• Diphtheria outbreak with high mortality in northeastern Nigeria

      Besa, N C; Coldiron, M E; Bakri, A; Raji, A; Nsuami, M J; Rousseau, C; Hurtado, N; Porten, K; Epicentre, Paris, France. (Cambridge University Press, 2013-07-18)
      SUMMARY A diphtheria outbreak occurred from February to November 2011 in the village of Kimba and its surrounding settlements, in Borno State, northeastern Nigeria. We conducted a retrospective outbreak investigation in Kimba village and the surrounding settlements to better describe the extent and clinical characteristics of this outbreak. Ninety-eight cases met the criteria of the case definition of diphtheria, 63 (64·3%) of whom were children aged <10 years; 98% of cases had never been immunized against diphtheria. None of the 98 cases received diphtheria antitoxin, penicillin, or erythromycin during their illness. The overall case-fatality ratio was 21·4%, and was highest in children aged 0-4 years (42·9%). Low rates of immunization, delayed clinical recognition of diphtheria and absence of treatment with antitoxin and appropriate antibiotics contributed to this epidemic and its severity.
    • Epidemiological and clinical aspects of human Brucella suis infection in Polynesia

      Guerrier, G; Daronat, J M; Morisse, L; Yvon, J F; Pappas, G; Epicentre, Paris, France; Agence de Santé, Mata Utu, Wallis, France; Institute of Continuing Medical Education of Ioannina, Greece; International Society of Chemotherapy Zoonoses Working Group, London, UK (Cambridge University Press, 2011-06-21)
      High brucellosis seroprevalence rates in domestic swine herds have been reported in Wallis and Futuna Islands and are associated with a significant burden of human infection by Brucella suis, a species that is rarely incriminated in human disease. Between 2003 and 2010, seven patients had a positive blood culture for B. suis biovar 1, 11 symptomatic patients had a positive Rose Bengal test (RBT) and a positive serum agglutination test (SAT) and three asymptomatic cases were found to be positive for RBT, SAT or ELISA IgM (after systematic screening of 52 family members of 15 index cases). Overall, Brucella infection was diagnosed in 21 people, corresponding to a mean annual incidence of 19 cases/100 000 inhabitants. Compared to series of patients infected with other more commonly encountered Brucella spp. such as B. melitensis and B. abortus, clinical presentation and percentage and distribution of complications were similar, apart from a marked observation of significantly increased median alanine aminotransferase levels, 20 times greater than upper normal rates, but not accompanied by any particular hepatic pathology. Wallis and Futuna, where people live in close proximity to animals and where the cultural significance of pig-raising precludes the implementation of adequate veterinary preventive measures, thus represents one of the few known B. suis foci worldwide and allows for evaluation of the peculiarities of this infection.
    • The incubation period of hepatitis E genotype 1: insights from pooled analyses of travellers

      Azman, AS; Ciglenecki, I; Oeser, C; Said, B; Tedder, RS; Ijaz, S (Cambridge University Press, 2018-05-24)
      Hepatitis E virus genotype 1 (HEV G1) is an important cause of morbidity and mortality in Africa and Asia. HEV G1's natural history, including the incubation period, remains poorly understood, hindering surveillance efforts and effective control. Using individual-level data from 85 travel-related HEV G1 cases in England and Wales, we estimate the incubation period distribution using survival analysis methods, which allow for appropriate inference when only time ranges, rather than exact times are known for the exposure to HEV and symptom onset. We estimated a 29.8-day (95% confidence interval (CI) 24.1-36.0) median incubation period with 5% of people expected to develop symptoms within 14.3 days (95% CI 10.1-21.7) and 95% within 61.9 days (95% CI 47.4-74.4) of exposure. These estimates can help refine clinical case definitions and inform the design of disease burden and intervention studies.
    • Modelling the first dose of measles vaccination: the role of maternal immunity, demographic factors, and delivery systems.

      Metcalf, C J E; Klepac, P; Ferrari, M; Grais, R F; Djibo, A; Grenfell, B T; Department of Ecology and Evolutionary Biology, Princeton University, NJ 0854, USA. cmetcalf@princeton.edu (Cambridge University Press, 2011-02)
      Measles vaccine efficacy is higher at 12 months than 9 months because of maternal immunity, but delaying vaccination exposes the children most vulnerable to measles mortality to infection. We explored how this trade-off changes as a function of regionally varying epidemiological drivers, e.g. demography, transmission seasonality, and vaccination coverage. High birth rates and low coverage both favour early vaccination, and initiating vaccination at 9-11 months, then switching to 12-14 months can reduce case numbers. Overall however, increasing the age-window of vaccination decreases case numbers relative to vaccinating within a narrow age-window (e.g. 9-11 months). The width of the age-window that minimizes mortality varies as a function of birth rate, vaccination coverage and patterns of access to care. Our results suggest that locally age-targeted strategies, at both national and sub-national scales, tuned to local variation in birth rate, seasonality, and access to care may substantially decrease case numbers and fatalities for routine vaccination.
    • Spatial dynamics of meningococcal meningitis in Niger: observed patterns in comparison with measles

      Bharti, N; Broutin, H; Grais, R F; Ferrari, M J; Djibo, A; Tatem, A J; Grenfell, B T; Department of Ecology and Evolutionary Biology and Center for Health and Wellbeing, Woodrow Wilson School of Public and International Affairs, Princeton University, Princeton NJ, USA; MIVEGEC, UMR CNRS 5290, IRD 224, UM1, UM2, Montpellier, France; Epicentre, Paris, France; Department of Biology, Department of Statistics, and Center for Infectious Disease Dynamics, Penn State University, PA, USA; Ministry of Health, Niamey, Niger; Emerging Pathogens Institute and Department of Geography, University of Florida, Gainesville FL, USA; Fogarty International Center, National Institutes of Health, Bethesda MD, USA (Cambridge University Press, 2011-10-05)
      SUMMARYThroughout the African meningitis belt, meningococcal meningitis outbreaks occur only during the dry season. Measles in Niger exhibits similar seasonality, where increased population density during the dry season probably escalates measles transmission. Because meningococcal meningitis and measles are both directly transmitted, we propose that host aggregation also impacts the transmission of meningococcal meningitis. Although climate affects broad meningococcal meningitis seasonality, we focus on the less examined role of human density at a finer spatial scale. By analysing spatial patterns of suspected cases of meningococcal meningitis, we show fewer absences of suspected cases in districts along primary roads, similar to measles fadeouts in the same Nigerien metapopulation. We further show that, following periods during no suspected cases, districts with high reappearance rates of meningococcal meningitis also have high measles reintroduction rates. Despite many biological and epidemiological differences, similar seasonal and spatial patterns emerge from the dynamics of both diseases. This analysis enhances our understanding of spatial patterns and disease transmission and suggests hotspots for infection and potential target areas for meningococcal meningitis surveillance and intervention.