Australian Meningococcal Surveillance Programme Annual Report, 2025

Abstract

In Australia, both probable and laboratory-confirmed cases of invasive meningococcal disease (IMD) are reported to the National Notifiable Diseases Surveillance System (NNDSS). When compared to 2024, the number of IMD notifications in 2025 decreased by 13% to 118. IMD was confirmed by laboratory testing in 115/118 (97%) of 2025 IMD cases, with 66% (76/115) diagnosed by bacterial culture and 34% (39/115) by nucleic acid amplification testing. The genogroup was determined for 93% of laboratory-confirmed cases (107/115): genogroup B (MenB) accounted for 82.2% of infections (88/107); MenW and MenY for 7.5% of disease (8/107) each; MenC for 1.9% (2/107); and MenA for 0.9% (1/107). Finetyping was available for 67% of the cases for which the genogroup was determined (72/107). In MenB isolates, 28 porA types were detected: the most prevalent from amongst these were P1.7-2,4 (21%; 12/58) and P1.7,16-26 (14%; 8/58). Of the eight MenW isolates in 2025, six were finetyped and identified as porA type P1.5,2, MLST (ST) 11 and belonging to the clonal complex 11, the hypervirulent strain reported in outbreaks in Australia and overseas. In MenY infections, four porA types were detected from the five isolates finetyped: P1.21,16; P1.5,10-1; P1.5-1,10-1; and P1.5-2,10-1, with no dominant porA type detected. One of the two MenC isolates was typed, identifying as P1.5-2,10-1 and the single MenA isolate identified as P1.5-2,10.

Peaks of IMD occurred in children aged less than 5 years, in those aged 15–24 years, and in adults aged 25–44 years, accounting for 18% (21/115), 23% (26/115) and 22% (25/115) of laboratory-confirmed cases, respectively. In children aged under 5 years, 100% of IMD (21/21) was MenB; in those aged 15–24 years, 100% of IMD (25/25) was MenB; and in those aged 25–44 years, 82% of IMD (18/22) was MenB, with three MenW cases and one MenC case reported in this age group. IMD was reported in all age groups: < 5 years (18%; 21/115); 5–9 years (5%; 6/115); 10–14 years (2.6%; 3/115); 15–24 years (23%; 26/115); 25–44 years (22%; 25/115); 45–64 years (12%; 14/115); and in those aged 65 years and older (17%; 20/115). Whilst MenB predominated in all age groups, the majority of MenY IMD cases (6/8) were reported in adults aged 65 years and older, among whom it accounted for 6/18 cases (33%).

All cultured IMD isolates available for antimicrobial susceptibility testing (n = 76) were tested for ceftriaxone and penicillin. Minimum inhibitory concentration (MIC) values were reported using Clinical Laboratory Standards Institute (CLSI) interpretative criteria: 8% (6/76) were defined as penicillin resistant (MIC value ≥ 0.5mg/L); 64% (49/76) had intermediate susceptibility to penicillin (MIC values 0.125 and 0.25 mg/L); and 28% (21/76) were susceptible to penicillin (MIC values ≤ 0.064 mg/L). All isolates tested were susceptible to ceftriaxone, ciprofloxacin and rifampicin.