Duration Of Outbreak Research Articles

Interhospital transmission of vancomycin-resistant Enterococcus faecium in Aomori, Japan

BackgroundSpread of vancomycin-resistant Enterococcus (VRE) is a global concern as a significant cause of healthcare-associated infections. A series of VRE faecium (VREf) outbreaks caused by clonal propagation due to interhospital transmission occurred in six general hospitals in Aomori prefecture, Japan.MethodsThe number of patients with VREf was obtained from thirty seven hospitals participating in the local network of Aomori prefecture. Thirteen hospitals performed active screening tests for VRE. Whole genome sequencing analysis was performed.ResultsThe total number of cases with VREf amounted to 500 in fourteen hospitals in Aomori from Jan 2018 to April 2021. It took more than three years for the frequency of detection of VRE to return to pre-outbreak levels. The duration and size of outbreaks differed between hospitals according to the countermeasures available at each hospital. Whole genome sequencing analysis indicated vanA-type VREf ST1421 for most samples from six hospitals.ConclusionsThis was the first multi-jurisdictional outbreak of VREf sequence type 1421 in Japan. In addition to strict infection control measures, continuous monitoring of VRE detection in local medical regions and smooth and immediate communication among hospitals are required to prevent VREf outbreaks.

Analysis of Epidemiological and Economic Impact of Foot-and-Mouth Disease Outbreaks in Four District Areas in Thailand.

Foot and mouth disease (FMD) is one of the most important infectious animal diseases impacting livestock production in Thailand. Despite a national vaccination program, FMD outbreaks are reported every year. We studied the epidemiological impacts of FMD outbreaks in four districts of Thailand between 2015 and 2016. Epidemiological data were collected from 193 FMD-affected dairy farms, 55 FMD-affected beef farms, and 25 FMD-affected pig farms. A significant difference in morbidity rates were observed between the dairy farms in the different areas, which could be explained by the differences in FMD outbreak management in each area. The morbidity rates in dairy and beef cattle also significantly differed between each animal age category, with the lowest morbidity rate observed in calves. Remarkably, vaccination was not significantly associated with the morbidity rate. In addition, the economic impact of FMD was calculated for 60 dairy farms in Muak Lek district. The economic losses were determined as the sum of milk production loss, mortality loss, additional labor costs, and veterinary service and medical costs, which averaged 56 USD per animal on the farm (ranging from 2 to 377 USD). Milk loss had the largest economic impact, although it varied substantially between farms. The farm size and outbreak duration were significantly associated with the total economic losses per farm. These results affirm the substantial epidemiological and economic impact of FMD on farms in Thailand, emphasizing the importance of FMD control.

Foodborne Illness Outbreak Severity Across Geographic and Supply Chain Contamination Locations in the United States, 2009–2019

ObjectivesIn 2009, the Centers for Disease Control and Prevention's National Outbreak Reporting System (NORS) began collecting supply chain contamination data as part of foodborne outbreak (FBO) traceback investigations. We created an integrated FBO severity score measure and examined differences in FBO severity by geographic and supply chain contamination locations. We used 9,407 NORS records between 2009–2019 to demonstrate the utility of the proposed methodology.MethodsThe severity scores were composed of 11 metrics based on outbreak intensity and duration characteristics and metrics’ completeness. Metrics were normalized (with natural log-transformation), calibrated (to 0–1 scale), and weighed (by completeness) across all recorded outbreaks. Individual outbreak scores ranged from 0 (lowest severity) to 1 (highest severity). We compared averages of severity scores across geographic (i.e., multistate and single state exposure outbreak) and supply chain contamination locations (i.e., suspected or confirmed before preparation, preparation, unknown and missing) using tobit-regression models.ResultsAll FBOs reported the state of exposure; 5,500 (58.5%) reported supply chain contamination location. Multistate exposure FBOs had higher median severity scores than single state outbreaks (0.54 [0.44, 0.67] vs 0.28 [0.16, 0.41], P < 0.001). FBOs with reported point of contamination that occurred before preparation had higher median severity scores than all other stages (0.36 [0.27, 0.49] vs 0.26 [0.15, 0.41], 0.25 [0.13, 0.39], and 0.29 [0.16, 0.43], P < 0.001, for preparation, unknown and missing stages respectively).ConclusionsUnderstanding an FBO's severity by geographic and supply chain contamination location helps to quantify supply chain vulnerability and improve monitoring of food safety. Identification of supply chain contamination at high level granularity and completeness is critical for developing foodborne outbreak (FBO) prediction analytics aimed to reduce both the volume and severity of outbreaks and illnesses.Funding SourcesDoD, ODNI, NIFA, NSF, USIAD.

Defoliation-Induced Growth Reduction of Pinus sylvestris L. after a Prolonged Outbreak of Diprion pini L.—A Case Study from Eastern Finland

The frequency and intensity of insect outbreaks have increased in boreal forests, along with associated impacts on the growth and economic losses of host trees. In Finland, the common pine sawfly (Diprion pini L.) is a serious pest, causing declines in health and growth responses of Scots pine (Pinus sylvestris L.). We focused on investigating the species’ defoliating impact on tree radial and volume growth and estimated the economic value of the declined growth. Managed P. sylvestris forests in our study area in eastern Finland have suffered from extended defoliation by D. pini for 15 years since 1999 at varying intensity levels. We classified 184 trees into four defoliation classes and compared annual growth, expressed as growth indices between the classes. We modelled tree volume, estimated economic loss, and compared those to a reference period preceding the initial outbreak. We found significant differences in growth indices between the defoliation classes. Growth losses of 4.2%, 20.8%, and 40.4% were obtained for the mild, moderate, and high defoliation classes, with related economic impacts of 51 €, 272 €, and 734 € per ha for 11 years, respectively. Growth was slightly enhanced in the lowest defoliation class. We suggest that growth-related economic loss caused by D. pini may be significant and depend on defoliation intensity and outbreak duration.

Risk factors associated with SARS-CoV-2 transmission, outbreak duration, and mortality in Fraser Health acute-care settings

Background: Transmission of SARS-CoV-2 in acute-care settings affects patients, healthcare workers, and the already-burdened healthcare system. An analysis of risk factors associated with outbreak severity was conducted to inform prevention strategies. Methods: This study was a cross-sectional analysis of COVID-19 outbreaks at Fraser Health (FH) acute-care sites between March 2020 and March 2021. Outbreak severity measures included COVID-19 attack rate, outbreak duration, and 30-day case mortality. Covariates at patient, outbreak, unit level, and facility level were included (Table 1). Generalized linear models with generalized estimation equations were used for all outcome measures, with outbreak duration and 30-day case mortality using multivariate negative binomial distributions, and attack rate using Gaussian distribution. A P value of .05 indicated statistical significance. Analyseswere performed using SAS version 3.8 software, R version 4.1.0 software, and Stata version 16.0 software. Results: Between March 2020 and March 2021, 54 COVID-19 outbreaks were declared in FH acute-care sites involving 455 SARS-CoV-2–positive patients. The average outbreak duration was 23 days, the average attack rate was 28%, and the average 30-day all-cause mortality per outbreak was 2 deaths. The results of the full models are shown in Table 1. Discussion: We identified an inverse relationship between increased hand hygiene compliance during outbreaks and all 3 severity measures. Paradoxically, hand hygiene rates in the year prior to the pandemic were positively associated with duration and mortality. Increased unit age was also associated with increases in each of the severity measures. Comorbidity total factor was correlated with outbreak attack rate and duration, demonstrating the importance of individual patient characteristics in an outbreak. Conclusions: Our findings highlight the importance of hand hygiene practices during an outbreak. Additionally, it is important to understand the difficulties faced by older facilities, many of which face infrastructural challenges. This study reinforces the need to incorporate infection control standards into healthcare planning and construction.Funding: NoneDisclosures: None

Outbreaks of Gastroenteritis Due to Norovirus in Schools and Summer Camps in Catalonia, 2017-2019.

ABSTRACTWe studied outbreaks of acute gastroenteritis due to norovirus in schools and summer camps during 2017–2019 in Catalonia (Spain). The overall attack rate was 21.27% in schools and 33.42% in summer camps (RR 0.64 [95% CI 0.58–0.70]) and 52.63% of outbreaks occurred in cold months and 47.37% in warm months. The mean delay in reporting was 5.61 days (SD 5.58 days) and the mean duration was 6.11 days (SD 6.08 days), with a Pearson correlation coefficient of 0.84 (P < 0.001) between these variables. In outbreaks with person-to-person transmission, the aOR was higher the longer the delay in reporting: 3.07 (95% CI 1.21–7.81) when the delay was 5–8 days and 3.81 when it was >9 days (95% CI 1.42–10.23). The cold months posed a higher risk than the warm months. In common source outbreaks the risk was higher in children in secondary-higher education and in summer camps.IMPORTANCE Norovirus is the main cause of viral acute gastroenteritis outbreaks worldwide. The low infectious dose and the lack of long-term immunity in infected persons means that norovirus often causes outbreaks in institutions and closed and semiclosed centers. Norovirus gastroenteritis are usually mild, with no complications, but occasionally can result in hospital admission. Understanding the risk factors involved in a norovirus outbreak can reduce the spread, severity, and duration of the outbreak and, when a vaccine becomes available, this understanding would help us identify the population groups need to get vaccinated. Here, we show the outbreaks due to norovirus in schools and summer camps, the correlation between the delay in reporting and duration of outbreaks and the relationship of the attack rate and the size of the groups.

Invasive Group A Streptococcus Outbreaks Associated with Home Healthcare, England, 2018-2019.

Healthcare-associated invasive group A Streptococcus (iGAS) outbreaks are common worldwide, but only England has reported outbreaks associated with home healthcare (HHC). We describe 10 outbreaks during 2018-2019 in England. A total of 96 iGAS cases (range 2-39 per outbreak) and 28 deaths (case-fatality rate 29%) occurred. Outbreak duration ranged from 3-517 days; median time between sequential cases was 20.5 days (range 1-225 days). Outbreak identification was difficult, but emm typing and whole-genome sequencing improved detection. Network analyses indicated multiple potential transmission routes. Screening of 366 HHC workers from 9 outbreaks identified group A Streptococcus carriage in just 1 worker. Outbreak control required multiple interventions, including improved infection control, equipment decontamination, and antimicrobial prophylaxis for staff. Transmission routes and effective interventions are not yet clear, and iGAS outbreaks likely are underrecognized. To improve patient safety and reduce deaths, public health agencies should be aware of HHC-associated iGAS.

Epidemiological characteristics of varicella outbreaks in the Republic of Korea, 2016-2020.

ObjectivesWe described the trends and epidemiological characteristics of varicella outbreaks from 2016 to 2020 in the Republic of Korea.Methods We investigated variables such as the outbreak setting, age of patients, vaccination status, and lesion count. The collected data were analyzed with the Cochrane-Armitage trend test and Kruskal-Wallis test. These statistical tests were performed using R ver. 4.0.3.ResultsThe number of varicella outbreaks increased from 2016 to 2018; however, after a slight decrease in the number of outbreaks in 2019, the number fell sharply in 2020. The median size of outbreaks decreased from 8 to 9 cases during 2016−2019 to 6 cases in 2020. The median duration of outbreaks was 18 days during 2016−2017, 28 days in 2018, 29 days in 2019, and 15 days in 2020. Varicella outbreaks occurred most frequently in elementary schools, and vaccination coverage of patients increased from 89.4% in 2016 to 97.2% in 2019. The median age of patients with outbreak-related varicella decreased from 8 years in 2016 to 6 years in 2020.ConclusionSignificant changes were observed in the age of patients with outbreak-related varicella. Ongoing monitoring of varicella outbreaks should be conducted. Further research will be needed to measure the disease burden of varicella and enable evidence-based policy decisions.

Epidemiology of Indigenous Dengue Cases in Zhejiang Province, Southeast China.

ObjectiveAutochthonous transmission of the dengue virus (DENV) occurred each year from 2014 to 2018 in Zhejiang province, and became an emerging public health problem. We characterized the autochthonous transmission of the DENV and traced the source of infection for further control and prevention of dengue.MethodsDescriptive and spatiotemporal cluster analyses were conducted to characterize the epidemiology of autochthonous transmission of the DENV. Molecular epidemiology was used to identify the infection source.ResultsIn total, 1,654 indigenous cases and 12 outbreaks, with no deaths, were reported during 2004–2018. Before 2017, all outbreaks occurred in suburban areas. During 2017–2018, five out of eight outbreaks occurred in urban areas. The median duration of outbreaks (28 days) in 2017–2018 was shortened significantly (P = 0.028) in comparison with that in 2004–2016 (71 days). The median onset-visiting time, visiting-confirmation time, and onset-confirmation time was 1, 3, and 4 days, respectively. The DENV serotypes responsible for autochthonous transmission in Zhejiang Province were DENV 1, DENV 2, and DENV 3, with DENV 1 being the most frequently reported. Southeast Asia was the predominant source of indigenous infection.ConclusionsZhejiang Province witnessed an increase in the frequency, incidence, and geographic expansion of indigenous Dengue cases in recent years. The more developed coastal and central region of Zhejiang Province was impacted the most.

The use of core genome multilocus sequence typing to determine the duration of vancomycin-resistant Enterococcus faecium outbreaks.

The prevalence of vancomycin-resistant Enterococcus faecium has increased rapidly, and in Denmark, we are facing an endemic outbreak situation in hospitals. The aim of this study was to use whole-genome sequencing (WGS) and core genome multilocus sequencing typing (cgMLST) to determine the duration of VREfm outbreaks and thereby evaluate the effect of our infection control strategies. We included all VREfm isolates from six hospitals in the Capital Region of Denmark that were sequenced between 2012 and 2020. Ward data were collected from our laboratory information system. A ward outbreak was defined as two patient samples from the same ward within a period of 30 days belonging to the same cgMLST cluster. cgMLST complex types were determined using Ridom SeqSphere v7.2.3, where a maximum of 20 allelic differences between isolates defines a cluster. We included 1690 patient isolates between 2012 and 2020. Our collection consisted of 45 unique clusters and 227 ward outbreaks. The median duration of outbreaks was 20 days. We reported a median outbreak duration of VREfm outbreaks based on WGS data to be 20 days, and thus concluded that our infection control precautions are adequate.

Healthcare-associated COVID-19 outbreaks: a nationwide population-based cohort study

BackgroundHealthcare-associated coronavirus disease 2019 (COVID-19) has significant implications for patients, their companions and healthcare workers (HCWs). Controlling transmission in healthcare settings is critical to reduce deaths due to COVID-19.AimTo describe the epidemiology and characteristics of healthcare-associated COVID-19 outbreaks and outbreak-related cases.MethodsThe investigation data for each healthcare-associated outbreak that occurred between 15th January 2020 and 31st July 2021 in Taiwan were analysed retrospectively. Confirmed outbreak-associated cases were categorized as HCW cases, patient companion cases or patient cases, and the characteristics of the confirmed cases were compared between these categories.FindingsIn total, 54 healthcare-associated COVID-19 outbreaks including 512 confirmed cases were reported. The median number of affected cases per outbreak was six [interquartile range (IQR) 2–12], and the median outbreak duration was 12 days (IQR 4.3–17.0). Only 5.7% and 0.2% of all confirmed cases were partially and fully vaccinated, respectively. Most outbreaks (90%, 48/54) occurred in May and June 2021. HCW cases, companion cases and patient cases accounted for 19.5%, 41.2% and 39.3% of the total cases. Patient cases were significantly older (median age 72 years, IQR 61–83) and had higher 30-day all-cause mortality (37.4%) than HCW cases (median age 41 years, IQR 28–58, 0%) and companion cases (median age 52 years; IQR 42–62, 1%).ConclusionHealthcare-associated COVID-19 outbreaks have a critical impact on patients. Nevertheless, two-thirds of cases in the healthcare-associated outbreaks in this study comprised HCWs and companions. In order to effectively mitigate COVID-19 transmission in healthcare settings, multi-pronged infection prevention and control measures should be implemented and tailored for these three groups.

Multi-disciplinary Leadership to Mitigate COVID-19 in an Austere West African Military Environment.

The COVID-19 pandemic created challenges for forward-deployed military units to Western Africa. Austere military environments afford multiple avenues to transmit COVID-19 amongst service members. A COVID-19 outbreak on a military base in Western Africa spanning over 100 days is statistically analyzed using a Pearson's correlation coefficient. Furthermore, a COVID-19 reproductive number (R0) is evaluated to examine the relationship between specific command-directed policies to mitigate COVID-19 transmission. The multidisciplinary partnership of military command, medical, and public health leadership implemented evidence-based and epidemiologically informed COVID-19 preventive base-wide policies, including appropriate isolation/quarantine policies. The R0 for the outbreak was 0.03 and remained <1 for the outbreak duration. This base remained COVID-19 free for multiple weeks after policy implementation. The implementation of practical mitigating base-wide policies through seamless communication between military command/medical/public health leadership resolved the COVID-19 outbreak while maintaining mission readiness. Weekly COVID-19 testing epidemiological data may be utilized by commanders to direct further decision-making on tightening/loosening base-wide policy restrictions for continued mission-essential operations, e.g., security, food service, or airfield operations.

Evaluating Completeness of Foodborne Outbreak Reporting in the United States, 1998-2019.

Public health agencies routinely collect time-referenced records to describe and compare foodborne outbreak characteristics. Few studies provide comprehensive metadata to inform researchers of data limitations prior to conducting statistical modeling. We described the completeness of 103 variables for 22,792 outbreaks publicly reported by the United States Centers for Disease Control and Prevention’s (US CDC’s) electronic Foodborne Outbreak Reporting System (eFORS) and National Outbreak Reporting System (NORS). We compared monthly trends of completeness during eFORS (1998–2008) and NORS (2009–2019) reporting periods using segmented time series analyses adjusted for seasonality. We quantified the overall, annual, and monthly completeness as the percentage of outbreaks with blank records per our study period, calendar year, and study month, respectively. We found that outbreaks of unknown genus (n = 7401), Norovirus (n = 6414), Salmonella (n = 2872), Clostridium (n = 944), and multiple genera (n = 779) accounted for 80.77% of all outbreaks. However, crude completeness ranged from 46.06% to 60.19% across the 103 variables assessed. Variables with the lowest crude completeness (ranging 3.32–6.98%) included pathogen, specimen etiological testing, and secondary transmission traceback information. Variables with low (<35%) average monthly completeness during eFORS increased by 0.33–0.40%/month after transitioning to NORS, most likely due to the expansion of surveillance capacity and coverage within the new reporting system. Examining completeness metrics in outbreak surveillance systems provides essential information on the availability of data for public reuse. These metadata offer important insights for public health statisticians and modelers to precisely monitor and track the geographic spread, event duration, and illness intensity of foodborne outbreaks.

Analysing foodborne illness outbreak severity in the USA, 2009–19

BackgroundIn the USA, one in six Americans have had a foodborne illness, resulting in approximately US$17·6 billion (2018) of losses annually attributed to medical costs, productivity losses, and economic burden due to death. Previous research has characterised these burdens with use of various methods, including disability-adjusted life-years (DALYs), medical care costs, and revenue losses of food retailers. However, these indices assess only the socioeconomic burdens of outbreaks without providing an index to compare the health-related severity of outbreaks regarding geographical spread of transmission, outbreak duration, and the morbidity and mortality of case outcomes. MethodsIn this study, we proposed a data-driven index for evaluating outbreak severity using the publicly available US Centers for Disease Control and Prevention's National Outbreak Reporting System (NORS) database from Jan 1, 2009, to Dec 31, 2019. We identified 67 metrics related to the geographical extent (eg, counties or states where individuals with a foodborne illness resided and were exposed), case severity (eg, primary cases, hospital admissions, emergency room visits, and deaths), duration (eg, days of illness and days of exposure events), and their ratios. We selected 11 metrics to create the index on the basis of completeness and distributional characteristics of these metrics. We generated index scores by normalising natural log-transformed values on a 0–1 scale and averaging all metrics per outbreak. Scores ranged from 0 (lowest severity) to 1 (highest severity). FindingsNORS reported 9407 outbreaks in our 11-year study period. We found that bacterial outbreaks associated with the genera Streptococcus, Listeria, and Salmonella had the highest median severity scores, whereas Bacillus, Staphylococcus, and Clostridium had the lowest scores. Among protozoa, Cryptosporidium and Cyclospora had the lowest median scores, whereas Giardia and Toxoplasma had the highest scores. Hepatitis had the highest median score for virus-associated outbreaks, whereas Norovirus, which had the most outbreaks reported in our study period (n=3088), had the lowest score. InterpretationOur index illustrates the usefulness of publicly reported surveillance data in establishing a data-driven approach for monitoring the severity of foodborne outbreaks regarding their spread, duration, and morbidity and mortality. Differences in outbreak severity by pathogen inform how to best allocate resources for monitoring, tracking, and preventing foodborne disease outbreaks. Being data driven, our index emphasises the importance of improved data quality, integrity, and completeness of surveillance records. Future research should strive to validate this index by use of longitudinal cohort studies. FundingUS Department of Defense, National Institute of Food and Agriculture.

Epidemiological and Genetic Characterization of Norovirus Outbreaks That Occurred in Catalonia, Spain, 2017-2019.

Molecular characterization of human norovirus (HuNoV) genotypes enhances the understanding of viral features and illustrates distinctive evolutionary patterns. The aim of our study was to describe the prevalence of the genetic diversity and the epidemiology of the genotypes involved in HuNoV outbreaks in Catalonia (Spain) between 2017 and 2019. A total of 100 HuNoV outbreaks were notified with the predominance of GII (70%), followed by GI (27%) and mixed GI/GII (3%). Seasonality was observed for GII outbreaks only. The most prevalent genotypes identified were GII.4[P31] Sydney 2012, GII.4[P16] Sydney 2012 and GII.2[P16]. As compared to person-to-person (P/P) transmitted outbreaks, foodborne outbreaks showed significantly higher attack rates and lower duration. The average attack rate was higher in youth hostel/campgrounds compared to nursing homes. Only genotypes GI.4[P4], GII.2[P16], GII.4[P16], GII.4[P31] and GII.17[P17] were consistently detected every year, and only abundance of GII.2[P16] showed a negative trend over time. GII.4 Sydney 2012 outbreaks were significantly associated to nursing homes, while GII.2[P16] and GI.3[P3] were most frequently identified in youth hostel/campgrounds. The average attack rate was significantly higher when comparing GII.2[P16] vs. GI.4[P4], GII.2[P16] vs. GII.4[P31] Sydney 2012, and GII.6[P7] vs. GII.4[P31] Sydney 2012. No correlations were found between genotype and outbreak duration or age of affected individuals.

Modeling anticipated changes in numbers of SARS-CoV-2 infections within communities due to immunization campaigns

Background: As SARS-CoV-2 spread in early 2020, uncertainty about the scope, duration, and impact of the unfolding outbreaks caused numerous countries to interrupt many routine activities, including health services. Because immunization is an essential health service, modeling changes in SARS-CoV-2 infections among communities and health workers due to different vaccination activities was undertaken to understand the risks and to inform approaches to resume services. Methods: Agent-based modeling examined the impact of Supplemental Immunization Activities (SIAs) delivery strategies on SARS-CoV-2 transmission in communities and health workers for six countries capturingvarious demographic profiles and health system performance: Angola, Ecuador, Lao PDR, Nepal, Pakistan, and Ukraine. Results: Urban, fixed-post SIAs during periods of high SARS-CoV-2 prevalence increased infections within the community by around 28 [range:0-79] per 1000 vaccinations. House-to-house SIAs in mixed urban and rural contexts may import infections into previously naïve communities. Infections are elevated by around 60 [range:0-230] per 1000 vaccinations, but outcomes are sensitive to prevalence in health workers and SIA timing relative to peak. Conclusions: Younger populations experience lower transmission intensity and fewer excess infections per childhood vaccine delivered. Large rural populations have lower transmission intensity but face a greater risk of introduction of SARS-CoV-2 during an SIA.

Economic benefits of implementing trading zones for Australian livestock disease outbreaks of limited duration.

ObjectiveThe objective is to estimate the economic benefits of trading zones as part of foot‐and‐mouth disease (FMD) control measures for limited duration outbreaks.DesignThe proposed trading zones for FMD at the state level are determined using multiple tools. Eleven individual incursion scenarios in six Australian states are simulated within the Australian Animal Disease Spread epidemiological model to identify the potential geographic extent of outbreaks, as well as the number of animals infected and the duration of outbreaks. The disease spread information is used to identify the boundaries of trading zones. The outbreak duration data are combined with historical export data to estimate the share of Australian exports that could be embargoed. The market impacts of the potential export embargoes including changes in equilibrium quantities, prices and revenue are simulated within the Australian Bureau of Agricultural and Resource Economics and Sciences' AgEmissions partial equilibrium model of Australian agriculture.ResultsResults emphasize the importance of jurisdictional and outbreak characteristics in determining trading zones. Should Australia effectively implement trading zones at the state level in response to small FMD outbreaks, the potential reductions of embargoed exports lead to a reduction in estimated producer revenue losses compared with losses under a national embargo. Producer revenue losses are reduced between $3 billion and $9 billion estimated in present value terms over 10 years at a 7% discount rate.ConclusionEconomic analysis of the implications of trading zones identifies additional investments that would be of value to livestock industries.

Modeling the early transmission of COVID-19 in New York and San Francisco using a pairwise network model.

Classical epidemiological models assume mass action. However, this assumption is violated when interactions are not random. With the recent COVID-19 pandemic, and resulting shelter in place social distancing directives, mass action models must be modified to account for limited social interactions. In this paper we apply a pairwise network model with moment closure to study the early transmission of COVID-19 in New York and San Francisco and to investigate the factors determining the severity and duration of outbreak in these two cities. In particular, we consider the role of population density, transmission rates and social distancing on the disease dynamics and outcomes. Sensitivity analysis shows that there is a strongly negative correlation between the clustering coefficient in the pairwise model and the basic reproduction number and the effective reproduction number. The shelter in place policy makes the clustering coefficient increase thereby reducing the basic reproduction number and the effective reproduction number. By switching population densities in New York and San Francisco we demonstrate how the outbreak would progress if New York had the same density as San Francisco and vice-versa. The results underscore the crucial role that population density has in the epidemic outcomes. We also show that under the assumption of no further changes in policy or transmission dynamics not lifting the shelter in place policy would have little effect on final outbreak size in New York, but would reduce the final size in San Francisco by 97%.

Investigating the association between COVID-19 vaccination and care home outbreak frequency and duration

ObjectivesAt the end of 2020, many countries commenced a vaccination programme against SARS-CoV-2. Public health authorities aim to prevent and interrupt outbreaks of infectious disease in social care settings. We aimed to investigate the association between the introduction of the vaccination programme and the frequency and duration of COVID-19 outbreaks in Northern Ireland (NI). Study designWe undertook an ecological study using routinely available national data. MethodsWe used Poisson regression to measure the relationship between the number of RT-PCR confirmed COVID-19 outbreaks in care homes, and as a measure of community COVID-19 prevalence, the Office for National Statistics COVID-19 Infection Survey estimated the number of people testing positive for COVID-19 in NI. We estimated the change in this relationship and estimated the expected number of care home outbreaks in the absence of the vaccination programme. A Cox proportional hazards model estimated the hazard ratio of a confirmed COVID-19 care home outbreak closure. ResultsCare home outbreaks reduced by two-thirds compared to expected following the introduction of the vaccination programme, from a projected 1625 COVID-19 outbreaks (95% prediction interval 1553–1694) between 7 December 2020 and 28 October 2021 to an observed 501. We estimated an adjusted hazard ratio of 2.53 of the outbreak closure assuming a 21-day lag for immunity. ConclusionsThese findings describe the association of the vaccination with a reduction in outbreak frequency and duration across NI care homes. This indicates probable reduced harm and disruption from COVID-19 in social care settings following vaccination. Future research using individual level data from care home residents will be needed to investigate the effectiveness of the vaccines and the duration of their effects.

MODELING THE IMPACT OF EDUCATIONAL CAMPAIGN ON THE TRANSMISSION DYNAMICS OF EBOLA

Disease awareness that informs the public about the severity and transmission pathways of infectious diseases such as Ebola is key to curtailing an outbreak. Public health education when available can limit the intensity and duration of an Ebola outbreak in any community if there is compliance. It is important that all population groups be informed about the methods in which Ebola is transmitted to control the disease when there is an outbreak. In this paper, we study the impact of public health education that leads to behavioral changes on the dynamics of Ebola spread. The model is formulated as a system of ordinary differential equations and incorporates direct transmission from infectious, hospitalized, and deceased individuals with Ebola. We establish the existence of a disease free equilibrium and an endemic equilibrium, and investigate them for local and global stability. Model predictions show that a more informed community results in fewer cases, and thus limits the impact of an Ebola outbreak. Further, the model also predicts subsequent outbreak waves within a community in the absence of complete eradication. Lastly, the model successfully captures the dynamics of the 2014–2016 West Africa Ebola outbreak and the 2018–2020 Democratic Republic of Congo Ebola outbreak.