Public Health England, Manchester Medical Microbiology, Manchester Royal Infirmary, United Kingdom.
Steve
S
Gray
Meningococcal Reference Unit, Public Health England, Manchester Medical Microbiology, Manchester Royal Infirmary, United Kingdom.
Ed
E
Kaczmarski
Immunisation Department, Public Health England.
Mary E
ME
Ramsay
Meningococcal Reference Unit, Public Health England, Manchester Medical Microbiology, Manchester Royal Infirmary, United Kingdom.
Ray
R
Borrow
D000293:Adolescent; D000328:Adult; D000368:Aged; D001170:Arthritis, Infectious / Q000453:epidemiology / Q000382:microbiology; D016667:Bacterial Capsules / Q000145:classification; D002648:Child; D002675:Child, Preschool; D019353:Endemic Diseases; D004739:England / Q000453:epidemiology; D062665:Epidemiological Monitoring; D005260:Female; D005500:Follow-Up Studies; D016680:Genome, Bacterial; D006801:Humans; D007223:Infant; D008297:Male; D008585:Meningitis, Meningococcal / Q000453:epidemiology* / Q000382:microbiology*; D008589:Meningococcal Infections / Q000145:classification / Q000453:epidemiology* / Q000382:microbiology* / Q000401:mortality; D008875:Middle Aged; D009345:Neisseria meningitidis / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D010641:Phenotype; D010802:Phylogeny; D018410:Pneumonia, Bacterial / Q000453:epidemiology / Q000382:microbiology; D011446:Prospective Studies; D012189:Retrospective Studies; D018805:Sepsis / Q000453:epidemiology / Q000382:microbiology; D017422:Sequence Analysis, DNA; D059525:Supraglottitis / Q000453:epidemiology / Q000382:microbiology; D014852:Wales / Q000453:epidemiology; D055815:Young Adult
ST-11 clonal complex; epidemiology; meningococcal W disease; meningococcal pneumonia; travel