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Paper of the Month May 2018

Acquisition of Virulence Genes by a Carrier Strain Gave Rise to the Ongoing Epidemics of Meningococcal Disease in West Africa

Proceedings of the National Acadamy of Sciences, U.S.A. https://doi.org/10.1073/pnas.1802298115


Ola Brønstad Brynildsrud, Vegard Eldholm, Jon Bohlin, Kennedy Uadiale, Stephen Obaro, and Dominique A. Cauganta


Division for Infection Control and Environmental Health, Norwegian Institute of Public Health, 0456 Oslo, Norway Nigeria Emergency Response Unit, Médecins sans Frontières, Sokoto, Nigeria Division of Pediatric Infectious Diseases, University of Nebraska Medical Center, Omaha, NE, USA International Foundation Against Infectious Disease in Nigeria, Abuja, Nigeria WHO Collaborating Centre for Reference and Research on Meningococci, Norwegian Institute of Public Health, 0456 Oslo, Norway Department of Community Medicine, Faculty of Medicine, University of Oslo, 0372 Oslo, Norway


In the African meningitis belt, a region of sub-Saharan Africa comprising 22 countries from Senegal in the west to Ethiopia in the east, large epidemics of serogroup A meningococcal meningitis have occurred periodically. After gradual introduction from 2010 of mass vaccination with a monovalent meningococcal A conjugate vaccine, serogroup A epidemics have been eliminated. Starting in 2013, the northwestern part of Nigeria has been affected by yearly outbreaks of meningitis caused by a novel strain of serogroup C Neisseria meningitidis (NmC). In 2015, the strain spread to the neighboring country Niger, where it caused a severe epidemic. Following a relative calm in 2016, the largest ever recorded epidemic of NmC broke out in Nigeria in 2017. Here, we describe the recent evolution of this new outbreak strain and show how the acquisition of capsule genes and virulence factors by a strain previously circulating asymptomatically in the African population led to the emergence of a virulent pathogen. This study illustrates the power of long-read whole-genome sequencing, combined with Illumina sequencing, for high-resolution epidemiological investigations.