SummaryBackgroundIn war-torn Yemen, reports of confirmed cholera started in late September, 2016. The disease continues to plague Yemen today in what has become the largest documented cholera epidemic of modern times. We aimed to describe the key epidemiological features of this epidemic, including the drivers of cholera transmission during the outbreak.MethodsThe Yemen Health Authorities set up a national cholera surveillance system to collect information on suspected cholera cases presenting at health facilities. Individual variables included symptom onset date, age, severity of dehydration, and rapid diagnostic test result. Suspected cholera cases were confirmed by culture, and a subset of samples had additional phenotypic and genotypic analysis. We first conducted descriptive analyses at national and governorate levels. We divided the epidemic into three time periods: the first wave (Sept 28, 2016, to April 23, 2017), the increasing phase of the second wave (April 24, 2017, to July 2, 2017), and the decreasing phase of the second wave (July 3, 2017, to March 12, 2018). We reconstructed the changes in cholera transmission over time by estimating the instantaneous reproduction number, Rt. Finally, we estimated the association between rainfall and the daily cholera incidence during the increasing phase of the second epidemic wave by fitting a spatiotemporal regression model.FindingsFrom Sept 28, 2016, to March 12, 2018, 1 103 683 suspected cholera cases (attack rate 3·69%) and 2385 deaths (case fatality risk 0·22%) were reported countrywide. The epidemic consisted of two distinct waves with a surge in transmission in May, 2017, corresponding to a median Rt of more than 2 in 13 of 23 governorates. Microbiological analyses suggested that the same Vibrio cholerae O1 Ogawa strain circulated in both waves. We found a positive, non-linear, association between weekly rainfall and suspected cholera incidence in the following 10 days; the relative risk of cholera after a weekly rainfall of 25 mm was 1·42 (95% CI 1·31–1·55) compared with a week without rain.InterpretationOur analysis suggests that the small first cholera epidemic wave seeded cholera across Yemen during the dry season. When the rains returned in April, 2017, they triggered widespread cholera transmission that led to the large second wave. These results suggest that cholera could resurge during the ongoing 2018 rainy season if transmission remains active. Therefore, health authorities and partners should immediately enhance current control efforts to mitigate the risk of a new cholera epidemic wave in Yemen.FundingHealth Authorities of Yemen, WHO, and Médecins Sans Frontières.

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BackgroundAlmost two-thirds of refugees, internally displaced persons, returnees and other persons affected by humanitarian emergencies live in malaria endemic regions. Malaria remains a significant threat to the health of these populations.MethodsData on malaria incidence and mortality were analyzed from January 2006 to December 2009 from the United Nations High Commissioner for Refugees Health Information System database collected at sites in Burundi, Chad, Cameroon, Ethiopia, Kenya, Sudan, Tanzania, Thailand, and Uganda. Data from three countries during 2006 and 2007, and all nine countries from 2008 to 2009, were used to describe trends in malaria incidence and mortality. Monthly counts of malaria morbidity and mortality were aggregated into an annual country rate averaged over the study period.ResultsAn average of 1.18 million refugees resided in 60 refugee sites within nine countries with at least 50 cases of malaria per 1000 refugees during the study period 2008-2009. The highest incidence of malaria was in refugee sites in Tanzania, where the annual incidence of malaria was 399 confirmed cases per 1,000 refugees and 728 confirmed cases per 1,000 refugee children younger than five years. Malaria incidence in children younger than five years of age, based on the sum of confirmed and suspected cases, declined substantially at sites in two countries between 2006 and 2009, but a slight increase was reported at sites within four of seven countries between 2008 and 2009. Annual malaria mortality rates were highest in sites in Sudan (0.9 deaths per 1,000 refugees), Uganda and Tanzania (0.7 deaths per 1000 refugees each). Malaria was the cause of 16% of deaths in refugee children younger than five years of age in all study sites.ConclusionsThese findings represent one of the most extensive reports on malaria among refugees in post-emergency sites. Despite declines in malaria incidence among refugees in several countries, malaria remains a significant cause of mortality among children younger than five years of age. Further progress in malaria control, both within and outside of post-emergency sites, is necessary to further reduce malaria incidence and mortality among refugees and achieve global goals in malaria control and elimination.

BackgroundUnited Nations High Commissioner for Refugees (UNHCR) refugee camps are located predominantly in rural areas of Africa and Asia in protracted or post-emergency contexts. Recognizing the importance of malaria, pneumonia and diarrheal diseases as major causes of child morbidity and mortality in refugee camps, we analyzed data from the UNHCR Health Information System (HIS) to estimate incidence and risk factors for these diseases in refugee children younger than five years of age.MethodsData from 90 UNHCR camps in 16 countries, including morbidity, mortality, health services and refugee health status, were obtained from the UNHCR HIS for the period January 2006 to February 2010. Monthly camp-level data were aggregated to yearly estimates for analysis and stratified by location in Africa (including Yemen) or Asia. Poisson regression models with random effects were constructed to identify factors associated with malaria, pneumonia and diarrheal diseases. Spatial patterns in the incidence of malaria, pneumonia and diarrheal diseases were mapped to identify regional heterogeneities.ResultsMalaria and pneumonia were the two most common causes of mortality, with confirmed malaria and pneumonia each accounting for 20% of child deaths. Suspected and confirmed malaria accounted for 23% of child morbidity and pneumonia accounted for 17% of child morbidity. Diarrheal diseases were the cause of 7% of deaths and 10% of morbidity in children under five. Mean under-five incidence rates across all refugee camps by region were: malaria [Africa 84.7 cases/1000 U5 population/month (95% CI 67.5-102.0), Asia 2.2/1000/month (95% CI 1.4-3.0)]; pneumonia [Africa 59.2/1000/month (95% CI 49.8-68.7), Asia 254.5/1000/month (95% CI 207.1-301.8)]; and diarrheal disease [Africa 35.5/1000/month (95% CI 28.7-42.4), Asia 69.2/1000/month (95% CI 61.0-77.5)]. Measles was infrequent and accounted for a small proportion of child morbidity (503 cases, < 1%) and mortality (6 deaths, < 1%).ConclusionsAs in stable settings, pneumonia and diarrhea are important causes of mortality among refugee children. Malaria remains a significant cause of child mortality in refugee camps in Africa and will need to be addressed as part of regional malaria control and elimination efforts. Little is known of neonatal morbidity and mortality in refugee settings, and neonatal deaths are likely to be under-reported. Global measles control efforts have reduced the incidence of measles among refugee children.