Abdinasir Abubakar

Effectiveness of one dose of oral cholera vaccine in response to an outbreak: a case-cohort study

BACKGROUND Oral cholera vaccines represent a new effective tool to fight cholera and are licensed as two-dose regimens with 2-4 weeks between doses. Evidence from previous studies suggests that a single dose of oral cholera vaccine might provide substantial direct protection against cholera. During a cholera outbreak in May, 2015, in Juba, South Sudan, the Ministry of Health, Médecins Sans Frontières, and partners engaged in the first field deployment of a single dose of oral cholera vaccine to enhance the outbreak response. We did a vaccine effectiveness study in conjunction with this large public health intervention. METHODS We did a case-cohort study, combining information on the vaccination status and disease outcomes from a random cohort recruited from throughout the city of Juba with that from all the cases detected. Eligible cases were those aged 1 year or older on the first day of the vaccination campaign who sought care for diarrhoea at all three cholera treatment centres and seven rehydration posts throughout Juba. Confirmed cases were suspected cases who tested positive to PCR for Vibrio cholerae O1. We estimated the short-term protection (direct and indirect) conferred by one dose of cholera vaccine (Shanchol, Shantha Biotechnics, Hyderabad, India). FINDINGS Between Aug 9, 2015, and Sept 29, 2015, we enrolled 87 individuals with suspected cholera, and an 898-person cohort from throughout Juba. Of the 87 individuals with suspected cholera, 34 were classified as cholera positive, 52 as cholera negative, and one had indeterminate results. Of the 858 cohort members who completed a follow-up visit, none developed clinical cholera during follow-up. The unadjusted single-dose vaccine effectiveness was 80·2% (95% CI 61·5-100·0) and after adjusting for potential confounders was 87·3% (70·2-100·0). INTERPRETATION One dose of Shanchol was effective in preventing medically attended cholera in this study. These results support the use of a single-dose strategy in outbreaks in similar epidemiological settings. FUNDING Médecins Sans Frontières.

The First Use of the Global Oral Cholera Vaccine Emergency Stockpile: Lessons from South Sudan

Andrew Azman and colleagues describe their experience of deploying >250,000 doses of oral cholera vaccine in South Sudan in 2014

Visceral leishmaniasis outbreak in South Sudan 2009-2012: epidemiological assessment and impact of a multisectoral response.

The humanitarian situation in South Sudan is dire, with over two million returnees since 2005 and another 300,000 expected to return by the end of 2013. In 2012, 170,000 refugees settled in five camps in Unity and Upper Nile states, endemic areas of visceral leishmaniasis (VL) (Office for the Coordination of Humanitarian Affairs Sudan Humanitarian Update 1st Quarter 2012). VL in South Sudan is endemic in four states, namely Upper Nile, Unity, Jonglei, and Eastern Equatoria, where 2.7 million people in 28 counties are considered to be at risk. It is an anthroponosis caused by Leishmania donovani, and the vectors are Phlebotomus orientalis and P. martini. South Sudan is suffering from recurrent epidemics in areas previously considered to be nonendemic [1]. VL in South Sudan was first described in a child from Bahr-el-Ghazal in 1904 [2]. Since then, outbreaks have been reported in several different areas, namely Jonglei state in the 1930s and 60s [3], [4], the former Blue Nile province in the 50s [5], and Unity state (formerly Western Upper Nile) in the 80s, until by the 90s it was claimed that almost one-third of the population had been affected between 1984 and 1994 [6]–[8]. In 1994 and in 2002 there were two further outbreaks in northern Jonglei and Eastern Upper Nile states, resulting in 17,000 cases reported. Since 2002, the number of cases reported has progressively decreased to reach 582 in 2008. From 2004 to 2008, an average of 1,756 cases were reported annually, although the actual number of cases was estimated to be between 7,400 and 14,200 cases [9]. Until 2004, VL treatment services were provided almost exclusively by Medecins Sans Frontieres-Holland (MSF-H), after which time part of the VL-treatment activities were handed over to the Southern Sudan Secretariat of Health. In addition to this, the World Health Organization (WHO) supported eight health facilities run by nongovernmental organizations (NGOs), and in 2009, that network was expanded to 12. Another VL outbreak was declared in 2009 and it is still ongoing. This publication provides a detailed report on the epidemiology of and the response to this outbreak.

Cholera epidemic in Yemen, 2016–18: an analysis of surveillance data

Summary Background In 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. Methods The 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. Findings From 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. Interpretation Our 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. Funding Health Authorities of Yemen, WHO, and Médecins Sans Frontières.

Population-Level Effect of Cholera Vaccine on Displaced Populations, South Sudan, 2014.

Following mass population displacements in South Sudan, preventive cholera vaccination campaigns were conducted in displaced persons camps before a 2014 cholera outbreak. We compare cholera transmission in vaccinated and unvaccinated areas and show vaccination likely halted transmission within vaccinated areas, illustrating the potential for oral cholera vaccine to stop cholera transmission in vulnerable populations.

Mapping the burden of cholera in sub-Saharan Africa and implications for control: an analysis of data across geographical scales

Summary Background Cholera remains a persistent health problem in sub-Saharan Africa and worldwide. Cholera can be controlled through appropriate water and sanitation, or by oral cholera vaccination, which provides transient (∼3 years) protection, although vaccine supplies remain scarce. We aimed to map cholera burden in sub-Saharan Africa and assess how geographical targeting could lead to more efficient interventions. Methods We combined information on cholera incidence in sub-Saharan Africa (excluding Djibouti and Eritrea) from 2010 to 2016 from datasets from WHO, Médecins Sans Frontières, ProMED, ReliefWeb, ministries of health, and the scientific literature. We divided the study region into 20 km × 20 km grid cells and modelled annual cholera incidence in each grid cell assuming a Poisson process adjusted for covariates and spatially correlated random effects. We combined these findings with data on population distribution to estimate the number of people living in areas of high cholera incidence (>1 case per 1000 people per year). We further estimated the reduction in cholera incidence that could be achieved by targeting cholera prevention and control interventions at areas of high cholera incidence. Findings We included 279 datasets covering 2283 locations in our analyses. In sub-Saharan Africa (excluding Djibouti and Eritrea), a mean of 141 918 cholera cases (95% credible interval [CrI] 141 538–146 505) were reported per year. 4·0% (95% CrI 1·7–16·8) of districts, home to 87·2 million people (95% CrI 60·3 million to 118·9 million), have high cholera incidence. By focusing on the highest incidence districts first, effective targeted interventions could eliminate 50% of the regions cholera by covering 35·3 million people (95% CrI 26·3 million to 62·0 million), which is less than 4% of the total population. Interpretation Although cholera occurs throughout sub-Saharan Africa, its highest incidence is concentrated in a small proportion of the continent. Prioritising high-risk areas could substantially increase the efficiency of cholera control programmes. Funding The Bill & Melinda Gates Foundation.

Immune Responses to an Oral Cholera Vaccine in Internally Displaced Persons in South Sudan

Despite recent large-scale cholera outbreaks, little is known about the immunogenicity of oral cholera vaccines (OCV) in African populations, particularly among those at highest cholera risk. During a 2015 preemptive OCV campaign among internally displaced persons in South Sudan, a year after a large cholera outbreak, we enrolled 37 young children (1–5 years old), 67 older children (6–17 years old) and 101 adults (≥18 years old), who received two doses of OCV (Shanchol) spaced approximately 3 weeks apart. Cholera-specific antibody responses were determined at days 0, 21 and 35 post-immunization. High baseline vibriocidal titers (>80) were observed in 21% of the participants, suggesting recent cholera exposure or vaccination. Among those with titers ≤80, 90% young children, 73% older children and 72% adults seroconverted (≥4 fold titer rise) after the 1st OCV dose; with no additional seroconversion after the 2nd dose. Post-vaccination immunological endpoints did not differ across age groups. Our results indicate Shanchol was immunogenic in this vulnerable population and that a single dose alone may be sufficient to achieve similar short-term immunological responses to the currently licensed two-dose regimen. While we found no evidence of differential response by age, further immunologic and epidemiologic studies are needed.

Burden of acute respiratory disease of epidemic and pandemic potential in the WHO Eastern Mediterranean Region: A literature review.

There are gaps in the knowledge about the burden of severe respiratory disease in the Eastern Mediterranean Region (EMR). This literature review was therefore conducted to describe the burden of epidemicand pandemic-prone acute respiratory infections (ARI) in the Region which may help in the development of evidence-based disease prevention and control policies. Relevant published and unpublished reports were identified from searches of various databases; 83 documents fulfilled the search criteria. The infections identified included: ARI, avian influenza A(H5N1), influenza A(H1N1)pdm09 and Middle East respiratory syndrome coronavirus (MERS-CoV) infection. Pneumonia and ARIs were leading causes of disease and death in the Region. Influenza A(H1N1) was an important cause of morbidity during the 2009 pandemic. This review provides a descriptive summary of the burden of acute respiratory diseases in the Region, but there still remains a lack of necessary data.

Middle East respiratory syndrome coronavirus: current knowledge and future considerations.

A literature review of publically available information was undertaken to summarize current understanding and gaps in knowledge about Middle East respiratory syndrome coronavirus (MERS-CoV), including its origin, transmission, effective control measures and management. Major databases were searched and relevant published papers and reports during 2012-2015 were reviewed. Of the 2520 publications initially retrieved, 164 were deemed relevant. The collected results suggest that much remains to be discovered about MERS-CoV. Improved surveillance, epidemiological research and development of new therapies and vaccines are important, and the momentum of recent gains in terms of better understanding of disease patterns should be maintained to enable the global community to answer the remaining questions about this disease.

Zika virus: no cases in the Eastern Mediterranean Region but concerns remain.

Following the WHO declaration on 1 February 2016 of a Public Health Emergency of International Concern (PHEIC) with regard to clusters of microcephaly and neurological disorders potentially associated with Zika virus, the WHO Regional Office for the Eastern Mediterranean conducted three rounds of emergency meetings to address enhancing preparedness actions in the Region. The meetings provided up-to-date information on the current situation and agreed on a set of actions for the countries to undertake to enhance their preparedness and response capacities to Zika virus infection and its complications. The most urgent action is to enhance both epidemiological and entomological surveillance between now and the coming rainy seasons in countries with known presence of Aedes mosquitoes. Zika virus like other vector-borne diseases poses a particular challenge to the countries because of their complex nature which requires multidisciplinary competencies and strong rapid interaction among committed sectors. WHO is working closely with partners and countries to ensure the optimum support is provided to the countries to reduce the risk of this newly emerged health threat.