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1.
JAMA Netw Open ; 4(4): e218184, 2021 04 01.
Article in English | MEDLINE | ID: covidwho-1384070

ABSTRACT

Importance: Digital contact tracing (DCT) apps have been released in several countries to help interrupt SARS-CoV-2 transmission chains. However, the effect of DCT on pandemic mitigation remains to be demonstrated. Objective: To estimate key populations and performance indicators along the exposure notification cascade of the SwissCovid DCT app in a clearly defined regional and temporal context. Design, Setting, and Participants: This comparative effectiveness study was based on a simulation informed by measured data from issued quarantine recommendations and positive SARS-CoV-2 test results after DCT exposure notifications in the canton of Zurich. A stochastic model was developed to re-create the DCT notification cascade for Zurich. Population sizes at each cascade step were estimated using triangulation based on publicly available administrative and observational research data for the study duration from September 1 to October 31, 2020. The resultant estimates were checked for internal consistency and consistency with upstream or downstream estimates in the cascade. Stochastic sampling from data-informed parameter distributions was performed to explore the robustness of results. Subsequently, key performance indicators were evaluated to assess the potential contribution of DCT compared with manual contact tracing. Main Outcomes and Measures: Receiving a voluntary quarantine recommendation and/or a positive SARS-CoV-2 test result after exposure notification. Results: In September 2020, 537 app users received a positive SARS-CoV-2 test result in Zurich, 324 of whom received and entered an upload authorization code. This code triggered an app notification for an estimated 1374 (95% simulation interval [SI], 932-2586) proximity contacts and led to 722 information hotline calls, with an estimated 170 callers (95% SI, 154-186) receiving a quarantine recommendation. An estimated 939 (95% SI, 720-1127) notified app users underwent testing for SARS-CoV-2, of whom 30 (95% SI, 23-36) had positive results after an app notification. Key indicator evaluations revealed that the DCT app triggered quarantine recommendations for the equivalent of 5% of all exposed contacts placed in quarantine by manual contact tracing. For every 10.9 (95% SI, 7.6-15.6) upload authorization codes entered in the app, 1 contact had positive test results for SARS-CoV-2 after app notification. Longitudinal indicator analyses demonstrated bottlenecks in the notification cascade, because capacity limits were reached owing to an increased incidence of SARS-CoV-2 infection in October 2020. Conclusions and Relevance: In this simulation study of the notification cascade of the SwissCovid DCT app, receipt of exposure notifications was associated with quarantine recommendations and identification of SARS-CoV-2-positive cases. These findings in notified proximity contacts reflect important intermediary steps toward transmission prevention.


Subject(s)
COVID-19 , Computer Simulation , Contact Tracing , Disease Notification , Disease Transmission, Infectious , Mobile Applications , Adult , COVID-19/diagnosis , COVID-19/epidemiology , COVID-19/prevention & control , COVID-19/transmission , Communicable Disease Control/methods , Communicable Disease Control/organization & administration , Contact Tracing/methods , Contact Tracing/statistics & numerical data , Disease Notification/methods , Disease Notification/statistics & numerical data , Disease Transmission, Infectious/prevention & control , Disease Transmission, Infectious/statistics & numerical data , Female , Humans , Male , Quarantine , SARS-CoV-2/isolation & purification , Switzerland/epidemiology
3.
PLoS One ; 16(1): e0244983, 2021.
Article in English | MEDLINE | ID: covidwho-1388896

ABSTRACT

Here we look into the spread of aerosols indoors that may potentially carry viruses. Many viruses, including the novel SARS-CoV-2, are known to spread via airborne and air-dust pathways. From the literature data and our research on the propagation of fine aerosols, we simulate herein the carryover of viral aerosols in indoor air. We demonstrate that a lot of fine droplets released from an infected person's coughing, sneezing, or talking propagate very fast and for large distances indoors, as well as bend around obstacles, lift up and down over staircases, and so on. This study suggests equations to evaluate the concentration of those droplets, depending on time and distance from the source of infection. Estimates are given for the safe distance to the source of infection, and available methods for neutralizing viral aerosols indoors are considered.


Subject(s)
COVID-19/transmission , Disease Transmission, Infectious/prevention & control , Aerosols/analysis , Air Microbiology , Air Pollution, Indoor/analysis , COVID-19/metabolism , COVID-19/virology , Cough , Disease Transmission, Infectious/statistics & numerical data , Dust , Humans , Models, Theoretical , SARS-CoV-2/isolation & purification , Sneezing/physiology , Virus Diseases/prevention & control
4.
Virol J ; 18(1): 109, 2021 06 02.
Article in English | MEDLINE | ID: covidwho-1388777

ABSTRACT

BACKGROUND: The ongoing SARS-CoV-2 pandemic has spread rapidly worldwide and disease prevention is more important than ever. In the absence of a vaccine, knowledge of the transmission routes and risk areas of infection remain the most important existing tools to prevent further spread. METHODS: Here we investigated the presence of the SARS-CoV-2 virus in the hospital environment at the Uppsala University Hospital Infectious Disease ward by RT-qPCR and determined the infectivity of the detected virus in vitro on Vero E6 cells. RESULTS: SARS-CoV-2 RNA was detected in several areas, although attempts to infect Vero E6 cells with positive samples were unsuccessful. However, RNase A treatment of positive samples prior to RNA extraction did not degrade viral RNA, indicating the presence of SARS-CoV-2 nucleocapsids or complete virus particles protecting the RNA as opposed to free viral RNA. CONCLUSION: Our results show that even in places where a moderate concentration (Ct values between 30 and 38) of SARS-CoV-2 RNA was found; no infectious virus could be detected. This suggests that the SARS-CoV-2 virus in the hospital environment subsides in two states; as infectious and as non-infectious. Future work should investigate the reasons for the non-infectivity of SARS-CoV-2 virions.


Subject(s)
COVID-19/transmission , Cross Infection/epidemiology , Disease Transmission, Infectious/statistics & numerical data , Environmental Monitoring/methods , Animals , Cell Line , Chlorocebus aethiops , Confined Spaces , Cross Infection/virology , Hospitals , Humans , Risk , SARS-CoV-2/growth & development , Ventilation/methods , Vero Cells
7.
Clin Infect Dis ; 71(9): 2482-2487, 2020 12 03.
Article in English | MEDLINE | ID: covidwho-1387742

ABSTRACT

BACKGROUND: Previous reports have suggested that transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is reduced by higher temperatures and higher humidity. We analyzed case data from the United States to investigate the effects of temperature, precipitation, and ultraviolet (UV) light on community transmission of SARS-CoV-2. METHODS: Daily reported cases of SARS-CoV-2 across the United States from 22 January 2020 to 3 April 2020 were analyzed. We used negative binomial regression modeling to determine whether daily maximum temperature, precipitation, UV index, and the incidence 5 days later were related. RESULTS: A maximum temperature above 52°F on a given day was associated with a lower rate of new cases at 5 days (incidence rate ratio [IRR], 0.85 [0.76, 0.96]; P = .009). Among observations with daily temperatures below 52°F, there was a significant inverse association between the maximum daily temperature and the rate of cases at 5 days (IRR, 0.98 [0.97, 0.99]; P = .001). A 1-unit higher UV index was associated with a lower rate at 5 days (IRR, 0.97 [0.95, 0.99]; P = .004). Precipitation was not associated with a greater rate of cases at 5 days (IRR, 0.98 [0.89, 1.08]; P = .65). CONCLUSIONS: The incidence of disease declines with increasing temperature up to 52°F and is lower at warmer vs cooler temperatures. However, the association between temperature and transmission is small, and transmission is likely to remain high at warmer temperatures.


Subject(s)
COVID-19/epidemiology , Disease Transmission, Infectious/statistics & numerical data , SARS-CoV-2 , Weather , COVID-19/transmission , Humans , Incidence , Regression Analysis , Sunlight , Temperature , Ultraviolet Rays , United States/epidemiology
11.
Ann Med ; 53(1): 1569-1575, 2021 12.
Article in English | MEDLINE | ID: covidwho-1379398

ABSTRACT

OBJECTIVES: To explore the potential of SARS-CoV-2 spread during air travel and the risk of in-flight transmission. METHODS: We enrolled all passengers and crew suspected of being infected with SARS-CoV-2, who bounded for Beijing on international flights. We specified the characteristics of all confirmed cases of COVID-19 infection and utilised Wells-Riley equation to estimate the infectivity of COVID-19 during air travel. RESULTS: We screened 4492 passengers and crew with suspected COVID-19 infection, verified 161 confirmed cases (mean age 28.6 years), and traced two confirmed cases who may have been infected in the aircraft. The estimated infectivity was 375 quanta/h (range 274-476), while the effective infectivity was only 4 quanta/h (range 2-5). The risk of per-person infection during a 13 h air travel in economy class was 0.56‰ (95% CI 0.41‰-0.72‰). CONCLUSION: We found that the universal use of face masks on the flight, together with the plane's ventilation system, significantly decreased the infectivity of COVID-19.KEY MESSAGESThe COVID-19 pandemic is changing the lifestyle in the world, especially air travel which has the potential to spread SARS-CoV-2.The universal use of face masks on the flight, together with the plane's ventilation system, significantly decreased the infectivity of COVID-19 on an aircraft.Our findings suggest that the risk of infection in aircraft was negligible.


Subject(s)
Air Travel/statistics & numerical data , COVID-19/epidemiology , Disease Transmission, Infectious/statistics & numerical data , Environmental Exposure/statistics & numerical data , COVID-19/diagnosis , COVID-19/prevention & control , Disease Transmission, Infectious/prevention & control , Female , Humans , Male , Models, Theoretical , Risk Factors , Risk Reduction Behavior , SARS-CoV-2/isolation & purification
12.
PLoS One ; 16(7): e0248324, 2021.
Article in English | MEDLINE | ID: covidwho-1329132

ABSTRACT

Wearing a facial mask can limit COVID-19 transmission. Measurements of communities' mask use behavior have mostly relied on self-report. This study's objective was to devise a method to measure the prevalence of improper mask use and no mask use in indoor public areas without relying on self-report. A stratified random sample of retail trade stores (public areas) in Louisville, Kentucky, USA, was selected and targeted for observation by trained surveyors during December 14-20, 2020. The stratification allowed for investigating mask use behavior by city district, retail trade group, and public area size. The total number of visited public areas was 382 where mask use behavior of 2,080 visitors and 1,510 staff were observed. The average prevalence of mask use among observed visitors was 96%, while the average prevalence of proper use was 86%. In 48% of the public areas, at least one improperly masked visitor was observed and in 17% at least one unmasked visitor was observed. The average prevalence of proper mask use among staff was 87%, similar to the average among visitors. However, the percentage of public areas where at least one improperly masked staff was observed was 33. Significant disparities in mask use and its proper use were observed among both visitors and staff by public area size, retail trade type, and geographical area. Observing unmasked and improperly masked visitors was more common in small (less than 1500 square feet) public areas than larger ones, specifically in food and grocery stores as compared to other retail stores. Also, the majority of the observed unmasked persons were male and middle-aged.


Subject(s)
COVID-19/prevention & control , Masks/statistics & numerical data , COVID-19/epidemiology , COVID-19/transmission , Disease Transmission, Infectious/prevention & control , Disease Transmission, Infectious/statistics & numerical data , Humans , Kentucky/epidemiology , Pandemics , Prevalence , Public Facilities , Public Health/methods , SARS-CoV-2/isolation & purification
14.
PLoS One ; 16(7): e0253758, 2021.
Article in English | MEDLINE | ID: covidwho-1315885

ABSTRACT

BACKGROUND: Governments across the globe responded with different strategies to the COVID-19 pandemic. While some countries adopted measures, which have been perceived controversial, others pursued a strategy aiming for herd immunity. The latter is even more controversial and has been called unethical by the WHO Director-General. Inevitably, without proper control measures, viral diversity increases and multiple infectious exposures become common, when the pandemic reaches its maximum. This harbors not only a potential threat overseen by simplified theoretical arguments in support of herd immunity, but also deserves attention when assessing response measures to increasing numbers of infection. METHODS AND FINDINGS: We extend the simulation model underlying the pandemic preparedness web interface CovidSim 1.1 (http://covidsim.eu/) to study the hypothetical effect of increased morbidity and mortality due to 'multi-infections', either acquired at by successive infective contacts during the course of one infection or by a single infective contact with a multi-infected individual. The simulations are adjusted to reflect roughly the situation in the USA. We assume a phase of general contact reduction ("lockdown") at the beginning of the epidemic and additional case-isolation measures. We study the hypothetical effects of varying enhancements in morbidity and mortality, different likelihoods of multi-infected individuals to spread multi-infections and different susceptibility to multi-infections in different disease phases. It is demonstrated that multi-infections lead to a slight reduction in the number of infections, as these are more likely to get isolated due to their higher morbidity. However, the latter substantially increases the number of deaths. Furthermore, simulations indicate that a potential second lockdown can substantially decrease the epidemic peak, the number of multi-infections and deaths. CONCLUSIONS: Enhanced morbidity and mortality due to multiple disease exposure is a potential threat in the COVID-19 pandemic that deserves more attention. Particularly it underlines another facet questioning disease management strategies aiming for herd immunity.


Subject(s)
COVID-19/epidemiology , Disease Transmission, Infectious/statistics & numerical data , Immunity, Herd , COVID-19/immunology , COVID-19/mortality , COVID-19/transmission , Humans , Models, Statistical , Mortality/trends
15.
PLoS One ; 16(7): e0254012, 2021.
Article in English | MEDLINE | ID: covidwho-1311284

ABSTRACT

BACKGROUND: In response to the spread of the coronavirus disease 2019 (COVID-19), plenty of control measures were proposed. To assess the impact of current control measures on the number of new case indices 14 countries with the highest confirmed cases, highest mortality rate, and having a close relationship with the outbreak's origin; were selected and analyzed. METHODS: In the study, we analyzed the impact of five control measures, including centralized isolation of all confirmed cases, closure of schools, closure of public areas, closure of cities, and closure of borders of the 14 targeted countries according to their timing; by comparing its absolute effect average, its absolute effect cumulative, and its relative effect average. RESULTS: Our analysis determined that early centralized isolation of all confirmed cases was represented as a core intervention in significantly disrupting the pandemic's spread. This strategy helped in successfully controlling the early stage of the outbreak when the total number of cases were under 100, without the requirement of the closure of cities and public areas, which would impose a negative impact on the society and its economy. However, when the number of cases increased with the apparition of new clusters, coordination between centralized isolation and non-pharmaceutical interventions facilitated control of the crisis efficiently. CONCLUSION: Early centralized isolation of all confirmed cases should be implemented at the time of the first detected infectious case.


Subject(s)
COVID-19/prevention & control , Patient Isolation/statistics & numerical data , Quarantine/statistics & numerical data , COVID-19/transmission , Disease Notification/statistics & numerical data , Disease Transmission, Infectious/statistics & numerical data , Humans , Models, Statistical
16.
JSLS ; 25(2)2021.
Article in English | MEDLINE | ID: covidwho-1305863

ABSTRACT

Background and Objectives: Operating-room procedures canceled due to the COVID-19 pandemic depleted hospital revenue and potentially worsened patient outcomes through disease progression. Despite safeguards to resume elective procedures, patients remain apprehensive of contracting COVID-19 during hospitalization and recovery. We investigated symptomatic COVID-19 infection in patients undergoing operating-room procedures during the spring 2020 outbreak in Fairfield County, CT, a heavily affected New York Metropolitan area. Methods: We retrospectively analyzed 419 operating-room patients in Danbury and Norwalk Hospitals between 3/16/20 and 5/19/20. COVID-19 infection was assessed through test results or documented well-being within 2 weeks postdischarge. Variables studied were procedure classification, length of stay, and discharge disposition. Postprocedural COVID-19 infection was analyzed using binomial tests comparing rates to state-mandated infection data. Results: Six patients developed COVID-19 after 212 urgent-elective and 207 emergent procedures. Overall postprocedural infection risk was equivalent to community infection risk (P > .05). No infections occurred in 1-2 day stays or urgent-elective procedures with discharge home (both P < .05). Discharges home reduced the risk to one-sixth of community spread (P = .03). Risk of infection doubled in hospitalizations > 5 days (P = .05) and quadrupled in discharges to extended care facilities (P = .01). Discussion: Operating-room procedures did not increase the risk of symptomatic COVID-19 infection during an outbreak. Urgent-elective and emergent procedures during further outbreaks appear safe when anticipating short stays with discharges home. When anticipating prolonged hospitalization or discharges to facilities, appropriate delay of urgent-elective procedures may minimize risk of infection.


Subject(s)
COVID-19/epidemiology , Cross Infection/epidemiology , Disease Transmission, Infectious/statistics & numerical data , Elective Surgical Procedures/adverse effects , Patient Discharge/statistics & numerical data , Postoperative Complications/epidemiology , Aged , Aged, 80 and over , COVID-19/transmission , Connecticut/epidemiology , Cross Infection/virology , Female , Humans , Male , Middle Aged , New York City/epidemiology , Operating Rooms , Postoperative Complications/virology , Retrospective Studies , SARS-CoV-2
19.
JAMA Netw Open ; 4(6): e2113818, 2021 06 01.
Article in English | MEDLINE | ID: covidwho-1274645

ABSTRACT

Importance: Limited information on the transmission and dynamics of SARS-CoV-2 at the city scale is available. Objective: To describe the local spread of SARS-CoV-2 in Valencia, Spain. Design, Setting, and Participants: This single-center epidemiological cohort study of patients with SARS-CoV-2 was performed at University General Hospital in Valencia (population in the hospital catchment area, 364 000), a tertiary hospital. The study included all consecutive patients with COVID-19 isolated at home from the start of the COVID-19 pandemic on February 19 until August 31, 2020. Exposures: Cases of SARS-CoV-2 infection confirmed by the presence of IgM antibodies or a positive polymerase chain reaction test result on a nasopharyngeal swab were included. Cases in which patients with negative laboratory results met diagnostic and clinical criteria were also included. Main Outcomes and Measures: The primary outcome was the characterization of dissemination patterns and connections among the 20 neighborhoods of Valencia during the outbreak. To recreate the transmission network, the inbound and outbound connections were studied for each region, and the relative risk of infection was estimated. Results: In total, 2646 patients were included in the analysis. The mean (SD) age was 45.3 (22.5) years; 1203 (46%) were male and 1442 (54%) were female (data were missing for 1); and the overall mortality was 3.7%. The incidence of SARS-CoV-2 cases was higher in neighborhoods with higher household income (ß2 [for mean income per household] = 0.197; 95% CI, 0.057-0.351) and greater population density (ß1 [inhabitants per km2] = 0.228; 95% CI, 0.085-0.387). Correlations with meteorological variables were not statistically significant. Neighborhood 3, where the hospital and testing facility were located, had the most outbound connections (14). A large residential complex close to the city (neighborhood 20) had the fewest connections (0 outbound and 2 inbound). Five geographically unconnected neighborhoods were of strategic importance in disrupting the transmission network. Conclusions and Relevance: This study of local dissemination of SARS-COV-2 revealed nonevident transmission patterns between geographically unconnected areas. The results suggest that tailor-made containment measures could reduce transmission and that hospitals, including testing facilities, play a crucial role in disease transmission. Consequently, the local dynamics of SARS-CoV-2 spread might inform the strategic lockdown of specific neighborhoods to stop the contagion and avoid a citywide lockdown.


Subject(s)
COVID-19/epidemiology , Catchment Area, Health/statistics & numerical data , Disease Outbreaks/statistics & numerical data , Disease Transmission, Infectious/statistics & numerical data , Residence Characteristics/statistics & numerical data , Adult , Aged , Aged, 80 and over , COVID-19/transmission , Cohort Studies , Female , Geography , Humans , Incidence , Male , Middle Aged , Risk Factors , SARS-CoV-2 , Spain/epidemiology
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