Heterogeneity in social and epidemiological factors determines the risk of measles outbreaks.
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ABSTRACT:
SUBMITTER: Bosetti P
PROVIDER: S-EPMC7720222 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:BackgroundAge-stratified serologic surveys provide insight into the gaps of measles-specific immunity as well as estimates of the age-specific seroprevalence. The aim of this study was to describe the measles sero-epidemiology in Vojvodina before the occurrence of outbreak in 2017/18 and to discuss preventive measures for potential future epidemics.MethodsA seroprevalence study was conducted from April 2015 to June 2017 on serum bank of 3199 residual samples. Study was performed prior to the last measles outbreak in Vojvodina that occurred between 12th November 2017 and 30th June 2018. Measles-specific IgG antibodies were determined using an indirect chemiluminescent immunoassay (CLIA).ResultsMedian age of enrolled participants was 20 years (IQR 11-37). Overall, 86.9% serum samples were seropositive. The highest proportion of measles seronegativity was observed in children aged 12-23 months of age and in adults aged 20-39 years (56.1% and 18.5%, respectively). Prevalence of measles seronegativity above WHO target levels susceptibility was observed in the following age groups: 2, 7, 13, 15, and among all adults aged between 20 and 49 years. Out of total measles outbreak cases (177), there were 91 (51.4%) participants aged 20-39 years. A significant positive correlation was observed between measles seronegativity and the number of reported measles cases aged ≥ 12 months (r = 0.4675, p = 0.0213).ConclusionsIn order to prevent new outbreaks and achieve the elimination of measles in Vojvodina, the vaccination coverage of both measles-mumps-rubella (MMR1 and MMR2) vaccines needs to be improved and sustained. Educational campaigns for the improvement of acceptance and timely vaccination with vaccine against measles among doctors and the general population are crucial. Our results indicate possible gap in measles protection in adults born during implementation of one dose of measles vaccine and prioritize supplementary immunization activities targeting adults in Vojvodina, Serbia.
| S-EPMC6508608 | biostudies-literature
Project description:BackgroundVaccination programmes to prevent outbreaks after introductions of infectious people aim to maintain the average number of secondary infections per infectious person at one or less. We aimed to assess heterogeneity in vaccine uptake and other characteristics that, together with non-random mixing, could increase this number and to evaluate strategies that could mitigate their impact.MethodsBecause most US children attend elementary school in their own neighbourhoods, surveys of children entering elementary school (age 5 years before Sept 1) allow assessment of spatial heterogeneity in the proportion of children immune to vaccine-preventable diseases. We used data from a 2008 school-entry survey by the Immunization Division of the California Department of Public Health to obtain school addresses; numbers of students enrolled; proportions of enrolled students who had received one or two doses of the measles, mumps, and rubella (MMR) vaccine; and proportions with medical or personal-belief exemptions. Using a mixing model suitable for spatially-stratified populations, we projected the expected numbers of secondary infections per infectious person for measles, mumps, and rubella. We also mapped contributions to this number for measles in San Diego County's 638 elementary schools and its largest district, comprising 200 schools (31%). We then modelled the effect on measles' realised reproduction number (RV) of the following plausible interventions: vaccinating all children with personal-belief exemptions, increasing uptake by 10% to 50% in all low-immunity schools (<90% of students immune) or in only influential (effective daily contact rates >3 or contacts inter-school >30%) low-immunity schools, and increasing private school uptake to the public school average.FindingsIn 2008, 39 132 children began elementary school in San Diego County, CA, USA. At entry to school, 97% had received at least one dose of the MMR vaccine, with 2·5% having personal-belief exemptions. We note substantial heterogeneity in immunity throughout the county. Although the average population immunities for measles, mumps, and rubella (92%, 87%, 92%) were similar to the population-immunity thresholds in homogeneous, randomly-mixing populations (91%, 88%, 76%), after accounting for heterogeneity and non-random mixing, the basic reproduction numbers increased by 70%, meaning that introduced pathogens could cause outbreaks. The impact of our modelled interventions ranged from negligible to a nearly complete reduction in the outbreak potential of measles. The most effective intervention to lower the realised reproduction number (RV 3·39) was raising immunity by 50% in 114 schools with low immunity (RV 1·02), but raising immunity by this level in only influential, low-immunity schools also was effective (RV 2·02). The effectiveness of vaccinating the 972 children with personal-belief exemptions was similar to that of targeting all low-immunity schools (RV 1·11). Targeting only private schools had little effect.InterpretationOur findings suggest that increasing vaccine uptake could prevent outbreaks such as that of measles in San Diego in 2008. Vaccinating children with personal-belief exemptions was one of the most effective interventions that we modelled, but further research on mixing in heterogeneous populations is needed.FundingNone.
| S-EPMC5859952 | biostudies-literature
Project description:Though largely controlled in developed countries, measles remains a major global public health issue. Regional and local transmission patterns are rooted in human mixing behaviour across spatial scales. Identifying spatial interactions that contribute to recurring epidemics helps define and predict outbreak patterns. Using spatially explicit reported cases from measles outbreaks in Niger, we explored how regional variations in movement and contact patterns relate to patterns of measles incidence. Because we expected to see lower rates of re-introductions in small, compared to large, populations, we measured the population-size corrected proportion of weeks with zero cases across districts to understand relative rates of measles re-introductions. We found that critical elements of spatial disease dynamics in Niger are agricultural seasonality, transnational contact clusters, and roads networks that facilitate host movement and connectivity. These results highlight the need to understand local patterns of seasonality, demographic characteristics, and spatial heterogeneities to inform vaccination policy.
| S-EPMC4756478 | biostudies-literature
Project description:BackgroundAlthough a universal vaccine is available and Ethiopia is working outstandingly towards measles elimination, a recurrent measles outbreak has occurred each year in different parts of the country. Therefore, understanding the epidemiology of measles cases, the incidence of confirmed measles virus cases and related risk factors is crucial. Here, we conducted a systematic review and meta-analysis to summarize information regarding the epidemiology, measles incidence rate and risk factors for national measles infections occurring in the past two decades, from 2000 to 2023.MethodsData from electronic databases, including PubMed, African Journal Online, WHO databases and Google Scholars, were searched to identify studies describing measles outbreaks, incidence rates and associated factors in Ethiopia that occurred between 2000 and 2023. Important basic information was extracted in an Excel spreadsheet and imported into Comprehensive Meta-analysis Software version 3 to evaluate the associations between measles outbreaks and different risk factors. We pooled the odds ratios (ORs) and 95% confidence intervals (CIs) for every included risk factor to evaluate the associations with measles outbreaks.ResultsWe included 36 studies involving 132,502 patients with confirmed measles cases in Ethiopia. The results of this systematic review and meta-analysis revealed that measles outbreaks were more frequently reported in the Oromia region (73,310 (33.1%)), followed by the Southern Nation Nationalities of Ethiopia region (29,057 (13.4%)). The overall pooled analysis indicated that the prevalence of measles susceptibility was 67.5% (95% CI: 67.3-67.8%), with an I2 of 99.86% and a p value for heterogeneity < 0.0001. The non-vaccinated status of the children, their contact history with measles cases, their travel history, the presence of cases in family or neighbors, and malnourished patients were identified as factors associated with the high prevalence and recurrent measles infections in Ethiopia.ConclusionThe results of this systematic review and meta-analysis indicated that the pooled prevalence of measles infection was high, which is a public health concern in Ethiopia. Thus, strengthening healthcare services, regular vaccination campaigns, and the integration of health education activities with other services may decrease the incidence rate.
| S-EPMC11370270 | biostudies-literature
Project description:PurposeIn 2012, Cameroon experienced a large measles outbreak of over 14,000 cases. To determine the spatio-temporal dynamics of measles transmission in Cameroon, we analyzed weekly case data collected by the Ministry of Health.MethodsWe compared several multivariate time-series models of population movement to characterize the spatial spread of measles in Cameroon. Using the best model, we evaluated the contribution of population mobility to disease transmission at increasing geographic resolutions: region, department, and health district.ResultsOur spatio-temporal analysis showed that the power law model, which accounts for long-distance population movement, best represents the spatial spread of measles in Cameroon. Population movement between health districts within departments contributed to 7.6% (range: 0.4%-13.4%) of cases at the district level, whereas movement between departments within regions contributed to 16.0% (range: 1.3%-23.2%) of cases. Long-distance movement between regions contributed to 16.7% (range: 0.1%-59.0%) of cases at the region level, 20.1% (range: 7.1%-30.0%) at the department level, and 29.7% (range: 15.3%-47.6%) at the health district level.ConclusionsPopulation long-distance mobility is an important driver of measles dynamics in Cameroon. These findings demonstrate the need to improve our understanding of the roles of population mobility and local heterogeneity of vaccination coverage in the spread and control of measles in Cameroon.
| S-EPMC7056523 | biostudies-literature
Project description:Opportunist saprotrophic pathogens differ from obligatory pathogens due to their capability in host-independent growth in environmental reservoirs. Thus, the outside-host environment potentially influences host-pathogen dynamics. Despite the socio-economical importance of these pathogens, theory on their dynamics is practically missing. We analyzed a novel epidemiological model that couples outside-host density-dependent growth to host-pathogen dynamics. Parameterization was based on columnaris disease, a major hazard in fresh water fish farms caused by saprotrophic Flavobacterium columnare. Stability analysis and numerical simulations revealed that the outside-host growth maintains high proportion of infected individuals, and under some conditions can drive host extinct. The model can show stable or cyclic dynamics, and the outside-host growth regulates the frequency and intensity of outbreaks. This result emerges because the density-dependence stabilizes dynamics. Our analysis demonstrates that coupling of outside-host growth and traditional host-pathogen dynamics has profound influence on disease prevalence and dynamics. This also has implications on the control of these diseases.
| S-EPMC3511454 | biostudies-other
Project description:Bronchopulmonary dysplasia (BPD) is the chronic lung disease of preterm infants and still represents a major burden of prematurity. Several clinical risk factors for the onset of the disease are already known. In addition, some candidate genes have recently been identified. We set out to determine clinical as well as genetic risk factors for the development of BPD in the German population. 155 infants born with a gestational age < or = 28 at the tertiary neonatal Centre, Freiburg, were recruited. Clinical data were recorded from hospital charts. 47 children developed moderate or severe BPD. For genetic analyses, 37 polymorphisms within sixteen genes were genotyped on all children. The strongest epidemiological risk factor for BPD was birth weight, followed by low gestational age. Genetic association was detected with single polymorphisms within Tumour necrosis factor alpha, Toll like receptor 10 and vascular endothelial growth factor. The former two genes showed also association with BPD in haplotype analyses. In conclusion, association of BPD was far more convincingly found with a few clinical factors than with genetic polymorphisms. This underscores the genetic complexity of the disease. Furthermore, the identification of predisposing genetic polymorphisms might be hampered by the complex interaction between clinical and genetic factors.
| S-EPMC3835287 | biostudies-other
Project description:ImportanceVaccine exemptions, which allow unvaccinated children to attend school, have increased by a factor of 28 since 2003 in Texas. Geographic clustering of unvaccinated children facilitates the spread of measles introductions, but the potential size of outbreaks is unclear.ObjectiveTo forecast the range of measles outbreak sizes in each metropolitan area of Texas at 2018 and future reduced school vaccination rates.Design, setting, and participantsAn agent-based decision analytical model using a synthetic population of Texas, derived from the 2010 US Census, was used to simulate measles transmission in the Texas population. Real schools were represented in the simulations, and the 2018 vaccination rate of each real school was applied to a simulated hypothetical equivalent. Single cases of measles were introduced, daily activities and interactions were modeled for each population member, and the number of infections over the course of 9 months was counted for 1000 simulated runs in each Texas metropolitan area.InterventionsTo determine the outcomes of further decreases in vaccination coverage, additional simulations were performed with vaccination rates reduced by 1% to 10% in schools with populations that are currently undervaccinated.Main outcomes and measuresExpected distributions of outbreak sizes in each metropolitan area of Texas at 2018 and reduced vaccination rates.ResultsAt 2018 vaccination rates, the median number of cases in large metropolitan areas was typically small, ranging from 1 to 3 cases, which is consistent with outbreaks in Texas 2006 to 2017. However, the upper limit of the distribution of plausible outbreaks (the 95th percentile, associated with 1 in 20 measles introductions) exceeded 400 cases in both the Austin and Dallas metropolitan areas, similar to the largest US outbreaks since measles was eliminated in 2000. Decreases in vaccination rates in schools with undervaccinated populations in 2018 were associated with exponential increases in the potential size of outbreaks: a 5% decrease in vaccination rate was associated with a 40% to 4000% increase in potential outbreak size, depending on the metropolitan area. A mean (SD) of 64% (11%) of cases occurred in students for whom a vaccine had been refused, but a mean (SD) of 36% (11%) occurred in others (ie, bystanders).Conclusions and relevanceThis study suggests that vaccination rates in some Texas schools are currently low enough to allow large measles outbreaks. Further decreases are associated with dramatic increases in the probability of large outbreaks. Limiting vaccine exemptions could be associated with a decrease in the risk of large measles outbreaks.
| S-EPMC6707017 | biostudies-literature
Project description:BackgroundSince the first recognition of the pandemic characteristics of SARS-CoV-2 infection, and before substantial case fatality data were available worldwide, public health agencies warned the public about the increased dangers of SARS-CoV-2 to persons with a variety of underlying physical conditions, many of which are more commonly found in persons over 50 years of age or in certain ethnic groups.ObjectiveTo investigate the statistical rather than the physiological basis in support of the abovementioned warnings, this study examines correlations globally on a nation-by-nation basis between the statistical data concerning COVID-19 fatalities and the statistics of potential comorbidities that may influence the severity of infection.MethodsThis study considers the statistics describing the populations of the 99 countries with the greatest numbers of SARS-CoV-2 infections at the time of the data cutoff. As national compilations of direct measures of immune system strength are not publicly available, the frequency of fatalities in those countries due to a variety of serious diseases is used as a proxy for the susceptibility of those populations to those same diseases.ResultsThe analysis produces plots and calculations of correlations and cross-correlations of COVID-19 case fatality rates and the risks of other potential cofactors. It exposes some reasons that may underlie the degree to which advanced age increases the risk of mortality of infection with SARS-CoV-2. In contrast with the strong influences of comorbidities on the seriousness of consequences of influenzas and their associated pneumonias, the correlations of the same set of risk factors with SARS-CoV-2 infection are considerably weaker. The general characteristics of the observed correlations strengthened through 3 cycles of analysis, starting in September 2020. The strongest correlations were with chronic kidney disease and coronary disease (approximately 0.28 and 0.20, respectively).ConclusionsThis study confirms early clinical observations that infection with SARS-CoV-2 presents an increased risk to persons over the age of 65 years. It does not support the suggestions presented by government agencies early in the pandemic that the risks are much greater for persons with certain common potential comorbidities.
| S-EPMC8404263 | biostudies-literature
Project description:In 2013, a resurgence of measles occurred in Beijing, China. The outbreaks occurred among adults and were associated with endemic genotype H1 and imported genotype D8 viruses. Migrant workers were disproportionately represented in the outbreaks; thus, vaccinating such workers against measles may be an effective strategy toward the elimination of this disease.
| S-EPMC4344261 | biostudies-literature