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Summary Background On April 25, 2017, a cluster of unexplained illnesses and deaths associated with a funeral was reported in Sinoe County, Liberia. Molecular testing identified Neisseria meningitidis serogroup C (NmC) in specimens from patients. We describe the epidemiological investigation of this cluster and metagenomic characterisation of the outbreak strain. Methods We collected epidemiological data from the field investigation and medical records review. Confirmed, probable, and suspected cases were defined on the basis of molecular testing and signs or symptoms of meningococcal disease. Metagenomic sequences from patient specimens were compared with 141 meningococcal isolate genomes to determine strain lineage. Findings 28 meningococcal disease cases were identified, with dates of symptom onset from April 21 to April 30, 2017: 13 confirmed, three probable, and 12 suspected. 13 patients died. Six (21%) patients reported fever and 23 (82%) reported gastrointestinal symptoms. The attack rate for confirmed and probable cases among funeral attendees was 10%. Metagenomic sequences from six patient specimens were similar to a sequence type (ST) 10217 (clonal complex [CC] 10217) isolate genome from Niger, 2015. Multilocus sequencing identified five of seven alleles from one specimen that matched ST-9367, which is represented in the PubMLST database by one carriage isolate from Burkina Faso, in 2011, and belongs to CC10217. Interpretation This outbreak featured high attack and case fatality rates. Clinical presentation was broadly consistent with previous meningococcal disease outbreaks, but predominance of gastrointestinal symptoms was unusual compared with previous African meningitis epidemics. The outbreak strain was genetically similar to NmC CC10217, which caused meningococcal disease outbreaks in Niger and Nigeria. CC10217 had previously been identified only in the African meningitis belt. Funding US Global Health Security.

In France, two sources of data, the mandatory notification and the hospital laboratory network EPIBAC, allow the health authorities to monitor the incidence of bacterial meningitis. In 2002 around 1,500 cases were estimated in France. The more common microorganisms were: Streptococcus pneumoniae 49% (incidence 1.19/100,000), Neisseria meningitidis 33% (incidence 0.83) and Streptococcus agalactiae (Streptococcus B) 11% (incidence 0.27). Listeria monocytogenes accounted for 4% of the cases (incidence 0.11) and Haemophilus influenzae accounted for 3% (incidence 0.08). Trends in incidence showed an increase of meningococci meningitis since 1996, a steady decrease of H. influenzae and Listeria meningitis since 1992, and a quasi stable number of pneumococci meningitis, streptococci B meningitis and tuberculosis meningitis in the last 10 years. The impact of preventive measures on the incidence of Listeria meningitis and H. influenzae b meningitis has been clearly demonstrated through the dramatic decrease of meningitis due to these microorganisms.

In France, two sources of data, the mandatory notification and the laboratory network EPIBAC, allow the health authorities to follow the incidence of bacterial meningitis (BM) and to assess the relative frequency of the micro-organisms responsible for such infection. In 1999, more than 1,000 cases of BM were notified in France. The more common micro-organisms were: Streptococcus pneumoniae 46%, Neisseria meningitidis 32% and Streptococcus agalactiae(or Streptococcus B) 11%. Listeria monocytogenes and Haemophilus influenzae accounted for 6% and 5% of the cases respectively. In 1999, the incidence per 100,000 inhabitants of meningitis due to pneumococci (0.81), to streptococci B (0.19) and tuberculosis meningitis (0.17) were stable since 1995. The incidence rate of meningitis due to Listeria (0.10) and to H. influenzae (0.08) shows a regular decrease since 1992. The impact of preventive measures of meningitis due to Listeria and H. influenzae B has been clearly demonstrated through the dramatic decrease of meningitis due to these micro-organisms.

On April 3 and 7, 2000, four cases of Neisseria meningitidis serogroup W135 infection were diagnosed in France in Raj pilgrims and their close relatives. Two cases were fatal. Due to the rarity of this strain in France, a strain belonging to a clonal complex implicated in several epidemics in Europe and North America, and it high mortality observed, The French General Direction of Heal issued recommendations on April 8th for rifampicin chemotherapy for all pilgrims and relatives living in their home. The national disease watch (Institut de Veille Sanitaire, InVS) conducted an investigation to describe the epidemic and follow the diffusion of the strain in the population and assess the impact of preventive measures taken as well as need for other specific measures.A case was considered to be confirmed when the strain isolated from usually sterile media after March 22 was found to be identical to the epidemic strain (W135, 2a: P1-2.5--clonal complex ET37). A case was considered probable when a pilgrim or in a person in contact with a pilgrim had clinical meningitis (purulent cerebrospinal fluid or purpura fulminans) or when the identified strain was in the W135 serogroup but could not be further identified. A standardized questionnaire developed in collaboration with the European countries concerned by the epidemic was filled out.By November 20, 2000, 25 confirmed and 2 probable cases were identified; 85% of the cases occurred during the first 7 weeks of the epidemic. Mortality was 18%. Patients aged over 50 years accounted for 66% of the cases (6/9) occurring before April 9, 2000 and 17% of the cases (3/18) observed after this data. Four patients had single-joint arthritis. No cluster cases could be identified. Four cases occurred among 19,100 pilgrims (attack rate 21/100,000), 9 among persons living with pilgrims, 7 among subjects in direct contact with pilgrims but not living with them, and 7 among persons who had no identifiable contact with pilgrims. These last 7 cases occurred after the 3rd week of the epidemic. No cases occurred among persons who had taken rifampicin chemoprophylaxis. Eighteen cases occurred after diffusion of the prophylaxis recommendations including 5 in a population directly concerned by the recommendations.These data suggest that the epidemic strain is not different from other strains in terms of virulence and transmissibility. Eight months after the Raj, the number of cases related to the epidemic remained limited in France. The characteristics of the most recent cases do however suggest an epidemic clone persists in the general population. The Direction of Health recommends vaccination using the quadrivalent A,C,W135,Y vaccine for the 2001 Raj.