Hyperinvasive Neisseria meningitidis in China Originates from Commensals in Healthy Carriers

In June 2024, a novel hyperinvasive strain of Neisseria meningitidis ( N. meningitidis ) caused the deaths of two middle school students in Qinghai Province, China. This is the first hyperinvasive strain to emerge in the country since 2003 and likely originated from commensal strains in healthy carriers. Whole-genome sequencing identified the strain as serogroup C ST-8491, a commensal lineage circulating in China for over 15 years. Among close contacts, all of whom were classmates, the carriage rate reached 31.4%. Carrier ST-8491 isolates shared 98.5–99.9% genomic identity with the fatal strain. Two genetic variations—a duplication in the opal gene and a capsule polysaccharide synthesis locus variation acquired from the commensal, nonserogroupable ST-18331 strain—were identified as potential virulence factors. These findings demonstrate that commensal strains can directly evolve into fatal forms and underscore the need to monitor N. meningitidis transmission in healthy populations to prevent future outbreaks.