Implementation and Evolution of Mitigation Measures, Testing, and Contact Tracing in the National Football League, August 9-November 21, 2020.

The National Football League (NFL) and the NFL Players Association (NFLPA) began the 2020 football season in July, implementing extensive mitigation and surveillance measures in facilities and during travel and gameplay. Mitigation protocols* were evaluated and modified based on data from routine reverse transcription-polymerase chain reaction (RT-PCR) tests for SARS-CoV-2, the virus that causes coronavirus 2019 (COVID-19); proximity tracking devices; and detailed interviews. Midseason, transmission was observed in persons who had cumulative interactions of <15 minutes' duration, leading to a revised definition of high-risk contacts that required consideration of mask use, setting and room ventilation in addition to proximity and duration of interaction. The NFL also developed an intensive protocol that imposed stricter infection prevention precautions when a case was identified at an NFL club. The intensive protocol effectively prevented the occurrence of high-risk interactions, with no high-risk contacts identified for 71% of traced cases at clubs under the intensive protocol. The incorporation of the nature and location of the interaction, including mask use, indoor versus outdoor setting, and ventilation, in addition to proximity and duration, likely improved identification of exposed persons at higher risk for SARS-CoV-2 infection. Quarantine of these persons, along with testing and intensive protocols, can reduce spread of infection.

Pilot Investigation of SARS-CoV-2 Secondary Transmission in Kindergarten Through Grade 12 Schools Implementing Mitigation Strategies - St. Louis County and City of Springfield, Missouri, December 2020.

Many kindergarten through grade 12 (K-12) schools offering in-person learning have adopted strategies to limit the spread of SARS-CoV-2, the virus that causes COVID-19 (1). These measures include mandating use of face masks, physical distancing in classrooms, increasing ventilation with outdoor air, identification of close contacts,* and following CDC isolation and quarantine guidance† (2). A 2-week pilot investigation was conducted to investigate occurrences of SARS-CoV-2 secondary transmission in K-12 schools in the city of Springfield, Missouri, and in St. Louis County, Missouri, during December 7-18, 2020. Schools in both locations implemented COVID-19 mitigation strategies; however, Springfield implemented a modified quarantine policy permitting student close contacts aged ≤18 years who had school-associated contact with a person with COVID-19 and met masking requirements during their exposure to continue in-person learning.§ Participating students, teachers, and staff members with COVID-19 (37) from 22 schools and their school-based close contacts (contacts) (156) were interviewed, and contacts were offered SARS-CoV-2 testing. Among 102 school-based contacts who received testing, two (2%) had positive test results indicating probable school-based SARS-CoV-2 secondary transmission. Both contacts were in Springfield and did not meet criteria to participate in the modified quarantine. In Springfield, 42 student contacts were permitted to continue in-person learning under the modified quarantine; among the 30 who were interviewed, 21 were tested, and none received a positive test result. Despite high community transmission, SARS-CoV-2 transmission in schools implementing COVID-19 mitigation strategies was lower than that in the community. Until additional data are available, K-12 schools should continue implementing CDC-recommended mitigation measures (2) and follow CDC isolation and quarantine guidance to minimize secondary transmission in schools offering in-person learning.

Emissions, airflow patterns and modeling of test compounds in controlled hospital environments.

Spreading and distribution of selected volatile organic compounds (VOCs) released as point source emissions in a hospital environment were investigated in two office rooms and two patient rooms. Six tracer compounds were released from six locations and their concentrations were measured in five sampling sites during two consecutive days. The air flow rates, velocity and flow direction, air temperature, pressure differences between adjacent rooms, and relative humidity and concentrations of the tracer compounds were measured. The results revealed that the size of the examined space and ventilation rates, the monitoring point should be either close to the exhaust terminal device or in the middle of the occupied zone the way that supply air flows do not interfere the measurements. Depending on the inlet terminal device and its location, the air is either delivered parallel to the ceiling or it can be directed to a desired spot into the occupied zone. The tracer compounds did spread evenly within the room and their concentrations decreased inversely with the distance. In rooms with a good ventilation, the concentrations at the exhaust air terminal units were close to those measured near the source point. The results obtained from modeling were consistent with the measurements.

Measuring ventilation in different typologies of rural Gambian houses: a pilot experimental study.

BACKGROUND: African houses are frequently too hot and uncomfortable to use a bed net at night. Indoor thermal comfort is often evaluated by measuring temperature and humidity, ignoring ventilation. This study explored ways to measure ventilation in single-roomed rural Gambian houses during the malaria transmission season and evaluated building designs that could increase airflow at night and help keep the occupants comfortable. METHODS: Two identical mud-walled houses were constructed with a metal roof, three doors and closed eaves. Experiment 1 compared five methods for measuring ventilation in a building: (1) using a blower door, (2) increasing carbon dioxide (CO2) levels indoors using an artificial source of CO2 and then measuring the rate of gas decay, (3) using a similar approach with a natural source of CO2, (4) measuring the rise of CO2 when people enter a building and (5) using hot-wire anemometers. Experiment 2 used CO2 data loggers to compare ventilation in a reference metal-roofed house with closed eaves and badly-fitting doors with a similar house with (1) thatched roof and open eaves, (2) eaves tubes, (3) screened doors and (4) screened doors and windows. RESULTS: In experiment 1, CO2 data loggers placed indoors in two identical houses showed similar changes in airflow (p > 0.05) for all three methods recording either decreasing or increasing CO2. Blower doors were unable to measure airflow in houses with open eaves or screened windows and the anemometers broke down under field conditions. In experiment 2, open eaves in thatched houses, screened doors alone, and screened doors and windows increased indoor ventilation compared to the reference metal-roofed house with closed eaves and badly fitting doors (p < 0.05). Eaves tubes did not increase ventilation in comparison to the reference house. CONCLUSION: CO2 data loggers proved to be a simple and efficient method for measuring ventilation in rural houses at night. Ventilation of metal-roofed houses can be improved by adding two screened doors and windows on opposite walls. Improved ventilation will result in increased thermal comfort making it more likely that people will sleep under a bed net.

Birth month is associated with learning capacity in childhood in Northeast China.

It is difficult to evaluate long-term ventilation and indoor-outdoor temperature variation on-site in the birth residence so as to investigate their associations with learning capacity from childhood through adolescence. Here, we conducted a questionnaire-based retrospective cohort study in ten schools from two northeast China cities with warm summers and severe cold winters when residences had very low air exchange rates. Scores for Chinese, Mathematics, and English in the final exams of the summer semester in June 2018 were collected to evaluate learning capacity. We surveyed 6238 students aged 14.7 (SD: 2.1) years old. Using the 2nd quarter (April-May-June) birth as reference, 4th quarter (October-November-December) birth consistently was significantly associated with lower scores in Chinese in bivariate (ß, 95%CI: -3.2, -4.3 to -2.0) and multivariate (-1.8, -2.4 to -0.8) linear regression analyses. Stratified sub-analyses showed significant associations for male (-2.4, -3.7 to -1.1), urban (-2.4, -3.4 to -1.4), and primary students (-2.9, -4.5 to -1.4). Since household ventilation and indoor-outdoor temperature variation had great differences between the 2nd and 4th quarter of year, our results suggest that these two factors in the birth residence could be associated with learning capacity in childhood, especially for male and primary students in northeast China.

Analysis of pre- and intraoperative clinical for successful operating room extubation after living donor liver transplantation: a retrospective observational cohort study.

BACKGROUND: Early extubation after liver transplantation is safe and accelerates patient recovery. Patients with end-stage liver disease undergo sarcopenic changes, and sarcopenia is associated with postoperative morbidity and mortality. We investigated the impact of core muscle mass on the feasibility of immediate extubation in the operating room (OR) after living donor liver transplantation (LDLT). METHODS: A total of 295 male adult LDLT patients were retrospectively reviewed between January 2011 and December 2017. In total, 40 patients were excluded due to emergency surgery or severe encephalopathy. A total of 255 male LDLT patients were analyzed in this study. According to the OR extubation criteria, the study population was classified into immediate and conventional extubation groups (39.6 vs. 60.4%). Psoas muscle area was estimated using abdominal computed tomography and normalized by height squared (psoas muscle index [PMI]). RESULTS: There were no significant differences in OR extubation rates among the five attending transplant anesthesiologists. The preoperative PMI correlated with respiratory performance. The preoperative PMI was higher in the immediate extubation group than in the conventional extubation group. Potentially significant perioperative factors in the univariate analysis were entered into a multivariate analysis, in which preoperative PMI and intraoperative factors (i.e., continuous renal replacement therapy, significant post-reperfusion syndrome, and fresh frozen plasma transfusion) were associated with OR extubation. The duration of ventilator support and length of intensive care unit stay were shorter in the immediate extubation group than in the conventional extubation group, and the incidence of pneumonia and early allograft dysfunction were also lower in the immediate extubation group. CONCLUSIONS: Our study could improve the accuracy of predictions concerning immediate post-transplant extubation in the OR by introducing preoperative PMI into predictive models for patients who underwent elective LDLT.

How home ventilation rates affect health: A literature review.

This paper reviews studies of the relationships between ventilation rates (VRs) in homes and occupant health, primarily respiratory health. Five cross-sectional studies, seven case-control studies, and eight intervention studies met inclusion criteria. Nearly all studies controlled for a range of potential confounders and most intervention studies included placebo conditions. Just over half of studies reported one or more statistically significant (SS) health benefits of increased VRs. Wheeze was most clearly associated with VR. No health outcomes had SS associations with VRs in the majority of statistical tests. Most studies that reported SS health benefits from increased VRs also had additional health outcomes that did not improve with increased VRs. Overall, the number of SS improvements in health with increased VRs exceeded the anticipated chance improvements by approximately a factor of seven. The magnitude of the improvements in health outcomes with increased VRs ranged from 20% to several-fold improvements. In summary, the available research indicates a tendency for improvements in respiratory health with increased home VRs; however, health benefits do not occur consistently and other exposure control measures should be used together with ventilation. The research did not enable identification of a threshold VR below which adverse health effects occur.

Residential inter-zonal ventilation rates for exposure modeling.

Residential inter-zonal (e.g., between rooms) ventilation is comprised of fresh air infiltration in and exfiltration out of the whole house plus the "fresh" air that is entering (and exiting) the room of interest from other rooms or areas within the house. Clearly, the inter-zone ventilation rate in any room of interest will be greater than the infiltration/exfiltration ventilation rate of outdoor air for the whole house. The purpose of this study is to determine how much greater the inter-zonal ventilation rate is in typical U.S. residences compared to the whole house ventilation rate from outdoor air. The data for this statistical analysis came from HouseDB, a 1995 EPA database of residential ventilation rates. Analytical results indicate that a lognormal distribution provides the best fit to the data. Lognormal probability distribution functions (PDFs) are provided for various inter-zonal ventilation rates for comparison to the PDF for the whole house ventilation rates. All ventilation rates are expressed as air change rates per hour (ACH). These PDFs can be used as inputs to exposure models. This analysis suggests that if one were performing a deterministic analysis for unknown housing stocks in the U.S., a default mean and median ACH values of 0.4/hr and 0.3/hr, respectively, for whole house ventilation would be appropriate; and 0.7/hr and 0.6/hr, respectively, for inter-zonal ventilation.

The ventilation problem in schools: literature review.

Based on a review of literature published in refereed archival journals, ventilation rates in classrooms often fall far short of the minimum ventilation rates specified in standards. There is compelling evidence, from both cross-sectional and intervention studies, of an association of increased student performance with increased ventilation rates. There is evidence that reduced respiratory health effects and reduced student absence are associated with increased ventilation rates. Increasing ventilation rates in schools imposes energy costs and can increase heating, ventilating, and air-conditioning system capital costs. The net annual costs, ranging from a few dollars to about 10 dollars per person, are less than 0.1% of typical public spending on elementary and secondary education in the United States. Such expenditures seem like a small price to pay given the evidence of health and performance benefits.

SBS symptoms in relation to dampness and ventilation in inspected single-family houses in Sweden.

PURPOSE: To investigate the relationships between symptoms compatible with the sick building syndrome (SBS) in adults and building dampness and ventilation in single-family houses. METHODS: Within the Swedish BETSI study, a national sample of single-family houses were inspected by professional building experts, and adults living in the houses answered a questionnaire on SBS. Relationships between building factors and SBS were analysed using logistic regression. RESULTS: Of the respondents, 23% reported having had weekly SBS symptoms during the last three months. A large proportion of houses exhibited building or construction problems. In total, 40% of houses had dampness problems in the foundation, and this was related to a higher prevalence of both mucous and dermal symptoms, and any SBS symptoms. Furthermore, high air humidity was related to more symptoms, with the relationship with absolute humidity being stronger than that with relative humidity or moisture load. Symptoms were also more prevalent in houses with a high U value, reflecting a poor thermal insulation. Compared to natural ventilation, living in a house with mechanical supply and exhaust ventilation was related to a lower prevalence of general symptoms and any SBS symptoms, but there were only weak associations between measured air exchange rate and symptoms. CONCLUSIONS: A large proportion of single-family houses have dampness problems in the foundation, and pollutants may enter the living space of the house and affect the health of the occupants. Furthermore, absolute air humidity should be measured more often in indoor air studies.

Evaluation of the well mixed room and near-field far-field models in occupational settings.

Drawing appropriate conclusions about a scenario for which the exposure is truly unacceptable drives appropriate exposure and risk management, and protects the health and safety of those individuals. To ensure the vast majority of these decisions are accurate, these decisions must be based upon proven approaches and tools. When these decisions are based solely on professional judgment guided by subjective inputs, however, they are more than likely wrong, and biased, underestimating the true exposure. Models have been shown anecdotally to be useful in accurately predicting exposure but their use in occupational hygiene has been limited. Possible reasons are a general lack of guidance on model selection and use and scant model input data. The lack of systematic evaluation of the models is also an important factor. This research is the second phase of work building upon the robust evaluation of the Well Mixed Room (WMR) and Near Field Far Field (NF-FF) models under controlled conditions in an exposure chamber, [5] in which good concordance between measured and modeled airborne concentrations of three solvents under a range of conditions was observed. In real world environments, the opportunity to control environmental conditions is limited and measuring the model inputs directly can be challenging; in many cases, model inputs must be estimated indirectly without measurement. These circumstances contribute to increased model input uncertainty and consequent uncertainty in the output. Field studies of model performance directly inform us about how well models predict exposures given these practical limitations, and are, therefore, an important component of model evaluation. The evaluation included ten diverse contaminant-exposure scenarios at five workplaces involving six different contaminants. A database of parameter values and measured and modeled exposures was developed and will be useful for modeling similar scenarios in the future.

Medical interventions and survival by gender of children with trisomy 18.

Research has typically shown limited aggressive medical interventions and low survival rates for children with full trisomy 18. Recent studies provide more positive results. This study examined 82 children with full trisomy 18 drawn from the Tracking Rare Incidence Syndromes (TRIS) project database. Children were classified into three groups according to the highest intervention received: "hospice or no intervention" (n = 5, 6.1%), "necessary interventions (enteral feeding, ventilator use)" (n = 46, 56.1%), and "aggressive interventions (surgery)" (n = 31, 37.8%). Seven of 14 male children (50%) and 52 of 68 female children (76.5%) were living at the time of survey completion. Additionally, information about any interventions used during the care of these children was also provided. It was found that three males (37.5%) and 28 females (48.3%) had used hospice care at some point; 12 males (85.7%) and 61 females (89.7%) received enteral feeding at some point; 7 males (58.3%) and 25 females (38.5%) had ventilator; and 7 males (50%) and 33 females (48.5%) underwent some form of surgery. These results suggest improved outcomes when given necessary and aggressive medical interventions. Implications and recommendations for further research are provided. © 2016 Wiley Periodicals, Inc.

Perceptions in the U.S. building industry of the benefits and costs of improving indoor air quality.

How building stakeholders (e.g. owners, tenants, operators, and designers) understand impacts of Indoor Air Quality (IAQ) and associated energy costs is unknown. We surveyed 112 stakeholders across the United States to ascertain their perceptions of their current IAQ and estimates of benefits and costs of, as well as willingness to pay for, IAQ improvements. Respondents' perceived IAQ scores correlated with the use of high-efficiency filters but not with any other IAQ-improving technologies. We elicited their estimates of the impacts of a ventilation-filtration upgrade (VFU), that is, doubling the ventilation rate from 20 to 40 cfm/person (9.5 to 19 l/s/person) and upgrading from a minimum efficiency reporting value 6 to 11 filter, and compared responses to estimates derived from IAQ literature and energy modeling. Minorities of respondents thought the VFU would positively impact productivity (45%), absenteeism (23%), or health (39%). Respondents' annual VFU cost estimates (mean = $257, s.d. = $496, median = $75 per person) were much higher than ours (always <$32 per person), and the only yearly cost a plurality of respondents said they would pay for the VFU was $15 per person. Respondents holding green building credentials were not more likely to affirm the IAQ benefits of the VFU and were less likely to be willing to pay for it.

Ventilation in day care centers and sick leave among nursery children.

Several studies have reported poor indoor air quality (IAQ) in day care centers (DCCs), and other studies have shown that children attending them have an increased risk of respiratory and gastrointestinal infections. The aim of this study was to investigate whether there is an association between ventilation in DCCs and sick leave among nursery children. Data on child sick leave within an 11-week period were obtained for 635 children attending 20 DCCs. Ventilation measurements included three proxies of ventilation: air exchange rate (ACR) measured with the decay method, ACR measured by the perfluorocarbon tracer gas (PFT) method, and CO2 concentration measured over a 1-week period. All but two DCCs had balanced mechanical ventilation system, which could explain the low CO2 levels measured. The mean concentration of CO2 was 643 ppm, exceeding 1000 ppm in only one DCC. A statistically significant inverse relationship between the number of sick days and ACR measured with the decay method was found for crude and adjusted analysis, with a 12% decrease in number of sick days per hour increase in ACR measured with the decay method. This study suggests a relationship between sick leave among nursery children and ventilation in DCCs, as measured with the decay method.

Do classroom ventilation rates in California elementary schools influence standardized test scores? Results from a prospective study.

Limited evidence has associated lower ventilation rates (VRs) in schools with reduced student learning or achievement. We analyzed longitudinal data collected over two school years from 150 classrooms in 28 schools within three California school districts. We estimated daily classroom VRs from real-time indoor carbon dioxide measured by web-connected sensors. School districts provided individual-level scores on standard tests in Math and English, and classroom-level demographic data. Analyses assessing learning effects used two VR metrics: average VRs for 30 days prior to tests, and proportion of prior daily VRs above specified thresholds during the year. We estimated relationships between scores and VR metrics in multivariate models with generalized estimating equations. All school districts had median school-year VRs below the California VR standard. Most models showed some positive associations of VRs with test scores; however, estimates varied in magnitude and few 95% confidence intervals excluded the null. Combined-district models estimated statistically significant increases of 0.6 points (P = 0.01) on English tests for each 10% increase in prior 30-day VRs. Estimated increases in Math were of similar magnitude but not statistically significant. Findings suggest potential small positive associations between classroom VRs and learning.

Estimated effect of ventilation and filtration on chronic health risks in U.S. offices, schools, and retail stores.

We assessed the chronic health risks from inhalation exposure to volatile organic compounds (VOCs) and particulate matter (PM2.5) in U.S. offices, schools, grocery, and other retail stores and evaluated how chronic health risks were affected by changes in ventilation rates and air filtration efficiency. Representative concentrations of VOCs and PM2.5 were obtained from available data. Using a mass balance model, changes in exposure to VOCs and PM2.5 were predicted if ventilation rate were to increase or decrease by a factor of two, and if higher efficiency air filters were used. Indoor concentrations were compared to health guidelines to estimate percentage exceedances. The estimated chronic health risks associated with VOC and PM2.5 exposures in these buildings were low relative to the risks from exposures in homes. Chronic health risks were driven primarily by exposures to PM2.5 that were evaluated using disease incidence of mortality, chronic bronchitis, and non-fatal stroke. The leading cancer risk factor was exposure to formaldehyde. Using disability-adjusted life years (DALYs) to account for both cancer and non-cancer effects, results suggest that increasing ventilation alone is ineffective at reducing chronic health burdens. Other strategies, such as pollutant source control and the use of particle filtration, should also be considered.

Indoor air quality in Portuguese schools: levels and sources of pollutants.

Indoor air quality (IAQ) parameters in 73 primary classrooms in Porto were examined for the purpose of assessing levels of volatile organic compounds (VOCs), aldehydes, particulate matter, ventilation rates and bioaerosols within and between schools, and potential sources. Levels of VOCs, aldehydes, PM2.5 , PM10 , bacteria and fungi, carbon dioxide (CO2 ), carbon monoxide, temperature and relative humidity were measured indoors and outdoors and a walkthrough survey was performed concurrently. Ventilation rates were derived from CO2 and occupancy data. Concentrations of CO2 exceeding 1000 ppm were often encountered, indicating poor ventilation. Most VOCs had low concentrations (median of individual species <5 µg/m(3) ) and were below the respective WHO guidelines. Concentrations of particulate matter and culturable bacteria were frequently higher than guidelines/reference values. The variability of VOCs, aldehydes, bioaerosol concentrations, and CO2 levels between schools exceeded the variability within schools. These findings indicate that IAQ problems may persist in classrooms where pollutant sources exist and classrooms are poorly ventilated; source control strategies (related to building location, occupant behavior, maintenance/cleaning activities) are deemed to be the most reliable for the prevention of adverse health consequences in children in schools.

Assessment of ventilation and indoor air pollutants in nursery and elementary schools in France.

The aim of this study was to characterize the relationship between Indoor Air Quality (IAQ) and ventilation in French classrooms. Various parameters were measured over one school week, including volatile organic compounds, aldehydes, particulate matter (PM2.5 mass concentration and number concentration), carbon dioxide (CO2 ), air temperature, and relative humidity in 51 classrooms at 17 schools. The ventilation was characterized by several indicators, such as the air exchange rate, ventilation rate (VR), and air stuffiness index (ICONE), that are linked to indoor CO2 concentration. The influences of the season (heating or non-heating), type of school (nursery or elementary), and ventilation on the IAQ were studied. Based on the minimum value of 4.2 l/s per person required by the French legislation for mechanically ventilated classrooms, 91% of the classrooms had insufficient ventilation. The VR was significantly higher in mechanically ventilated classrooms compared with naturally ventilated rooms. The correlations between IAQ and ventilation vary according to the location of the primary source of each pollutant (outdoor vs. indoor), and for an indoor source, whether it is associated with occupant activity or continuous emission.