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Single clone responsible for most MenW cases in England, Wales
The increase of invasive meningococcal group W cases throughout England and Wales is the result of a single clone that belongs to the ST-11 complex, according to researchers from Public Health England.
“The emergence and rapid clonal expansion with continuing increase in endemic MenW:cc11 disease in the UK will require close monitoring in the coming years, particularly given that natural immunity against this capsular group is low across all age groups,” the researchers wrote in Clinical Infectious Diseases.
After observing an increase in MenW cases, the researchers identified cases of the disease in England and Wales retrospectively and prospectively and followed them for 3 epidemiological years. Whole genome sequencing was performed on the isolates, and researchers compared the clinical and laboratory data to characterize the disease.
From July 2010 to June 2013, there were 129 laboratory-confirmed cases of MenW invasive meningococcal disease. Among those, 106 were confirmed by culture, and among those, 64 were phenotypically characterized as MenW:2a; 42 were nontypeable. After whole genome sequencing, all 64 of the MenW:2a isolates were confirmed as MenW:cc11, as were seven of the isolates originally characterized as nontypeable. All but one of the MenW:cc11 isolates formed a tight phylogenetic cluster.
Clinical data were available for all of the 129 MenW cases. None of the cases was contacts of other MenW cases, and most cases were previously healthy. Forty-nine percent of patients presented with septicemia, 12% presented with meningitis, and 17% presented with both.
Fifteen patients developed pneumonia, nine developed septic arthritis and five presented with severe upper respiratory tract infection. ICU admission was required for 37% of the patients, and 12% of patients died of meningococcal disease, almost all within 72 hours of diagnosis. There was no association between the disease strain and age at disease, risk factors, clinical presentation, ICU admission or fatality.
“MenW is potentially preventable through vaccination with the quadrivalent MenACWY conjugate vaccine, and if the trend continues to establish itself in children and young adults, then it may be prudent to consider supplementing the current MenC conjugate vaccine program with the quadrivalent conjugate vaccine,” the researchers wrote. “Vaccination of an age group with high MenW carriage, if such a group could be identified, could also potentially prevent overall cases through indirect (herd) protection.”
Disclosure: Two researchers have performed research for Public Health England and St. George’s University of London on behave of Pfizer, GlaxoSmithKline and Novartis Vaccines.