High-risk Contacts Research Articles

Commentary: Potential transmissibility of SARS-CoV-2 infection via donor corneal tissue.

Commentary: Potential transmissibility of SARS-CoV-2 infection via donor corneal tissue.

Ocular Manifestations of Patients with Coronavirus Disease 2019: A Comprehensive Review.

Apart from conjunctival involvement which is the most well-known ocular manifestation of coronavirus infectious disease 2019 (COVID-19), there are multiple reports of the involvement of other ocular structures by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We comprehensively reviewed PubMed, Scopus, Embase, and Google Scholar for available evidence regarding COVID-19 various ocular manifestations, with special focus on less known and unusual ocular findings. We then categorized the findings based on the parts of the eye which was involved. In anterior sections of the eye, the involvement of the eyelid (tarsadenitis), conjunctiva and cornea (follicular conjunctivitis, pseudomembranous conjunctivitis, and keratoconjunctivitis), episclera (nodular episcleritis), uvea (anterior uveitis) were reported. Also, third, fourth, and sixth nerve palsy, retinal vasculitis, retinal optical coherence tomography (OCT) changes (hyper-reflective lesions and increased retinal nerve fiber layer thickness [RNFLT]), optic neuritis, papillophlebitis, Miller Fisher syndrome, posterior reversible leukoencephalopathy (PRES), ophthalmic artery and central retinal artery occlusion, and polyneuritis cranialis were reported in different studies. Postmortem evaluation of COVID-19 patients detected no viral RNA in different anterior and posterior segments of the eyes. However, another study revealed a 21.4% positivity of the retinal biopsies of dead patients. The results of this study can help ophthalmologists to be vigilant when they see these findings in a suspected case of COVID-19. In addition, wearing face masks and protective goggles or eye shields are recommended, especially in high risk contacts.

Assessment of COVID-19 Risky Contact of Healthcare Workers in an University Hospital

Healthcare workers are the group with the highest risk of COVID-19 transmission. The illness of healthcare workers poses a risk to patients admitted to the hospital, colleagues and households besides their own health. In this study, it was aimed to determine the risk assessment and the factors associated with risk status of an university hospital healthcare workers after risky COVID-19 contact. The data of the descriptive study were obtained from 773 follow-up records of 555 healthcare workers who applied with COVID-19 risky contact between 06.04-10.05.2020. Employees who were positive for RT-PCR evaluated as "patients" and others as "risky contact". Risk assessment was classified as no risk, low, medium and high risk contact according to the "Algorithm of Assessment of Health Workers with COVID-19 Contact" of the Ministry of Health. The relationship between the risk levels of the participants and their demographic and workplace characteristics and their usage of personal protection were evaluated. Mean, standard deviation, percentage, chi-square and ANOVA tests were used in the analysis of the data. The average age of the healthcare workers was determined as 34.4 ± 7.6 years. It was determined that 56.2% of those who had contact were female, 62.9% were married and 17.5% had an additional disease. It was determined that 45.6% of the risky contacts were nurses, 18.4% were supportive personnel and 16.9% were doctors. While 46.5% of the contacts were found as medium, 28.0% low, 17.1% high risk and 8.4% risk free. 38.2% of risky contacts occurred while working in internal/surgical clinics. While 66.0% of the employees had risky contact during patient care and treatment, 25% had risky contact with colleagues in social settings. High-risk contact was higher in social relations between employees. The source of the contact was a colleague in 73.2% of the employees. The average age of high-risk employees was smaller than those of low-risk. While 54.5% of the employees wore surgical masks during contact, 67.8% of the patients did not have a mask. Of 555 employees followed, 37 (6.7%) were diagnosed as COVID-19; 48.6% of the patients were nurses and 18.9% were doctors. It was determined that 48.6% of the healthcare workers were working in the COVID-19 service, outpatient clinic or intensive care unit at the time of diagnosis. The source of the infection was thought to be a colleague in 51.6% of the patients. COVID-19 was more common in nurses and doctors. It was determined that risky contact also occurred in services other than the units where COVID-19 patients were treated and risky contact often took place while providing healthcare to the patients and during social relations between the employees. Unprotected contact of the employees with each other in the workplace was identified as an important risk source. Inadequate use of personal protective equipment by healthcare workers led to an increase in medium and high risk contacts. The use of masks by patients and their relatives during the health service delivery and the proper use of personal protective equipment by healthcare professionals will reduce the risk. With the physical improvement of the rest areas of the employees and the arrangement of the breaks, the risky contact between colleagues in the social areas will be reduced.

Screening around a COVID-19 cluster: Exploring its impact on a local virus outbreak

ObjectiveIn March 2020, we implemented screening of the contacts of a COVID-19 cluster having occurred in the Lot-et-Garonne department, the first department of the Nouvelle-Aquitaine region to be affected by the active circulation of SARS-CoV-2. We aimed to describe the impact of this screening on the local SARS-CoV-2 outbreak. MethodsAll high-risk contacts, as well as the individuals living in their households, were screened. We detailed the evolution of the number of confirmed COVID-19 cases in the Lot-et-Garonne department and the rest of the Nouvelle-Aquitaine region. ResultsAmong the 89 screened individuals, 10 new cases were confirmed, including 4 asymptomatic persons. In Lot-et-Garonne, the number of confirmed COVID-19 cases immediately decreased after this screening and no epidemic peak occurred, contrary to what was observed in the rest of the region. ConclusionThe early screening of high-risk contacts of COVID-19 cases and members of their household implemented a few days before the first lockdown probably helped to prevent the spread of the virus in the department.

Effectiveness of Preventive Therapy for Persons Exposed at Home to Drug-Resistant Tuberculosis, Karachi, Pakistan

In Karachi, Pakistan, a South Asian megacity with a high prevalence of tuberculosis (TB) and low HIV prevalence, we assessed the effectiveness of fluoroquinolone-based preventive therapy for drug-resistant (DR) TB exposure. During February 2016–March 2017, high-risk household contacts of DR TB patients began a 6-month course of preventive therapy with a fluoroquinolone-based, 2-drug regimen. We assessed effectiveness in this cohort by comparing the rate and risk for TB disease over 2 years to the rates and risks reported in the literature. Of 172 participants, TB occurred in 2 persons over 336 person-years of observation. TB disease incidence rate observed in the cohort was 6.0/1,000 person-years. The incidence rate ratio ranged from 0.29 (95% CI 0.04–1.3) to 0.50 (95% CI 0.06–2.8), with a pooled estimate of 0.35 (95% CI 0.14–0.87). Overall, fluoroquinolone-based preventive therapy for DR TB exposure reduced risk for TB disease by 65%.

Implementation, adherence, and results of systematic SARS-CoV-2 testing for asymptomatic patients treated at a tertiary care regional radiation oncology network

BackgroundCoronavirus disease 2019 (COVID-19) caused by the SARS-CoV-2 virus is a current pandemic. We initiated a program of systematic SARS-CoV-2 polymerase chain reaction (PCR) testing in all asymptomatic patients receiving radiotherapy (RT) at a large radiation oncology network in the Charlotte, NC metropolitan region and report adherence and results of the testing program.MethodsPatients undergoing simulation for RT between May 18, 2020 and July 10, 2020 within the Levine Cancer Institute radiation oncology network who were asymptomatic for COVID-19 associated symptoms, without previous positive SARS-CoV-2 testing, and without recent high-risk contacts were included. PCR testing was performed on nasal cavity or nasopharyngeal swab samples. Testing was performed within 2 weeks of RT start (pre-RT) and at least every 4 weeks during RT for patients with prolonged RT courses (intra-RT). An automated task based process using the oncology electronic medical record (EMR) was developed specifically for this purpose.ResultsA total of 604 unique patients were included in the cohort. Details on testing workflow and implementation are described herein. Pre-RT PCR testing was performed in 573 (94.9%) patients, of which 4 (0.7%) were positive. The adherence rate to intra-RT testing overall was 91.6%. Four additional patients (0.7%) tested positive during their RT course, of whom 3 were tested due to symptom development and 1 was asymptomatic and identified via systematic testing. A total of 8 (1.3%) patients tested positive overall. There were no known cases of SARS-CoV-2 transmission from infected patients to clinic staff and/or other patients.ConclusionsWe detailed the workflows used to implement systematic SARS-CoV-2 for asymptomatic patients at a large radiation oncology network. Adherence rates for pre-RT and intra-RT testing were high using this process. This information allowed for appropriate delay in initiating RT, minimizing the occurrence of RT treatment interruptions, and no known cases of transmission from infected patients to clinic staff and/or other patients.

Understanding the drivers of transmission of SARS-CoV-2

Despite the recent development of effective vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), non-pharmaceutical interventions will remain the cornerstone in the battle against COVID-19 for some time. Such interventions are effective but have major societal and economic impacts and should therefore be used as selectively as possible. Quarantine after exposure to a patient with COVID-19 is such a measure. Reported secondary-attack rates among so-called high-risk contacts have varied widely from lower than 1% to 54·9%.

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.

Descriptive epidemiology of SARS-CoV-2 infection in Karnataka state, South India: Transmission dynamics of symptomatic vs. asymptomatic infections.

BackgroundThe huge surge in COVID-19 cases in Karnataka state, India, during early phase of the pandemic especially following return of residents from other states and countries required investigation with respect to transmission dynamics, clinical status, demographics, comorbidities and mortality. Knowledge on the role of symptomatic and asymptomatic cases in transmission of SARS-CoV-2 was not available.MethodsThe study included all the cases reported from March 8 - May 31, 2020. Individuals with a history of international or domestic travel from high burden states, Influenza-like Illness or Severe Acute Respiratory Illness and high-risk contacts of COVID-19 cases were included. Detailed analysis based on contact tracing data available from the line-list of state surveillance unit was performed using cluster network analysis software.FindingsAmongst the 3404 COVID-19 positive cases, 3096 (91%) were asymptomatic while 308 (9%) were symptomatic. Majority of asymptomatic cases were in the age range of 16 and 45 years while symptomatic cases were between 31 and 65 years. Mortality rate was especially higher among middle-aged and elderly cases with co-morbidities, 34/38 (89·4%). Cluster network analysis of 822 cases indicated that the secondary attack rate, size of the cluster and superspreading events were higher when the source case was symptomatic as compared to an asymptomatic.InterpretationOur findings indicate that both asymptomatic and symptomatic SARS-CoV-2 cases transmit the infection, although symptomatic cases were the main driving force within the state during the beginning of the pandemic. Considering the large proportion of asymptomatic cases, their ability to spread infection cannot be overlooked. Notwithstanding the limitations and bias in identifying asymptomatic cases, the findings have major implications for testing policies. Active search, early testing and treatment of symptomatic elderly patients with comorbidities should be prioritized for containing the spread of COVID-19 and reducing mortality.FundingIntermediate Fellowship, Wellcome Trust-DBT India Alliance to Giridhara R Babu, Grant number: IA/CPHI/14/1/501499.

Surveillance of SARS-CoV-2 transmission in educational institutions, August to December 2020, Germany.

This study aims at providing estimates on the transmission risk of SARS-CoV-2 in schools and day-care centres. We calculated secondary attack rates (SARs) using individual-level data from state-wide mandatory notification of index cases in educational institutions, followed by contact tracing and PCR-testing of high-risk contacts. From August to December 2020, every sixth of overall 784 independent index cases was associated with secondary cases in educational institutions. Monitoring of 14 594 institutional high-risk contacts (89% PCR-tested) of 441 index cases during quarantine revealed 196 secondary cases (SAR 1.34%, 0.99-1.78). SARS-CoV-2 infection among high-risk contacts was more likely around teacher-indexes compared to student-/child-indexes (incidence rate ratio (IRR) 3.17, 1.79-5.59), and in day-care centres compared to secondary schools (IRR 3.23, 1.76-5.91), mainly due to clusters around teacher-indexes in day-care containing a higher mean number of secondary cases per index case (142/113 = 1.26) than clusters around student-indexes in schools (82/474 = 0.17). In 2020, SARS-CoV-2 transmission risk in educational settings was low overall, but varied strongly between setting and role of the index case, indicating the chance for targeted intervention. Surveillance of SARS-CoV-2 transmission in educational institutions can powerfully inform public health policy and improve educational justice during the pandemic.

COVID-19 Transmission in Educational Institutions August to December 2020, Rhineland-Palatinate, Germany: A Study of Index Cases and Close Contact Cohorts

Background: The lack of precise estimates on transmission risk hampers rational decisions on closure of educational institutions during the COVID-19 pandemic. Methods: Secondary attack rates (SARs) for schools and day-care centres were calculated using data from state-wide mandatory notification of SARS-CoV-2 index cases in educational institutions and additional information on routine contact tracing and PCR-testing. Findings: From August to December 2020, every sixth of overall 784 reported index cases caused a transmission in educational institutions (risk 0·17, 95% CI 0·14–0·19). In a subgroup, monitoring of 14,594 institutional high-risk contacts (89% PCR-tested) of 441 index cases revealed 196 secondary cases (SAR 1·34%, 1·16–1·54). Transmission was more likely from teachers than from students/children (incidence risk ratio [IRR] 3·17, 1·79–5·59), and from index cases in day-care centres (IRR 3·23, 1·76–5·91) than from those in secondary schools. In 748 index cases, teachers caused four times more secondary cases than children (1·08 vs. 0·25 secondary cases per index, IRR 4·39, 2·67–7·21). This difference was mainly due to common transmission from teacher index cases to teacher contacts (mean secondary cases 0·56 teacher to teacher vs. 0·04 child to teacher, IRR 13·3, 6·6–26·.7). Interpretation: In educational institutions, the risk of contacts to a confirmed COVID-19 case for infection is one percent, but varies depending on type of institution and index case. Hygiene measures targeting the day-care setting and teacher-to-teacher transmission are priorities in reducing the burden of infection and may promote on-site education during the pandemic. Funding: No particular funding was received for this study.Declaration of Interests: All authors, no conflicts.Ethics Approval Statement: The collection, analysis and communication of the presented data take place in response to the global COVID-19 pandemic and are mandated by the German Infectious Diseases Protection Act. Neither individual informed consent nor approval by an institutional review board are deemed necessary.

Laboratory Diagnosis of SARS Corona Virus-2 Infection: Single Centre Experience of First 12,000 Samples

Introduction: First spotted in Wuhan, China, World Health Organisation declared the deadly outbreak caused by novel Severe Acute Respiratory Syndrome Coronavirus-2 (SARS CoV-2) as global pandemic on March 11, 2020. With over 72 million cases globally till December 2020, countries need to gear up to detect, isolate and treat Corona Virus Disease-2019 (COVID-19) cases. Laboratories play a crucial role in diagnosis thereby instituting early contact tracing and quarantine measures. The laboratory based COVID-19 diagnostic testing data may help in formulating strategies to contain the spread of infection. Aim: To describe key patient variables of the respiratory samples processed for SARS-CoV-2 by Real Time Polymerase Chain Reaction (RT-PCR) at a diagnostic laboratory. Materials and Methods: In this descriptive, single centre study carried out at ICMR approved COVID-19 diagnostic laboratory, nasopharyngeal swabs received in Viral Transport Medium (VTM) were tested for SARS-CoV-2 infection by RT-PCR. Key patient variables, like age, gender, symptoms and sample positivity rate were tabulated. The demographic and clinical data of samples tested were summarised by medians and Interquartile Range (IQR) for continuous variables and by proportions for categorical variables. Results: A total of 12,187 samples were received between 21st March to 8th July 2020. The data from 11,196 individuals were complete and were included in the analysis. Overall, 2,053 samples were tested positive for SARS-CoV-2 indicating positivity rate of 18.33%. Sample positivity was highest (63.91%) among high-risk contacts of a laboratory confirmed case. The maximum number of samples tested belonged to age group of 21-40 years and male predominance was observed. Conclusion: Although social distancing, mask usage, hand hygiene and respiratory etiquettes are important measures for containment of COVID-19, strengthening and capacity building of laboratory network is crucial for mitigating the pandemic.

Nonpharmaceutical interventions contribute to the control of COVID-19 in China based on a pairwise model.

Nonpharmaceutical interventions (NPIs), particularly contact tracing isolation and household quarantine, play a vital role in effectively bringing the Coronavirus Disease 2019 (COVID-19) under control in China. The pairwise model, has an inherent advantage in characterizing those two NPIs than the classical well-mixed models. Therefore, in this paper, we devised a pairwise epidemic model with NPIs to analyze COVID-19 outbreak in China by using confirmed cases during February 3rd–22nd, 2020. By explicitly incorporating contact tracing isolation and family clusters caused by household quarantine, our model provided a good fit to the trajectory of COVID-19 infections. We calculated the reproduction number R = 1.345 (95% CI: 1.230 − 1.460) for Hubei province and R = 1.217 (95% CI: 1.207 − 1.227) for China (except Hubei). We also estimated the peak time of infections, the epidemic duration and the final size, which are basically consistent with real observation. We indicated by simulation that the traced high-risk contacts from incubated to susceptible decrease under NPIs, regardless of infected cases. The sensitivity analysis showed that reducing the exposure of the susceptible and increasing the clustering coefficient bolster COVID-19 control. With the enforcement of household quarantine, the reproduction number R and the epidemic prevalence declined effectively. Furthermore, we obtained the resumption time of work and production in China (except Hubei) on 10th March and in Hubei at the end of April 2020, respectively, which is broadly in line with the actual time. Our results may provide some potential lessons from China on the control of COVID-19 for other parts of the world.

A Correlation of Kidney Changes and Sars Cov 2 in Covid Positive Patients –A Review Article

COVID-19, a respiratory illness caused by a newly discovered coronavirus, has become a pandemic affecting over 1.9 million people with over 130,000 deaths in 210 countries.Some people become infected with the virus but do not develop symptoms. When they appear, symptoms are non-specific, with fever, cough, shortness of breath, sore throat, fatigue, and headache being the most common. Symptoms are usually mild and benign in a vast majority (&gt;80%) and recede gradually, leading to a full spontaneous recovery. A small number become seriously ill, develop difficulty in breathing and complications related to other organs. They may require hospitalization and a smaller subset need ICU care. The mortality is relatively higher in the latter group. This risk goes up in the elderly and those with co-orbidities (such ashypertension, diabetes, cardiac disease, kidney failure). Still, it is essential to emphasize that everybody is at risk for severe disease (including the relatively young and healthy dialysis staff). The strategy of physical distancing, case finding, contact tracing and quarantine/isolation of positive cases and high-risk contacts is critical to controlling the spread of this infection. This strategy is being implemented through nationwide lockdown during the period of intense transmission. Still, physical distancing is likely to remain in force after the end of the current lockdown to prevent disease spread.

451. Evaluation of Exposure History in Healthcare Personnel with Coronavirus 2019 Disease

BackgroundDuring the Coronavirus Disease 2019 (COVID-19) pandemic, many healthcare personnel (HCP) have developed COVID-19. However, there is uncertainty regarding whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was acquired at work versus in the community.MethodsWe conducted a cohort study to examine exposure history of personnel with COVID-19 infection or asymptomatic carriage in a VA healthcare system. High-risk exposures were classified based Centers for Disease Control and Prevention criteria.ResultsOf 578 personnel tested, 49 (8%) had nasopharyngeal swabs with positive PCR results, including 45 (92%) with and 4 (8%) without COVID-19 symptoms. Of the 49 cases, 21 (43%) had a documented high-risk exposure at work, including 14 exposures to COVID-19 patients and 7 exposures to colonized or infected personnel. Exposures to infected patients most often were a result of delays in recognition of COVID-19 due to atypical presentations. Exposures to personnel with COVID-19 most often involved activities such as meals when facemasks were not worn. Most cases occurred among nurses (26, 53%) and administrative personnel (10, 20%); only 3 physicians developed COVID-19. No cases occurred in personnel working on COVID-19 wards. All personnel had mild or moderate disease.ConclusionForty-three percent of healthcare personnel with COVID-19 had prior high-risk exposures at work. Improved detection of patients with atypical presentations and efforts to reduce high-risk contacts among personnel may reduce the risk for acquisition of SARS-CoV-2.Disclosures All Authors: No reported disclosures

Limited Secondary Transmission of the Novel Coronavirus (SARS-CoV-2) by Asymptomatic and Mild COVID-19 Patients in Bhutan.

.As the COVID-19 pandemic continues, there is growing concordance and persisting conflicts on the virus and the disease process. We discuss limited transmissibility of the virus by asymptomatic and mild cases of COVID-19 patients in Bhutan. We followed up the secondary transmission of SARS-CoV-2 in the contacts of asymptomatic and mild COVID-19 patients in Bhutan. Bhutan had 33 confirmed COVID-19 cases in the country as of May 29, 2020. Of these, 22 (67%) were females. Except the first two cases (American tourists), the rest were Bhutanese living outside the country. The mean age of the Bhutanese patients was 26.3 (range 16–33) years. Close contacts of 27 of the 33 cases were followed up for signs and symptoms and COVID-19 positivity. The first two cases had 73 and 97 primary contacts, respectively, and equal number of secondary contacts (224). From the third case, a mandatory 21-day facility quarantine was instituted, all primary contacts were facility quarantined, and there were no secondary contacts. In total, the 27 cases had 1,095 primary contacts and 448 secondary contacts. Of these, 75 individuals were categorized as definite high-risk contacts. Secondary transmission occurred in seven high-risk contacts. Therefore, the overall secondary transmission was 9.0% (7/75) and 0.6% (7/1,095) among the high-risk and primary contacts, respectively. No transmission occurred in the secondary contacts. In contrast to several reports indicating high transmissibility of SARS-CoV-2 in contacts of confirmed cases, the mostly young, asymptomatic, and mild cases of COVID-19 in Bhutan showed limited secondary transmission.

Risk Stratification as a Tool to Rationalize Quarantine of Health Care Workers Exposed to COVID-19 Cases: Evidence From a Tertiary Health Care Center in India.

Quarantine of health care workers (HCWs) exposed to COVID-19-confirmed cases is a well-known strategy for limiting the transmission of infection. However, during a pandemic situation in a resource-constraint setting, we require an evidence-based guideline for quarantining HCWs. We developed an algorithm for exposure-based risk stratification and quarantine of HCWs. We did contact tracing and risk stratification of 3853 HCWs, of whom 560 (14.5%) were categorized as high-risk contacts. High-risk contacts were quarantined for 14 days and underwent testing for COVID-19, while low-risk contacts continued their work with adherence to physical distancing, hand hygiene, appropriate use of personal protective equipment, and self-monitoring of symptoms. Overall, 118 (3.1%) contacts tested positive for COVID-19. The positivity rate among high-risk contacts was 7.1% (95% confidence interval = 5.2-9.6). Our strategy of risk stratification prevented 3215 HCWs from being quarantined and thus saved 45 010 person-days of health workforce in the institution.

SARS-CoV-2 seroprevalence and transmission risk factors among high-risk close contacts: a retrospective cohort study

BackgroundThe proportion of asymptomatic carriers and transmission risk factors of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among household and non-household contacts remains unclear. In Singapore, extensive contact tracing by the Ministry of Health for every diagnosed COVID-19 case, and legally enforced quarantine and intensive health surveillance of close contacts provided a rare opportunity to determine asymptomatic attack rates and SARS-CoV-2 transmission risk factors among community close contacts of patients with COVID-19.MethodsThis retrospective cohort study involved all close contacts of confirmed COVID-19 cases in Singapore, identified between Jan 23 and April 3, 2020. Household contacts were defined as individuals who shared a residence with the index COVID-19 case. Non-household close contacts were defined as those who had contact for at least 30 min within 2 m of the index case. All patients with COVID-19 in Singapore received inpatient treatment, with access restricted to health-care staff. All close contacts were quarantined for 14 days with thrice-daily symptom monitoring via telephone. Symptomatic contacts underwent PCR testing for SARS-CoV-2. Secondary clinical attack rates were derived from the prevalence of PCR-confirmed SARS-CoV-2 among close contacts. Consenting contacts underwent serology testing and detailed exposure risk assessment. Bayesian modelling was used to estimate the prevalence of missed diagnoses and asymptomatic SARS-CoV-2-positive cases. Univariable and multivariable logistic regression models were used to determine SARS-CoV-2 transmission risk factors.FindingsBetween Jan 23 and April 3, 2020, 7770 close contacts (1863 household contacts, 2319 work contacts, and 3588 social contacts) linked to 1114 PCR-confirmed index cases were identified. Symptom-based PCR testing detected 188 COVID-19 cases, and 7582 close contacts completed quarantine without a positive SARS-CoV-2 PCR test. Among 7518 (96·8%) of the 7770 close contacts with complete data, the secondary clinical attack rate was 5·9% (95% CI 4·9–7·1) for 1779 household contacts, 1·3% (0·9–1·9) for 2231 work contacts, and 1·3% (1·0–1·7) for 3508 social contacts. Bayesian analysis of serology and symptom data obtained from 1150 close contacts (524 household contacts, 207 work contacts, and 419 social contacts) estimated that a symptom-based PCR-testing strategy missed 62% (95% credible interval 55–69) of COVID-19 diagnoses, and 36% (27–45) of individuals with SARS-CoV-2 infection were asymptomatic. Sharing a bedroom (multivariable odds ratio [OR] 5·38 [95% CI 1·82–15·84]; p=0·0023) and being spoken to by an index case for 30 min or longer (7·86 [3·86–16·02]; p<0·0001) were associated with SARS-CoV-2 transmission among household contacts. Among non-household contacts, exposure to more than one case (multivariable OR 3·92 [95% CI 2·07–7·40], p<0·0001), being spoken to by an index case for 30 min or longer (2·67 [1·21–5·88]; p=0·015), and sharing a vehicle with an index case (3·07 [1·55–6·08]; p=0·0013) were associated with SARS-CoV-2 transmission. Among both household and non-household contacts, indirect contact, meal sharing, and lavatory co-usage were not independently associated with SARS-CoV-2 transmission.InterpretationTargeted community measures should include physical distancing and minimising verbal interactions. Testing of all household contacts, including asymptomatic individuals, is warranted.FundingMinistry of Health of Singapore, National Research Foundation of Singapore, and National Natural Science Foundation of China.

Can Tracking Data Help in Assessing Interpersonal Contact Exposure in Team Sports during the COVID-19 Pandemic?

During the COVID-19 pandemic, the temporary closure of physical activity and sports facilities, and the generalized cancellation or postponement of sports events have a massive impact on social and economic development. In this study, we explored the feasibility of using tracking data from a football match to assess interpersonal contact between individuals by calculating two measures of respiratory exposure. The dynamic tracking positioning of all players and referees during one international football match was analyzed. For each individual, two measures of respiratory exposure were calculated, based on the 2 m interpersonal distance recommendations for contact tracing for COVID-19 control. Overall, individuals spent a median of 0:12 mm:ss (IQR = 0:45 mm:ss) exposed to interpersonal contact of fewer than 2 m from others. The highest value of exposure was observed between two players of opposing teams (6:35 mm:ss). The results suggest that tracking data can be used to assess respiratory exposure to interpersonal contact in team sports, such as football. The measures of exposure calculated can be used to the prompt identification of high-risk contacts of COVID-19 cases during a match or a training session, but also the risk stratification of different sports and physical activities.

Control of a Nosocomial Outbreak of COVID-19 in a University Hospital.

BackgroundNosocomial spread of coronavirus disease 2019 (COVID-19) causes clusters of infection among high-risk individuals. Controlling this spread is critical to reducing COVID-19 morbidity and mortality. We describe an outbreak of COVID-19 in Keio University Hospital, Japan, and its control and propose effective control measures.MethodsWhen an outbreak was suspected, immediate isolation and thorough polymerase chain reaction (PCR) testing of patients and health care workers (HCWs) using an in-house system, together with extensive contact tracing and social distancing measures, were conducted. Nosocomial infections (NIs) were defined as having an onset or positive test after the fifth day of admission for patients and having high-risk contacts in our hospital for HCWs. We performed descriptive analyses for this outbreak.ResultsBetween March 24 and April 24, 2020, 27 of 562 tested patients were confirmed positive, of whom 5 (18.5%) were suspected as NIs. For HCWs, 52 of 697 tested positive, and 40 (76.9%) were considered NIs. Among transmissions, 95.5% were suspected of having occurred during the asymptomatic period. Large-scale isolation and testing at the first sign of outbreak terminated NIs. The number of secondary cases directly generated by a single primary case found before March 31 was 1.74, compared with 0 after April 1. Only 4 of 28 primary cases generated definite secondary infection; these were all asymptomatic.ConclusionsViral shedding from asymptomatic cases played a major role in NIs. PCR screening of asymptomatic individuals helped clarify the pattern of spread. Immediate large-scale isolation, contact tracing, and social distancing measures were essential to containing outbreaks.