First serogroup Y meningitis outbreak in Hubei Province Central China linked to adolescent immunization gaps

Meningococcal meningitis poses a persistent public health threat globally, with evolving epidemic serogroups complicating prevention especially in China in recent years. On May 27, 2024, Hubei Province (central China) reported its first laboratory-confirmed case of serogroup Y Meningococcal meningitis in a student aged 14 from L County, E City. This study aimed to characterize the outbreak, identify transmission drivers, and provide evidence for targeted control strategies. A field investigation was conducted involving case definition (suspected/probable/confirmed cases, carriers), epidemiological interviews (symptom onset, vaccination history, exposures), and laboratory testing. We analyzed 199 close contacts and expanded sampling population via nucleic acid testing and bacterial culture. Isolated serogroup Y strains were subjected to whole-genome sequencing, phylogenetic analysis, and antibiotic susceptibility testing. One confirmed serogroup Y meningococcal meningitis case and 13 Neisseria meningitidis (Nm) carriers (Five serogroup Y) were identified. The index case (an eighth grade student) had completed the national serogroup A / serogroups A and C meningococcal vaccination schedule (last dose: 2016), but serogroup Y vaccination was absent in the index case and all classmates. Nucleic acid testing positivity of Nm was 6.5% (13/199) among contacts and expanded sampling population, with 2.5% (5/199) serogroup Y carriers. All five serogroup Y isolates (LF-strains) belonged to ST-1655 (ST-23 clonal complex) and were phylogenetically close to strains from other Chinese provinces. Antibiotic susceptibility testing confirmed susceptibility to six antibiotics (Penicillin, Ampicillin, Ciprofloxacin, Ceftriaxone, Azithromycin and Rifampicin). Emergency ACYW135 vaccination achieved 57.5% coverage in the affected school, with no secondary cases. This is the first report of serogroup Y Meningococcal meningitis in Hubei Province, caused by the hyper-invasive ST-1655 (ST-23 clonal complex). Adolescent immunity gaps to serogroup Y were the primary driver. To combat meningococcal meningitis in China, we recommend integrating serogroup Y into routine vaccination especially for adolescents, strengthening serogroup-specific surveillance, and enhancing local laboratory capacity for rapid meningococcal meningitis diagnosis.