Eurosurveillance - Volume 30, Issue 31, 07 August 2025

England is experiencing an increase in serogroup W invasive meningococcal disease (IMD) caused by ‘strain A’ of the meningococcal sequence type 11 clonal complex (MenW:cc11) Hajj strain sublineage. Travel-associated and non-travel-associated meningococci from four strain A substrains (A1–A4) accounted for 32 of 59 MenW IMD cases between January 2024 and June 2025, 14 in people returning from Saudi Arabia or household contacts; eight of 14 linked to Umrah pilgrimage. Communications about MenACWY vaccination for pilgrims year-round should be reinforced.

Genomic analysis was performed on Neisseria meningitidis isolates from four cases of invasive meningococcal disease (IMD) identified in Italy after travel to Saudi Arabia in 2025. The cases were not epidemiologically related. The isolates from the cases were whole genome sequenced and belonged to serogroup W, sequence type (ST)-11, clonal complex (CC)11 and were susceptible to ceftriaxone, ciprofloxacin, penicillin G and rifampicin. Phylogenetic analysis grouped the four genomes with the Hajj strain sublineage.

In April 2025, a human seasonal reassortant influenza A(H1N2) virus with a 7:1 genetic constellation was detected in Sweden in a patient seeking primary care for influenza-like illness. The neuraminidase gene of this virus was from A(H3N2) and the remaining genes from A(H1N1)pdm09. The patient recovered. No additional cases have been detected through routine surveillance. This is so far the only identified A(H1N2) reassortant among three seasonal A(H1N1)pdm09 and A(H3N2) reassortants reported in GISAID from Europe during the 2024/25 season.