Using evidence to inform response to the 2017 plague outbreak in Madagascar: a view from the WHO African Regional Office.

The 2017 plague outbreak in Madagascar was unprecedented in the African region, resulting in 2417 cases (498 confirmed, 793 probable and 1126 suspected) and 209 deaths by the end of the acute urban pneumonic phase of the outbreak. The Health Emergencies Programme of the WHO Regional Office for Africa together with the WHO Country Office and WHO Headquarters assisted the Ministry of Public Health of Madagascar in the rapid implementation of plague prevention and control measures while collecting and analysing quantitative and qualitative data to inform immediate interventions. We document the key findings of the evidence available to date and actions taken as a result. Based on the four goals of operational research - effective dissemination of results, peer-reviewed publication, changes to policy and practice and improvements in programme performance and health - we evaluate the use of evidence to inform response to the outbreak and describe lessons learned for future outbreak responses in the WHO African region. This article may not be reprinted or reused in any way in order to promote any commercial products or services.

Effect of a serogroup A meningococcal conjugate vaccine (PsA-TT) on serogroup A meningococcal meningitis and carriage in Chad: a community study [corrected].

BACKGROUND: A serogroup A meningococcal polysaccharide-tetanus toxoid conjugate vaccine (PsA-TT, MenAfriVac) was licensed in India in 2009, and pre-qualified by WHO in 2010, on the basis of its safety and immunogenicity. This vaccine is now being deployed across the African meningitis belt. We studied the effect of PsA-TT on meningococcal meningitis and carriage in Chad during a serogroup A meningococcal meningitis epidemic. METHODS: We obtained data for the incidence of meningitis before and after vaccination from national records between January, 2009, and June, 2012. In 2012, surveillance was enhanced in regions where vaccination with PsA-TT had been undertaken in 2011, and in one district where a reactive vaccination campaign in response to an outbreak of meningitis was undertaken. Meningococcal carriage was studied in an age-stratified sample of residents aged 1-29 years of a rural area roughly 13-15 and 2-4 months before and 4-6 months after vaccination. Meningococci obtained from cerebrospinal fluid or oropharyngeal swabs were characterised by conventional microbiological and molecular methods. FINDINGS: Roughly 1·8 million individuals aged 1-29 years received one dose of PsA-TT during a vaccination campaign in three regions of Chad in and around the capital N'Djamena during 10 days in December, 2011. The incidence of meningitis during the 2012 meningitis season in these three regions was 2·48 per 100,000 (57 cases in the 2·3 million population), whereas in regions without mass vaccination, incidence was 43·8 per 100,000 (3809 cases per 8·7 million population), a 94% difference in crude incidence (p<0·0001), and an incidence rate ratio of 0·096 (95% CI 0·046-0·198). Despite enhanced surveillance, no case of serogroup A meningococcal meningitis was reported in the three vaccinated regions. 32 serogroup A carriers were identified in 4278 age-stratified individuals (0·75%) living in a rural area near the capital 2-4 months before vaccination, whereas only one serogroup A meningococcus was isolated in 5001 people living in the same community 4-6 months after vaccination (adjusted odds ratio 0·019, 95% CI 0·002-0·138; p<0·0001). INTERPRETATION: PSA-TT was highly effective at prevention of serogroup A invasive meningococcal disease and carriage in Chad. How long this protection will persist needs to be established. FUNDING: The Bill & Melinda Gates Foundation, the Wellcome Trust, and Médecins Sans Frontères.

Meningitis seasonal pattern in Africa and detection of epidemics: a retrospective study in Niger, 1990-98.

Control of epidemic meningitis is still an unresolved problem in Africa. WHO has promoted the use of surveillance and response following alerts based on weekly threshold levels. In order to avoid any waste of resources related to false-positive alerts, it was decided not to choose too sensitive thresholds. This policy, however, leads to delayed response. The seasonal pattern of epidemics provides a solution to this dilemma. We carried out a retrospective survey of district-level surveillance data in Niger from June 1990 to June 1998. We identified an early and late meningitis season. Following this pattern, we studied the performance of the WHO-recommended threshold as compared to alternative thresholds for identifying early, late and non-epidemic district-years (DYs). (ADY was defined as a 52-week period starting in the last week of June, at the district level). We studied 296 DYs, comprising 50 early epidemic, 38 late epidemic, and 208 non-epidemic DYs. Early epidemics were more often large and accounted for almost 75% of total cases. When applied no later than the first week of March, a highly sensitive alternative threshold resulted in initiation of an alert, with a median of 3 weeks earlier than the standard threshold, with no false-positive alerts, i.e., a specificity of 1.

[First major epidemic caused by Neisseria meningitidis serogroup W135 in Africa?]. / Premiere epidemie de garnde amplier provoquee par Neisseria meningitidis W135 en Afrique?

Neisseria meningitidis serogroup W 135 (N.m. W 135) has caused sporadic infections and small epidemics such as those that occurred during religious pilgrimages in Saudi Arabia in 2000 and in 2001. It is routinely isolated from specimens coming from African countries. The first major epidemic involving N.m. W 135 occurred in Burkina Faso between January and May 1992. There were more than 1300 cases including 1500 deaths. Enhanced surveillance of circulating strains showed that N.m. W 135 accounted for 83% of the 203 positive cerebrospinal fluid specimen cultures. The offending organism was identical to the strain that caused the smaller epidemic in Saudi Arabia in 2000. Due to the shortage of tetravalent meningococcal vaccine against N.m. W 135, the Health Ministry based its response to the epidemic on treatment of symptomatic patients using chloramphenicol and ampicillian. These drugs were distributed free. The emergence of N.m. W135 has impacted public health in Africa. Repeated identification of this serogroup in Burkina Faso during 2002 raises the risk that similar outbreak will occur in the meningitis belt during the next epidemic season. The high cost of tetravalent meningococcal vaccine compounded with the only progressive increase in production capacity underline the need to reinforce surveillance of circulating strains and available treatment facilities. Control strategy for epidemic meningitis is currently the focus of close collaboration between the WHO and the health authorities and corresponding institutions in the countries involved.

[Detection of meningococcal meningitis epidemics in Africa: a new recommendation]. / Mieux détecter les épidémies de méningite à méningocoque en Afrique: une nouvelle recommandation.

In sub-Saharan Africa, the control of meningococcal meningitis epidemics relies on early epidemic detection and mass vaccination. However, experience shows that interventions are often initiated too late to have a significant impact on the epidemic. A new recommendation drafted by participants of a consensus meeting proposes an alert threshold and an epidemic threshold based on the weekly number or incidence of meningitis cases, according to the population size and the epidemic risk, resulting in indicators with high sensitivity and specificity for the detection of an emerging epidemic. Meningitis outbreak investigations must include an assessment of the quality of epidemiologic surveillance. The new recommendation is published in English and French in the Weekly Epidemiologic Record [12]. The success of this consensus meeting shows the value of integrating results from surveillance, field experience and operational research for designing new health strategies.