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Many epidemic-prone infectious diseases present challenges that the current West African Ebola outbreak brings into sharp relief. Specifically, the urgency to evaluate vaccines, initially limited vaccine supplies, and large and unpredictable spatial and temporal fluctuations in incidence have presented huge logistical, ethical, and statistical challenges to trial design.

Supplementary immunization activities are crucial to reduce the number of susceptible children., Despite high reported coverage for routine and supplementary immunization, in 2010 in Malawi, a large measles outbreak occurred that comprised 134,000 cases and 304 deaths. Although the highest attack rates were for young children (2.3%, 7.6%, and 4.5% for children 15 years of age were highly affected (1.0% and 0.4% for persons 15–19 and >19 years, respectively; 28% of all cases). A survey in 8 districts showed routine coverage of 95.0% for children 12–23 months; 57.9% for children 9–11 months; and 60.7% for children covered during the last supplementary immunization activities in 2008. Vaccine effectiveness was 83.9% for 1 dose and 90.5% for 2 doses. A continuous accumulation of susceptible persons during the past decade probably accounts for this outbreak. Countries en route to measles elimination, such as Malawi, should improve outbreak preparedness. Timeliness and the population chosen are crucial elements for reactive campaigns.

Between July and December 2002, we undertook a hospital-based case-control study to identify risk factors associated with typhoid fever in Son La province, northern Vietnam. Among 617 suspected cases, 90 cases of typhoid fever were confirmed by blood or stool culture. One hundred and eighty controls (neighbours of typhoid cases matched for gender and age) were chosen. Participants were interviewed at home using a standardized questionnaire. Seventy-five per cent of cases were aged 10-44 years. No cases in patients aged less than 5 years were recorded in this study. In a conditional logistic regression analysis recent contact with a typhoid patient (OR = 3.3, 95% CI 1.7-6.2, P < 0.001), no education (OR = 2.0, 95% CI 1.0-3.7, P = 0.03) and drinking untreated water (OR = 3.9, 95% CI 2.0-7.5, P < 0.001) were independently associated with typhoid fever. Improving quality of drinking water must be a priority and health education strategies targeted at individuals with no schooling, and contacts of patients, would be expected to decrease the burden of typhoid fever.

Background Global deaths from measles have decreased notably in past decades, due to both increases in immunization rates and decreases in measles case fatality ratios (CFRs). While some aspects of the reduction in measles mortality can be monitored through increases in immunization coverage, estimating the level of measles deaths (in absolute terms) is problematic, particularly since incidence-based methods of estimation rely on accurate measures of measles CFRs. These ratios vary widely by geographic and epidemiologic context and even within the same community from year-to-year. Methods To understand better the variations in CFRs, we reviewed community-based studies published between 1980 and 2008 reporting age-specific measles CFRs. Results The results of the search consistently document that measles CFRs are highest in unvaccinated children under age 5 years; in outbreaks; the lowest CFRs occur in vaccinated children regardless of setting. The broad range of case and death definitions, study populations and geography highlight the complexities in extrapolating results for global public health planning. Conclusions Values for measles CFRs remain imprecise, resulting in continued uncertainty about the actual toll measles exacts.

Background A large poliomyelitis outbreak occurred in 2010 in the Republic of Congo. This paper describes the demographic and clinical characteristics of poliomyelitis cases and their outcomes following physiotherapy. Findings Demographic and clinical data were collected on 126 individuals between November 23, 2010 and March 23, 2011. The male/female ratio was 2.5 and the median age was 19 years (IQR: 13.5-23). The most severe forms of the disease were more common in older patients, 81 of the 126 patients (64.3%) had multiple evaluations of muscle strength. Among patients with multiple evaluations, 38.1% had improved strength at final evaluation, 48.3% were stable and 13.6% had decreased strength. Conclusions Most acute poliomyelitis patients receiving physiotherapy had improved or stable muscle strength at their final evaluation. These descriptive results highlight the need for further research into the potential benefits of physiotherapy in polio affected patients.

On November 4, 2010, the Republic of the Congo declared a poliomyelitis outbreak. A cross-sectional survey in Pointe-Noire showed poor sanitary conditions and low vaccination coverage (55.5%), particularly among young adults. Supplementary vaccination should focus on older age groups in countries with evidence of immunity gaps.

Background. A measles outbreak occurred in Maroua, Cameroon, from January 2008 to April 2009. In accordance with recent World Health Organization guidelines, an outbreak-response immunization (ORI) was conducted in January 2009. The aim of this study was to investigate the causes of the epidemic in order to guide vaccination strategies. Methods. We performed a stratified household-based survey using cluster sampling to determine measles vaccination coverage in children aged 9 months to 15 years. We defined 3 strata based on measles incidence. Next, we performed a case–control study to measure vaccine effectiveness (VE). Cases were obtained from health center registries. Controls were selected among respondents to the coverage survey. Results. The vaccination-coverage survey included 2963 children in total. The overall routine vaccination coverage was 74.1% (95% confidence interval [CI]: 70.0%–78.3%). Measles incidence was inversely proportional to routine vaccination coverage, with high incidence associated with coverage of 71% and low incidence associated with coverage of 84%. The overall VE was 94% (95% CI, 86.7%–97.4%). After the ORI in January 2009, the coverage was .90% in all strata and measles incidence declined rapidly. Discussion. Our results confirm that insufficient vaccination coverage was the main reason for this epidemic. The ORI conducted in January 2009 contributed both to control the epidemic and to increase the vaccination coverage to desirable levels.

Background. Measles caused mortality in .164,000 children in 2008, with most deaths occurring during outbreaks. Nonetheless, the impact and desirability of conducting measles outbreak response immunization (ORI) in middle- and low-income countries has been controversial. World Health Organization guidelines published in 1999 recommended against ORI in such settings, although recently these guidelines have been reversed for countries with measles mortality reduction goals. Methods. We searched literature published during 1995–2009 for papers reporting on measles outbreaks. Papers identified were reviewed by 2 reviewers to select those that mentioned ORI. World Bank classification of country income was used to identify reports of outbreaks in middle- and low-income countries. Results. We identified a total of 485 articles, of which 461 (95%) were available. Thirty-eight of these papers reported on a total of 38 outbreaks in which ORI was used. ORI had a clear impact in 16 (42%) of these outbreaks. In the remaining outbreaks, we were unable to independently assess the impact of ORI. Conclusions. These findings generally support ORI in middle- and low-income countries. However, the decision to conduct ORI and the nature and extent of the vaccination response need to be made on a case-by-case basis.

Measles, a highly infectious vaccine-preventable viral disease, is potentially fatal. Historically, measles case-fatality ratios (CFRs) have been reported to vary from 0.1% in the developed world to as high as 30% in emergency settings. Estimates of the global burden of mortality from measles, critical to prioritizing measles vaccination among other health interventions, are highly sensitive to the CFR estimates used in modeling; however, due to the lack of reliable, up-to-date data, considerable debate exists as to what CFR estimates are appropriate to use. To determine current measles CFRs in high-burden settings without vital registration we have conducted six retrospective measles mortality studies in such settings. This paper examines the methodological challenges of this work and our solutions to these challenges, including the integration of lessons from retrospective all-cause mortality studies into CFR studies, approaches to laboratory confirmation of outbreaks, and means of obtaining a representative sample of case-patients. Our experiences are relevant to those conducting retrospective CFR studies for measles or other diseases, and to those interested in all-cause mortality studies.

Background: Shigella dysenteriae type 1 (Sd1) is a cause of major dysentery outbreaks, particularly among children and displaced populations in tropical countries. Although outbreaks continue, the characteristics of such outbreaks have rarely been documented. Here, we describe the Sd1 outbreaks occurring between 1993 and 1995 in 11 refugee settlements in Rwanda, Tanzania and Democratic Republic of the Congo (DRC). We also explored the links between the different types of the camps and the magnitude of the outbreaks. Methodology/Principal Findings: Number of cases of bloody diarrhea and deaths were collected on a weekly basis in 11 refugee camps, and analyzed retrospectively. Between November 1993 and February 1995, 181,921 cases of bloody diarrhea were reported. Attack rates ranged from 6.3% to 39.1% and case fatality ratios (CFRs) from 1.5% to 9.0% (available for 5 camps). The CFRs were higher in children under age 5. In Tanzania where the response was rapidly deployed, the mean attack rate was lower than in camps in the region of Goma without an immediate response (13.3% versus 32.1% respectively). Conclusions/Significance: This description, and the areas where data is missing, highlight both the importance of collecting data in future epidemics, difficulties in documenting outbreaks occurring in complex emergencies and most importantly, the need to assure that minimal requirements are met. © 2009 Kernéis et al.

Introduction On 4 November 2010, the Ministry of Health of the Republic of Congo declared a poliomyelitis outbreak in Pointe-Noire, the eastern economic capital. We conducted an outbreak investigation to describe the epidemic and estimate vaccination coverage to better understand virus spread. Methods We collected clinical, demographic and geographic data about cases and vaccination policies from local health authorities. Cases were defined as residents of Pointe-Noire of any age, diagnosed with acute flaccid paralysis since 1 October 2010. We implemented a cross-sectional survey in a socially heterogeneous affected neighbourhood (representing 9.5% of the city population), selected from the Loandjili district (highest district attack rate: 71.6 cases per 100 000) following expert consultation. Results From 1 October to 20 December 2010, 446 cases of acute flaccid paralysis were reported to health authorities (case fatality ratio: 41.3%). Males accounted for 68% of the cases, and 57.4% were between 15 and 24 years of age. Vaccination coverage in the surveyed population for one or more doses of oral polio vaccine was 55.5% on average and decreased with age to 33.5% for individuals older than 30. Sanitary conditions were poor to medium with latrines commonly shared between households (57.4%). Conclusion Poor vaccination coverage led to a large susceptible population, particularly in young adults and spread was further facilitated by poor sanitary conditions. Moreover, polio causes more severe clinical symptoms among older age groups, which explains the high case-fatality ratio. To prevent similar outbreaks in other countries, supplementary vaccination activities should punctually target older age groups.

Background Lassa fever is a viral hemorrhagic fever endemic in West Africa. The reservoir host of the virus is a multimammate rat, Mastomys natalensis. Prevalence estimates of Lassa virus antibodies in humans vary greatly between studies, and the main modes of transmission of the virus from rodents to humans remain unclear. We aimed to (i) estimate the prevalence of Lassa virus–specific IgG antibodies (LV IgG) in the human population of a rural area of Guinea, and (ii) identify risk factors for positive LV IgG. Methods and Findings A population-based cross-sectional study design was used. In April 2000, all individuals one year of age and older living in three prefectures located in the tropical secondary forest area of Guinea (Gueckedou, Lola and Yomou) were sampled using two-stage cluster sampling. For each individual identified by the sampling procedure and who agreed to participate, a standardized questionnaire was completed to collect data on personal exposure to potential risk factors for Lassa fever (mainly contact with rodents), and a blood sample was tested for LV IgG. A multiple logistic regression model was used to determine risk factors for positive LV IgG. A total of 1424 subjects were interviewed and 977 sera were tested. Prevalence of positive LV Ig was of 12.9% [10.8%–15.0%] and 10.0% [8.1%–11.9%] in rural and urban areas, respectively. Two risk factors of positive LV IgG were identified: to have, in the past twelve months, undergone an injection (odds ratio [OR] = 1.8 [1.1–3.1]), or lived with someone displaying a haemorrhage (OR = 1.7 [1.1–2.9]). No factors related to contacts with rats and/or mice remained statistically significant in the multivariate analysis. Conclusions Our study underlines the potential importance of person-to-person transmission of Lassa fever, via close contact in the same household or nosocomial exposure., Author Summary Lassa fever is a viral haemorrhagic fever endemic in West Africa, mainly transmitted to humans by multimammate rats. Several modes of virus transmission are suspected: aerosolisation of the virus, contact with infected rodent excreta, and consumption of rodent meat. Person-to-person transmission also occurs via contact with body fluids of infected persons (blood, urine) and is responsible for numerous outbreaks, mostly in healthcare facilities. Our objective was to precisely describe risk factors for Lassa fever in both rural and urban communities of forest Guinea. For each participant, a standardized questionnaire was completed and a blood sample tested for Lassa virus antibodies. A total of 1424 subjects were interviewed and 977 blood samples tested. The prevalence of Lassa virus antibodies was estimated at 12.9% and 10.0% in rural and urban areas, respectively. The two risk factors were: to have, in the past twelve months, undergone an injection, or lived with someone displaying a haemorrhage. Contrary to our expectation, no factors related to contact with rodents were identified. It is still probable that transmission occurs via indirect contact between rodents and humans in households, but our results highlight the importance of person-to-person transmission via close contact and nosocomial exposure.

In July 1994, 500,000 to 800,000 Rwandans crossed the border into the North Kivu region of Zaire (now called the Democratic Republic of the Congo, DRC). During the first month after the influx, almost 50,000 refugees died; cholera was a major contributor ( 1 ).

Background Although measles mortality has declined dramatically in Sub-Saharan Africa, measles remains a major public health problem in countries like the Democratic Republic of Congo (DRC). Here, we describe the large measles epidemic that occurred in the Democratic Republic of Congo between 2010 and 2013 using data from the national surveillance system as well as vaccine coverage surveys to provide a snapshot of the epidemiology of measles in DRC. Methods Standardized national surveillance data were used to describe measles cases from 2010 to 2013. Attack rates and case fatality ratios were calculated and the temporal and spatial evolution of the epidemic described. Data on laboratory confirmation and vaccination coverage surveys as a part of routine program monitoring are also presented. Findings Between week 1 of 2010 and week 45 of 2013, a total of 294,455 cases and 5,045 deaths were reported. The cumulative attack rate (AR) was 0.4%. The Case Fatality Ratio (CFR) was 1.7% among cases reported in health structures through national surveillance. A total of 186,178 cases (63%) were under 5 years old, representing an estimated AR of 1.4% in this age group. Following the first mass vaccination campaigns, weekly reported cases decreased by 21.5%. Results of post-vaccination campaign coverage surveys indicated sub-optimal (under 95%) vaccination coverage among children surveyed. Conclusions The data reported here highlight the need to seek additional means to reinforce routine immunization as well as ensure the timely implementation of Supplementary Immunization Activities to prevent large and repeated measles epidemics in DRC. Although reactive campaigns were conducted in response to the epidemic, strategies to ensure that children are vaccinated in the routine system remains the foundation of measles control.