On modelling airborne infection risk.

Airborne infection risk analysis is usually performed for enclosed spaces where susceptible individuals are exposed to infectious airborne respiratory droplets by inhalation. It is usually based on exponential, dose-response models of which a widely used variant is the Wells-Riley (WR) model. We revisit this infection-risk estimate and extend it to the population level. We use an epidemiological model where the mode of pathogen transmission, airborne or contact, is explicitly considered. We illustrate the link between epidemiological models and the WR and the Gammaitoni and Nucci models. We argue that airborne infection quanta are, up to an overall density, airborne infectious respiratory droplets modified by a parameter that depends on biological properties of the pathogen, physical properties of the droplet and behavioural properties of the individual. We calculate the time-dependent risk of being infected for two scenarios. We show how the epidemic infection risk depends on the viral latent period and the event time, the time infection occurs. Infection risk follows the dynamics of the infected population. As the latent period decreases, infection risk increases. The longer a susceptible is present in the epidemic, the higher its risk of infection for equal exposure time to the pathogen is.

Glucose Tolerance and the Risk Factors for Transmission in Japanese SARS-CoV-2/WA-1/2020 Epicenter: A Retrospective Study.

Purpose: The severe pathogenic ancient-type COVID-19, SARS-CoV-2/WA-1/2020 was the predominant gene variant in early 2020 in Japan, however, its transmissibility was uncertain. The period before the public commenced using any personal protective equipment (PPE) was evaluating to describe the transmissibility of the SARS-CoV-2/WA-1/2020. We analyzed the secondary attack rate (SAR) among close contacts and the risk factor for SAR. Methods: This retrospective cohort study included a total of 539 patients who were anticipated for the SARS-CoV-2/WA-1/2020 infection at Toho University Medical Center Omori Hospital from February to May 2020. We selected 54 patients with 1) exclude other pathogens infection, 2) include "Three Cs" condition: crowded places between distance< 6 feet, closed spaces indoor and close contact settings involving contact >15min with a person tested positive for SARS-CoV-2/WA-1/2020 without PPE. We evaluated alternative infection risks: the body mass index (BMI) and diabetes (DM) status (non-DM, pre-DM, and DM) as demographic determinants of transmissibility and infectivity of SARS-CoV2/WA-1/2020 cases during the incubation period. Results: The calculated SAR was 79.3%. BMI was significantly associated with the PCR positivity rate, which was significant in the univariate (CI 95%, 1.02-1.51; P = 0.03) and multivariate (CI 95%, 1.02-1.60; P = 0.03) analyses. Comparing the different BMI groups, the highest BMI group (25.5-35.8 kg/m2) had an elevated risk of SAR compared to the lowest BMI group (14.0-22.8 kg/m2), with an odds ratio of 1.41 (95% CI, 1.02-1.59; P = 0.03). There were no significant differences in the risk of SAR among different DM statuses. Conclusion: The transmissibility of SARS-CoV2/WA-1/2020 was high (79.3%) among household members without PPE who had "Three Cs" exposure. Although pre-DM and established DM did not confer a risk for transmissibility, higher BMI was associated with an increased risk of SAR. Trial Registration: UMIN Clinical Trials Registry, UMIN0000 50905.

The Risk of Aircraft-Acquired SARS-CoV-2 Transmission during Commercial Flights: A Systematic Review.

The aircraft-acquired transmission of SARS-CoV-2 poses a public health risk. Following PRISMA guidelines, we conducted a systematic review and analysis of articles, published prior to vaccines being available, from 24 January 2020 to 20 April 2021 to identify factors important for transmission. Articles were included if they mentioned index cases and identifiable flight duration, and excluded if they discussed non-commercial aircraft, airflow or transmission models, cases without flight data, or that were unable to determine in-flight transmission. From the 15 articles selected for in-depth review, 50 total flights were analyzed by flight duration both as a categorical variable-short (<3 h), medium (3-6 h), or long flights (>6 h)-and as a continuous variable with case counts modeled by negative binomial regression. Compared to short flights without masking, medium and long flights without masking were associated with 4.66-fold increase (95% CI: [1.01, 21.52]; p < 0.0001) and 25.93-fold increase in incidence rates (95% CI: [4.1, 164]; p < 0.0001), respectively; long flights with enforced masking had no transmission reported. A 1 h increase in flight duration was associated with 1.53-fold (95% CI: [1.19, 1.66]; p < 0.001) increase in the incidence rate ratio (IRR) of cases. Masking should be considered for long flights.

Monitoring and assessment of CO2 and NO2 in schools within the Sentinel Schools Network of Catalonia during the COVID-19 era.

In response to the global impact of the COVID-19 pandemic, international and national authorities, including those in Catalonia (Spain), recognized the crucial need to ensure proper ventilation in classrooms, emphasizing the importance of safe and healthy indoor environments for face-to-face learning. The present work, conducted within the COVID-19 Sentinel Schools Network of Catalonia (CSSNC) framework, aimed to monitor carbon dioxide (CO2) and nitrogen dioxide (NO2) concentrations in 23 schools, ensuring a comprehensive sample regarding educational levels, daily scholar schedules, and classroom typologies distributed across the four provinces of Catalonia. The research spanned three study periods: March and April 2021, October 2021 to January 2022, and March to June 2022. Briefly, 28%, 25%, and 37% of classrooms surpassed the 700 parts per million (ppm) CO2 limit in each study period, respectively. Generally, CO2 averages were lower in preschool classrooms (mean ± SD = 486 ± 106 ppm), while high school classrooms displayed the highest CO2 concentrations (mean ± SD = 710 ± 253 ppm). Moreover, classrooms in towns (<30000 inhabitants) exhibited higher CO2 levels as compared to classrooms from schools located in cities. As for NO2, the highest averages were obtained in urban areas, particularly in the Barcelona metropolitan area (e.g. mean indoor levels of 24.56 µg m-3 as compared to 11.05 µg m-3 in towns). In addition, the Indoor/Outdoor ratio (I/O ratio) in towns was the lowest (0.60). These results, together with the higher concentration of CO2 indoors, could indicate poorer ventilation in town schools. The results of this study are anticipated to contribute to implementing evidence-based measures to improve indoor air quality (IAQ) in educational settings.

A model for SARS-CoV-2 virus transmission on the upper deck of a passenger ship bound for a short trip.

Public transportation plays a critical role in meeting transportation demands, particularly in densely populated areas. The COVID-19 pandemic has highlighted the importance of public health measures, including the need to prevent the spread of the virus through public transport. The spreading of the virus on a passenger ship is studied using the Computational Fluid Dynamic (CFD) model and Monte Carlo simulation. A particular focus was the context of Bangladesh, a populous maritime nation in South Asia, where a significant proportion of the population utilizes passenger ships to meet transportation demands. In this regard, a turbulence model is used, which simulates the airflow pattern and determines the contamination zone. Parameters under investigation are voyage duration, number of passengers on board, social distance, the effect of surgical masks, and others. This study shows that the transmission rate of SARS-CoV-2 infection on public transport, such as passenger ships, is not necessarily directly proportional to voyage duration or the number of passengers onboard. This model has the potential to be applied in various other modes of transportation, including public buses and airplanes. Implementing this model may help to monitor and address potential health risks effectively in the public transport networks.

Public Health Impact of Paxlovid as Treatment for COVID-19, United States.

We evaluated the population-level benefits of expanding treatment with the antiviral drug Paxlovid (nirmatrelvir/ritonavir) in the United States for SARS-CoV-2 Omicron variant infections. Using a multiscale mathematical model, we found that treating 20% of symptomatic case-patients with Paxlovid over a period of 300 days beginning in January 2022 resulted in life and cost savings. In a low-transmission scenario (effective reproduction number of 1.2), this approach could avert 0.28 million (95% CI 0.03-0.59 million) hospitalizations and save US $56.95 billion (95% CI US $2.62-$122.63 billion). In a higher transmission scenario (effective reproduction number of 3), the benefits increase, potentially preventing 0.85 million (95% CI 0.36-1.38 million) hospitalizations and saving US $170.17 billion (95% CI US $60.49-$286.14 billion). Our findings suggest that timely and widespread use of Paxlovid could be an effective and economical approach to mitigate the effects of COVID-19.

COVID-19 risk mitigation in reopening mass cultural events: population-based observational study for the UK Events Research Programme in Liverpool City Region.

OBJECTIVES: To understand severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission risks, perceived risks and the feasibility of risk mitigations from experimental mass cultural events before coronavirus disease 2019 (COVID-19) restrictions were lifted. DESIGN: Prospective, population-wide observational study. SETTING: Four events (two nightclubs, an outdoor music festival and a business conference) open to Liverpool City Region UK residents, requiring a negative lateral flow test (LFT) within the 36 h before the event, but not requiring social distancing or face-coverings. PARTICIPANTS: A total of 12,256 individuals attending one or more events between 28 April and 2 May 2021. MAIN OUTCOME MEASURES: SARS-CoV-2 infections detected using audience self-swabbed (5-7 days post-event) polymerase chain reaction (PCR) tests, with viral genomic analysis of cases, plus linked National Health Service COVID-19 testing data. Audience experiences were gathered via questionnaires, focus groups and social media. Indoor CO2 concentrations were monitored. RESULTS: A total of 12 PCR-positive cases (likely 4 index, 8 primary or secondary), 10 from the nightclubs. Two further cases had positive LFTs but no PCR. A total of 11,896 (97.1%) participants with scanned tickets were matched to a negative pre-event LFT: 4972 (40.6%) returned a PCR within a week. CO2 concentrations showed areas for improving ventilation at the nightclubs. Population infection rates were low, yet with a concurrent outbreak of >50 linked cases around a local swimming pool without equivalent risk mitigations. Audience anxiety was low and enjoyment high. CONCLUSIONS: We observed minor SARS-CoV-2 transmission and low perceived risks around events when prevalence was low and risk mitigations prominent. Partnership between audiences, event organisers and public health services, supported by information systems with real-time linked data, can improve health security for mass cultural events.

Predictors of Willingness to Participate in COVID-19 Screening Testing from a Pilot School Survey in the United States.

BACKGROUND: COVID-19 screening testing (ST) can detect asymptomatic or pre-symptomatic cases, allowing for prompt identification of cases and close contacts. This study examined parents' and school staffs' knowledge and attitudes toward to a pilot school-based ST program in a school district in southern Arizona. METHODS: In May 2021, online surveys to parents and school staff were administered to examine attitudes toward ST and impacts of the COVID-19 pandemic. Unweighted percent estimates were calculated, and bivariate differences were examined by demographics. Associations were assessed using chi-square tests and logistic regression. RESULTS: The survey had response rates of 10% (606/6085) and 22% (187/849) among parents and staff, respectively. Approximately one-third of responding parents (35%) would or already allow their child to participate in school-based ST, 37% would not participate; 28% were unsure. Among responding staff, 46% would or already participate in ST, 33% would not; 21% were unsure. The top concern (38%) among responding staff was taking job-related leave if testing positive. CONCLUSION: Schools work to balance the needs of students, families, and staff by implementing supportive and flexible policies and practices founded on buy-in and acceptance from their communities.

Impact of respiratory aerosol size and number distribution on the relative importance of different routes in SARS-CoV-2 transmission.

Exploring the relative importance of different routes in SARS-CoV-2 transmission is crucial in infection prevention. However, even in the same environmental setting, the relative importance of different routes has varied in different studies. We hypothesize that respiratory aerosol size and number distribution might play a key role. In this study, size and number distribution of respiratory droplets emitted from breathing, talking, and coughing were identified from PubMed and Web of Science. The infection risk of SARS-CoV-2 via airborne, droplet, and fomite transmission routes was modeled in a household and a healthcare setting. The relative importance of three routes varied with different size distributions in both settings. Generally, the contribution of the airborne route increased with the volume percentage of respirable droplets emitted. And the increase of the total number of emitted droplets leads to an increase in the contribution of tdroplet route. In the healthcare setting, as the total number of emitted droplets increased from 110 to 4,973, the contribution of droplet route increased from 62.24% to 98.11%. Next, by considering the combination of breathing, coughing, and talking when the infected person was asymptomatic, the airborne route predominated over the droplet and contact routes. When the infected person had developed symptoms, that is, cough, the droplet route played a dominant role in SARS-CoV-2 transmission. In conclusion, risk analyses will be improved with improved sampling methods that enable characterization of viruses within respiratory droplets of different sizes.

The public health impact of Paxlovid COVID-19 treatment in the United States.

The antiviral drug Paxlovid has been shown to rapidly reduce viral load. Coupled with vaccination, timely administration of safe and effective antivirals could provide a path towards managing COVID-19 without restrictive non-pharmaceutical measures. Here, we estimate the population-level impacts of expanding treatment with Paxlovid in the US using a multi-scale mathematical model of SARS-CoV-2 transmission that incorporates the within-host viral load dynamics of the Omicron variant. We find that, under a low transmission scenario Re∼1.2 treating 20% of symptomatic cases would be life and cost saving, leading to an estimated 0.26 (95% CrI: 0.03, 0.59) million hospitalizations averted, 30.61 (95% CrI: 1.69, 71.15) thousand deaths averted, and US$52.16 (95% CrI: 2.62, 122.63) billion reduction in health- and treatment-related costs. Rapid and broad use of the antiviral Paxlovid could substantially reduce COVID-19 morbidity and mortality, while averting socioeconomic hardship.

Potential transmission of SARS-CoV-2 through microplastics in sewage: A wastewater-based epidemiological review.

In light of the current COVID-19 pandemic caused by the virus SARS-CoV-2, there is an urgent need to identify and investigate the various pathways of transmission. In addition to contact and aerosol transmission of the virus, this review investigated the possibility of its transmission via microplastics found in sewage. Wastewater-based epidemiological studies on the virus have confirmed its presence and persistence in both influent sewage as well as treated ones. The hypothesis behind the study is that the huge amount of microplastics, especially Polyvinyl Chloride and Polyethylene particles released into the open waters from sewage can become a good substrate and vector for microbes, especially Polyvinyl Chloride and Polyethylene particles, imparting stability to microbes and aiding the "plastisphere" formation. A bibliometric analysis highlights the negligence of research toward plastispheres and their presence in sewage. The ubiquity of microplastics and their release along with the virus into the open waters increases the risk of viral plastispheres. These plastispheres may be ingested by aquatic organisms facilitating reverse zoonosis and the commercial organisms already reported with accumulating microplastics through the food chain poses a risk to human populations as well. Reliance of high population density areas on open waters served by untreated sewage in economically less developed countries might bring back viral transmission.

Analysis of metapopulation models of the transmission of SARS-CoV-2 in the United States.

During the COVID-19 pandemic, renewal equation estimates of time-varying effective reproduction numbers were useful to policymakers in evaluating the need for and impact of mitigation measures. Our objective here is to illustrate the utility of mechanistic expressions for the basic and effective (or intrinsic and realized) reproduction numbers, [Formula: see text] and related quantities derived from a Susceptible-Exposed-Infectious-Removed (SEIR) model including features of COVID-19 that might affect transmission of SARS-CoV-2, including asymptomatic, pre-symptomatic, and symptomatic infections, with which people may be hospitalized. Expressions from homogeneous host population models can be analyzed to determine the effort needed to reduce [Formula: see text] from [Formula: see text] to 1 and contributions of modeled mitigation measures. Our model is stratified by age, 0-4, 5-9, …, 75+ years, and location, the 50 states plus District of Columbia. Expressions from such heterogeneous host population models include subpopulation reproduction numbers, contributions from the above-mentioned infectious states, metapopulation numbers, subpopulation contributions, and equilibrium prevalence. While the population-immunity at which [Formula: see text] has captured the popular imagination, the metapopulation [Formula: see text] could be attained in an infinite number of ways even if only one intervention (e.g., vaccination) were capable of reducing [Formula: see text] However, gradients of expressions derived from heterogeneous host population models,[Formula: see text] can be evaluated to identify optimal allocations of limited resources among subpopulations. We illustrate the utility of such analytical results by simulating two hypothetical vaccination strategies, one uniform and other indicated by [Formula: see text] as well as the actual program estimated from one of the CDC's nationwide seroprevalence surveys conducted from mid-summer 2020 through the end of 2021.

Reconstruction of SARS-CoV-2 outbreaks in a primary school using epidemiological and genomic data.

Mathematical modelling studies have shown that repetitive screening can be used to mitigate SARS-CoV-2 transmission in primary schools while keeping schools open. However, not much is known about how transmission progresses within schools and whether there is a risk of importation to households. During the academic year 2020-2021, a prospective surveillance study using repetitive screening was conducted in a primary school and associated households in Liège (Belgium). SARS-CoV-2 screening was performed via throat washing either once or twice a week. We used genomic and epidemiological data to reconstruct the observed school outbreaks using two different models. The outbreaker2 model combines information on the generation time and contact patterns with a model of sequence evolution. For comparison we also used SCOTTI, a phylogenetic model based on the structured coalescent. In addition, we performed a simulation study to investigate how the accuracy of estimated positivity rates in a school depends on the proportion of a school that is sampled in a repetitive screening strategy. We found no difference in SARS-CoV-2 positivity between children and adults and children were not more often asymptomatic compared to adults. Both models for outbreak reconstruction revealed that transmission occurred mainly within the school environment. Uncertainty in outbreak reconstruction was lowest when including genomic as well as epidemiological data. We found that observed weekly positivity rates are a good approximation to the true weekly positivity rate, especially in children, even when only 25% of the school population is sampled. These results indicate that, in addition to reducing infections as shown in modelling studies, repetitive screening in school settings can lead to a better understanding of the extent of transmission in schools during a pandemic and importation risk at the community level.

Perinatal Transmission of SARS-CoV-2 Infection and Its Clinical Attributes: A Single-Center Study From Western Uttar Pradesh.

Background Globally, severe acute respiratory syndrome coronavirus 2 (SARS­CoV­2) has infected millions of people to date. The morbidity and mortality associated with SARS-CoV-2 are higher in diabetics than those with chronic kidney disease and in the elderly. In pregnant women, it causes an increased risk for preeclampsia/eclampsia, infections, intensive care unit (ICU) admission, maternal mortality, and preterm birth. In neonates, SARS­CoV­2 infection has been found to cause stillbirths, growth retardation, premature delivery, increased neonatal intensive care unit (NICU) admission, and need for oxygen support. The neonate can get infected by vertical or horizontal transmission. As most studies have focussed on transmission at the time of birth only, in this study, we explored both vertical and horizontal transmission along with the clinical attributes of those born to mothers with SARS­CoV­2 infection. Methodology A prospective observational study was conducted in the Department of Pediatrics of a tertiary care hospital over 12 months from October 2020 to October 2021. All reverse transcription-polymerase chain reaction (RT-PCR) SARS-CoV-2-positive pregnant females admitted to the facility during the study duration were included. The enrolled mothers were followed till delivery. The mothers and neonates were managed per standard guidelines. Delivery details and neonatal outcomes were recorded. Coronavirus disease 2019 sampling in newborn babies was done at birth (within 24 hours) using a nasopharyngeal swab sample for RTPCR along with cord blood for SARS-CoV-2 immunoglobulin M (IgM). Complete blood count, C-reactive protein, serum electrolytes, random blood sugar, and chest X-ray were obtained for all babies at birth and thereafter according to requirement. In those roomed in with their mother, RT-PCR was repeated at the time of discharge or if they became symptomatic. Results A total of 44 mother-neonate dyads were included in the study. Cord blood IgM for SARS­CoV­2 was negative for all neonates, while throat swab RT-PCR was positive for two (4.5%) neonates immediately after birth. Overall, 13.6% of the neonates were premature, 27.2% of the neonates had low birth weight (<2,500 g), and 6.8% had very low birth weight (<1,500 g). Among those admitted to the NICU, 18.2% had respiratory distress; 4.5% had fever, lethargy, and poor feeding; and hyperbilirubinemia requiring phototherapy was observed in 11.3% of the neonates. Moreover, 4.5% of the neonates had hypocalcemia on initial investigations. Mortality was seen in 2.2% (1/44) of the neonates. Rooming-in and breastfeeding were seen in 68.2% of the neonates. The horizontal transmission was seen in one (3.3%) roomed-in neonate. Conclusions Perinatal transmission of SARS­CoV­2 infection does occur but its rate is not significant. Furthermore, with proper infection prevention and control measures, the risk of perinatal transmission can be decreased. Breastfeeding and rooming-in do not increase infection transmission if the mother takes all precautions.

Social contact patterns during the COVID-19 pandemic in 21 European countries - evidence from a two-year study.

BACKGROUND: Most countries have enacted some restrictions to reduce social contacts to slow down disease transmission during the COVID-19 pandemic. For nearly two years, individuals likely also adopted new behaviours to avoid pathogen exposure based on personal circumstances. We aimed to understand the way in which different factors affect social contacts - a critical step to improving future pandemic responses. METHODS: The analysis was based on repeated cross-sectional contact survey data collected in a standardized international study from 21 European countries between March 2020 and March 2022. We calculated the mean daily contacts reported using a clustered bootstrap by country and by settings (at home, at work, or in other settings). Where data were available, contact rates during the study period were compared with rates recorded prior to the pandemic. We fitted censored individual-level generalized additive mixed models to examine the effects of various factors on the number of social contacts. RESULTS: The survey recorded 463,336 observations from 96,456 participants. In all countries where comparison data were available, contact rates over the previous two years were substantially lower than those seen prior to the pandemic (approximately from over 10 to < 5), predominantly due to fewer contacts outside the home. Government restrictions imposed immediate effect on contacts, and these effects lingered after the restrictions were lifted. Across countries, the relationships between national policy, individual perceptions, or personal circumstances determining contacts varied. CONCLUSIONS: Our study, coordinated at the regional level, provides important insights into the understanding of the factors associated with social contacts to support future infectious disease outbreak responses.

Analysis of serological surveys of antibodies to SARS-CoV-2 in the United States to estimate parameters needed for transmission modeling and to evaluate and improve the accuracy of predictions.

Seroprevalence studies can estimate proportions of the population that have been infected or vaccinated, including infections that were not reported because of the lack of symptoms or testing. Based on information from studies in the United States from mid-summer 2020 through the end of 2021, we describe proportions of the population with antibodies to SARS-CoV-2 as functions of age and time. Slices through these surfaces at arbitrary times provide initial and target conditions for simulation modeling. They also provide the information needed to calculate age-specific forces of infection, attack rates, and - together with contact rates - age-specific probabilities of infection on contact between susceptible and infectious people. We modified the familiar Susceptible-Exposed-Infectious-Removed (SEIR) model to include features of the biology of COVID-19 that might affect transmission of SARS-CoV-2 and stratified by age and location. We consulted the primary literature or subject matter experts for contact rates and other parameter values. Using time-varying Oxford COVID-19 Government Response Tracker assessments of US state and DC efforts to mitigate the pandemic and compliance with non-pharmaceutical interventions (NPIs) from a YouGov survey fielded in the US during 2020, we estimate that the efficacy of social-distancing when possible and mask-wearing otherwise at reducing susceptibility or infectiousness was 31% during the fall of 2020. Initialized from seroprevalence among people having commercial laboratory tests for purposes other than SARS-CoV-2 infection assessments on 7 September 2020, our age- and location-stratified SEIR population model reproduces seroprevalence among members of the same population on 25 December 2020 quite well. Introducing vaccination mid-December 2020, first of healthcare and other essential workers, followed by older adults, people who were otherwise immunocompromised, and then progressively younger people, our metapopulation model reproduces seroprevalence among blood donors on 4 April 2021 less well, but we believe that the discrepancy is due to vaccinations being under-reported or blood donors being disproportionately vaccinated, if not both. As experimenting with reliable transmission models is the best way to assess the indirect effects of mitigation measures, we determined the impact of vaccination, conditional on NPIs. Results indicate that, during this period, vaccination substantially reduced infections, hospitalizations and deaths. This manuscript was submitted as part of a theme issue on "Modelling COVID-19 and Preparedness for Future Pandemics."

Transmisión del SARS-CoV-2 en escolares durante el primer trimestre del curso 2021/2022 en la provincia de Albacete: incidencia e impacto de las nuevas variantes.

OBJECTIVE: The objective of this study was to know the evolution of the COVID-19 pandemic in the school setting, and the effect of the new variants on it. DESIGN: It is an observational longitudinal descriptive study during the first term of the academic year 21/22. SITE: Community health services. PARTICIPANTS: Preschool, elementary, secondary, and high school students. INTERVENTIONS: none. MAIN MEASUREMENTS: We calculated cumulative incidence stratified by grade, source of infection and follow-up period, percentage of vaccinated cases and correlation between cumulative incidence in schooled children per week and cumulative incidence in the general population. RESULTS: 1526 cases were reported, and the cumulative incidence was 3,17% and 0,48% in within-school acquired cases. 20,9% were vaccinated. During follow-up, there was an important change in incidence from weeks 49/21 on, at the time Omicron began to appear in Spain, with an increase in secondary cases, mostly high school students. We found a high correlation between general population and schooled children's cumulative incidence (R2 = 0,59). CONCLUSIONS: SARS-CoV-2 transmission in school settings has been affected by new circulating variants. Two propagation scenarios were identified, and they were like the community propagation pattern. This supports the hypothesis that school settings reflect the transmission in the community. Reinforcement of preventive measures and surveillance would have a positive effect on school settings.

COVID-19 host genetics and ABO blood group susceptibility.

Twenty-five susceptibility loci for SARS-CoV-2 infection and/or COVID-19 disease severity have been identified in the human genome by genome-wide association studies, and the most frequently replicated genetic findings for susceptibility are genetic variants at the ABO gene locus on chromosome 9q34.2, which is supported by the association between ABO blood group distribution and COVID-19. The ABO blood group effect appears to influence a variety of disease conditions and pathophysiological mechanisms associated with COVID-19. Transmission models for SARS-CoV-2 combined with observational public health and genome-wide data from patients and controls, as well as receptor binding experiments in cell lines and human samples, indicate that there may be a reduction or slowing of infection events by up to 60% in certain ABO blood group constellations of index and contact person in the early phase of a SARS-CoV-2 outbreak. The strength of the ABO blood group effect on reducing infection rates further depends on the distribution of the ABO blood groups in the respective population and the proportion of blood group O in that population. To understand in detail the effect of ABO blood groups on COVID-19, further studies are needed in relation to different demographic characteristics, but also in relation to recent data on reinfection with new viral variants and in the context of the human microbiome.

COVID-19 outbreak trends in Canada, 2021.

Background: In January 2021, the Public Health Agency of Canada launched an outbreak surveillance system, the Canadian COVID-19 Outbreak Surveillance System (CCOSS), with the goal of monitoring incidence and severity of coronavirus disease 2019 (COVID-19) outbreaks across various community settings and complementing case surveillance. Methods: Seven provinces were included in this report; these provinces submitted weekly cumulative COVID-19 outbreak line lists to CCOSS in 2021. Data includes administrative variables (e.g. date outbreak declared, date outbreak declared over, outbreak identifier), 24 outbreak settings, and number of confirmed cases and outcomes (hospitalization, death). Descriptive analyses for COVID-19 outbreaks across Canada from January 3, 2021, to January 1, 2022, were performed examining trends over time, severity, and outbreak size. Results: Incidence of outbreaks followed similar trends to case incidence. Outbreaks were most common in school and childcare settings (39%) and industrial/agricultural settings (21%). Outbreak size ranged from 2 to 639 cases per outbreak; the median size was four cases per outbreak. Correctional facilities had the largest median outbreak size with 18 cases per outbreak, followed by long-term care facilities with 10 cases per outbreak. During periods of high case incidence, outbreaks may be under-ascertained due to limited public health capacity, or reporting may be biased towards high-risk settings prioritized for testing. Outbreaks reported to CCOSS were dominated by jurisdictions with the largest populations. Conclusion: The trends illustrate that COVID-19 outbreaks in 2021 were reported most frequently in community settings such as schools; however, the largest outbreaks occurred in congregate living settings. The information gathered from outbreak surveillance complemented case incidence trends and furthered understanding of COVID-19 in Canada.

Assessment Model for Rapid Suppression of SARS-CoV-2 Transmission under Government Control.

The rapid suppression of SARS-CoV-2 transmission remains a priority for maintaining public health security throughout the world, and the agile adjustment of government prevention and control strategies according to the spread of the epidemic is crucial for controlling the spread of the epidemic. Thus, in this study, a multi-agent modeling approach was developed for constructing an assessment model for the rapid suppression of SARS-CoV-2 transmission under government control. Different from previous mathematical models, this model combines computer technology and geographic information system to abstract human beings in different states into micro-agents with self-control and independent decision-making ability; defines the rules of agent behavior and interaction; and describes the mobility, heterogeneity, contact behavior patterns, and dynamic interactive feedback mechanism of space environment. The real geospatial and social environment in Taiyuan was considered as a case study. In the implemented model, the government agent could adjust the response level and prevention and control policies for major public health emergencies in real time according to the development of the epidemic, and different intervention strategies were provided to improve disease control methods in the simulation experiment. The simulation results demonstrate that the proposed model is widely applicable, and it can not only judge the effectiveness of intervention measures in time but also analyze the virus transmission status in complex urban systems and its change trend under different intervention measures, thereby providing scientific guidance to support urban public health safety.