High-risk Contacts Research Articles

Opportunities and lessons learned from a retrospective analysis of administrative billing data to understand the language profile of high-risk close contacts of COVID-19 cases in Ontario.

During a public health emergency, it is vital to have access to data sources that can identify communities disproportionately affected and to ensure public health communications are meeting the needs of diverse populations. To explore how administrative billing data for language interpretation services could be used as an additional source of information to understand the language profile of high-risk close contacts of COVID-19 cases. A retrospective descriptive analysis was conducted using administrative billing data from Public Health Ontario's Contact Tracing Initiative from May 2020 to February 2022. Data from the Contact Tracing Initiative were utilized to identify drivers that could have influenced patterns in language interpretation requests. Trends were compared with community language profiles using 2021 Canadian Census data. Interpreters responded to 2,604 requests across 38,518 interpretation minutes and provided information in 50 different languages. The top five requested languages were French, Arabic, Spanish, Punjabi and Mandarin. Five distinct periods were identified of different language predominance including Spanish in spring/summer 2020, French in summer/fall 2020 and Arabic in spring 2021. Overall, these trends aligned with the language profile of health units contributing most submissions. Public health agencies could benefit from using existing secondary data sources to understand the language interpretation needs of their communities. This study also demonstrated how existing data sources could be used to help assess how communities are being disproportionately affected by public health emergencies and how this might change over time.

Personal characteristics and transmission dynamics associated with SARS-CoV-2 semi-quantitative PCR test results: an observational study from Belgium, 2021-2022.

Following harmonization efforts by the Belgian National Reference Center for SARS-CoV-2, semi-quantitative PCR test (SQ-PCR) results, used as a proxy for viral load, were routinely collected after performing RT-qPCR tests. We investigated both the personal characteristics associated with SQ-PCR results and the transmission dynamics involving these results. We used person-level laboratory test data and contact tracing data collected in Belgium from March 2021 to February 2022. Personal characteristics (age, sex, vaccination, and laboratory-confirmed prior infection) and disease stage by date of symptom onset were analyzed in relation to SQ-PCR results using logistic regression. Vaccine effectiveness (VE) against a high viral load (≥107 copies/mL) was estimated from the adjusted probabilities. Contact tracing involves the mandatory testing of high-risk exposure contacts (HREC) after contact with an index case. Odds ratios for test positivity and high viral load in HREC were calculated based on the SQ-PCR result of the index case using logistic regression models adjusted for age, sex, immunity status (vaccination, laboratory-confirmed prior infection), variant (Alpha, Delta, Omicron), calendar time, and contact tracing covariates. We included 909,157 SQ-PCR results of COVID-19 cases, 379,640 PCR results from index cases, and 72,052 SQ-PCR results of HREC. High viral load was observed more frequently among recent cases, symptomatic cases, cases over 25 years of age, and those not recently vaccinated (>90 days). The vaccine effectiveness (VE) of the primary schedule in the first 30 days after vaccination was estimated at 47.3% (95%CI 40.8-53.2) during the Delta variant period. A high viral load in index cases was associated with an increased test positivity in HREC (OR 2.7, 95%CI 2.62-2.79) and, among those testing positive, an increased likelihood of a high viral load (OR 2.84, 95%CI 2.53-3.19).

Use of Antigen Rapid Diagnostic Test for Detection of COVID-19 Cases in University Settings in Cameroon.

Robust testing strategies are an essential aspect of COVID-19 pandemic preparedness and response. In 2022, most regions of Cameroon were still below the WHO's recommended level of 10 COVID-19 tests per 10,000 population. This study aimed to detect SARS-CoV-2 cases in university settings in Cameroon using antigen rapid diagnostic tests (Ag-RDTs) to increase national testing capacity and assess the knowledge, attitudes, and practices of this population regarding COVID-19 infection. Six universities in Buea, Douala, Dschang, Maroua, Ngaoundere, and Yaounde participated in this study from June to October 2022. Nasopharyngeal swabs were collected from participants and tested for COVID-19 using Ag-RDTs. For all positive cases, high-risk contacts were also tested by Ag-RDT. Participants were administered a structured questionnaire to assess their knowledge, attitudes, and practices regarding COVID-19. A total of 7,006 participants were recruited, and 54 (0.8%) were positive for SARS-CoV-2. Among close contacts, three of 62 (4.8%) tested positive. The University of Maroua was the only site to consistently report satisfactory testing capacity, achieving the study target of 30 tests/10,000 in 94.1% of cases. Participants' knowledge of COVID-19 was moderate to good (≥50%). However, 28% were unsure about the effectiveness of the COVID-19 vaccine. Two main factors were identified that could facilitate the spread of SARS-CoV-2 in university settings, namely the lack of restrictions on entering campus without a mask (36%) and the non-respect of social distancing on campus (42.7%). The results of this study will guide future policies to better control diseases with epidemic or pandemic potential by targeting educational institutions.

Contacts with health services for COVID-19-related reasons during the first wave of the pandemic in Portugal: a longitudinal study

IntroductionAccess to COVID-19-related care during the pandemic deserve attention and study to inform future strategies to deal with similar health emergencies in the future. We aimed to describe access to...

Evaluating the Usefulness of Population-Wide COVID-19 Testing in the Omicron Era: Insights from a German Model.

The Omicron variant of SARS-CoV-2, which has become dominant worldwide since late 2021, presents a unique challenge due to its high rate of asymptomatic transmission. This study evaluates the efficacy and value of population-wide testing, including self-testing, in the context of COVID-19, particularly under the Omicron variant, using data from Germany. A decision-analytical model and secondary data was used for assessing the impact of systematic screening and testing for COVID-19. Various scenarios were taken into consideration including seasonal patterns of COVID-19 transmission and the potential for annual waves. The model assessed the clinical benefits of testing against the backdrop of vaccine effectiveness, transmission rates, and the potential to prevent severe clinical events, including death, ICU admission, and long COVID syndrome. The study found that the value of mass testing and self-testing for private use was highly contingent on the transmission rate and the scenario of COVID-19 waves (seasonal vs. continuous). For winter waves, a very high incidence rate was required to justify testing, while for continuous waves, testing could be valuable for those in contact with individuals in their last decade of life. The analysis highlighted the limitations of mass testing when community transmission rates were low and the potential value of testing in high-risk contacts or amidst new outbreaks. The findings suggest that the resumption of testing during winter waves is unlikely to provide significant clinical benefits given the current understanding of Omicron's transmission and immunity waning. This study underscores the need for a nuanced approach to COVID-19 testing policies, considering both the epidemiological context and the practical implications of testing strategies.

Nitric oxide brings innate immune resistance to M. tuberculosis infection among high-risk household contacts of pulmonary tuberculosis patients

Nitric oxide brings innate immune resistance to M. tuberculosis infection among high-risk household contacts of pulmonary tuberculosis patients

Evaluating the Experience of Teen-to-Teen Crisis Line Volunteers: A Pilot Study.

Teen-to-teen (t2t) crisis lines are a special type of crisis service where youth volunteers help their peers. Although prior research has examined the experience of adult crisis line responders, no research has examined the experience of adolescents who do this work. In collaboration with two of the largest t2t lines in the U.S., this pilot study is the first examination of t2t crisis line work. Volunteers (ages 14-20) reported: their primary motivation for joining the crisis lines was to help others and give back to the community; responding to a range of peers' problems on the t2t crisis line, including high-risk suicide contacts; and a range of ways the crisis line work impacted their lives. Findings provide preliminary information about the experience of adolescents engaging in t2t crisis line work. Additional research is needed in larger and more diverse samples to understand the impact of crisis line work for youth.

Analysis of the effectiveness of hygiene measures and COVID-19 vaccination at a tertiary-care university hospital during the first two years of the SARS-CoV-2 pandemic

ObjectiveAssessment of the effectiveness of protective measures at a tertiary-care hospital during the SARS-CoV-2 infection waves to provide advice for future pandemics. DesignRetrospective cohort study among hospital staff using in-house surveillance data. SettingUniversity Hospital Erlangen (UKER), a tertiary-care provider in Bavaria, Germany. MethodsWe outline the preventive measures introduced at UKER and retrospectively assess their effectiveness using anonymized monitoring data that were collected during the SARS-CoV-2 pandemic from February 2020 to the end of January 2022. Analysed data includes the incidence of SARS-CoV-2 infections among employees, the frequency of high-risk contacts with infected patients or staff members and breakthrough infections considering the context of exposure. ResultsThe cumulative incidence of SARS-CoV-2 infections among UKER employees was higher before, but lower after the vaccination campaign when compared to the general population. Healthcare workers (HCW), notably physicians and nurses, were especially at risk of infection compared to other UKER employees with less direct patient contact (OR 1.36 [95% CI 1.18-1.57 p < 0.001]). Breakthrough infections mostly occurred after exposure during private life, i.e. in situations without protective equipment. The frequency of high-risk contacts during direct patient care remained stable after SARS-CoV-2 vaccination. Prior to vaccination, 5.2% of HCW with direct patient care tested positive for SARS-CoV-2 within 14 days. After vaccination until the onset of the Omicron wave, conversion rate dropped to 0%. ConclusionsThis study provides real-world data on the effectiveness of vaccination, contact tracing, personal protective equipment and general hygiene measures during the SARS-CoV-2 pandemic. Based on our findings, we recommend a protective approach combining all these preventive measures.

Systems analysis and improvement approach to optimize tuberculosis (SAIA-TB) screening, treatment, and prevention in South Africa: a stepped-wedge cluster randomized trial

BackgroundThe use of systems engineering tools, including the development and use of care cascades using routinely collected data, process mapping, and continuous quality improvement, is used for frontline healthcare workers to devise systems level change. South Africa experiences high rates of tuberculosis (TB) infection and disease as well as HIV co-infection. The Department of Health has made significant gains in HIV services over the last two decades, reaching their set “90–90-90” targets for HIV. However, TB services, although robust, have lagged in comparison for both disease and infection. The Systems Analysis and Improvement Approach (SAIA) is a five-step implementation science method, drawn from systems engineering, to identify, define, and implement workflow modifications using cascade analysis, process mapping, and repeated quality improvement cycles within healthcare facilities.MethodsThis stepped-wedge cluster randomized trial will evaluate the effectiveness of SAIA on TB (SAIA-TB) cascade optimization for patients with TB and high-risk contacts across 16 clinics in four local municipalities in the Sarah Baartman district, Eastern Cape, South Africa. We hypothesize that SAIA-TB implementation will lead to a 20% increase in each of: TB screening, TB preventive treatment initiation, and TB disease treatment initiation during the 18-month intervention period. Focus group discussions and key informant interviews with clinic staff will also be conducted to determine drivers of implementation variability across clinics.DiscussionThis study has the potential to improve TB screening, treatment initiation, and completion for both active disease and preventive measures among individuals with and without HIV in a high burden setting. SAIA-TB provides frontline health care workers with a systems-level view of their care delivery system with the aim of sustainable systems-level improvements.Trial registrationClinicaltrials.gov, NCT06314386. Registered 18 March 2024, https://clinicaltrials.gov/study/NCT06314386. NCT06314386.

Drug-resistant tuberculosis: a persistent global health concern.

Drug-resistant tuberculosis (TB) is estimated to cause 13% of all antimicrobial resistance-attributable deaths worldwide and is driven by both ongoing resistance acquisition and person-to-person transmission. Poor outcomes are exacerbated by late diagnosis and inadequate access to effective treatment. Advances in rapid molecular testing have recently improved the diagnosis of TB and drug resistance. Next-generation sequencing of Mycobacterium tuberculosis has increased our understanding of genetic resistance mechanisms and can now detect mutations associated with resistance phenotypes. All-oral, shorter drug regimens that can achieve high cure rates of drug-resistant TB within 6-9 months are now available and recommended but have yet to be scaled to global clinical use. Promising regimens for the prevention of drug-resistant TB among high-risk contacts are supported by early clinical trial data but final results are pending. A person-centred approach is crucial in managing drug-resistant TB to reduce the risk of poor treatment outcomes, side effects, stigma and mental health burden associated with the diagnosis. In this Review, we describe current surveillance of drug-resistant TB and the causes, risk factors and determinants of drug resistance as well as the stigma and mental health considerations associated with it. We discuss recent advances in diagnostics and drug-susceptibility testing and outline the progress in developing better treatment and preventive therapies.

Epidemiology, clinical presentation, and outcome of mpox: A study of 381 cases in Saudi Arabia

ObjectivesThere are limited data on the clinical and epidemiological aspects of mpox in Saudi Arabia. This study investigates the characteristics of Mpox cases from May to September 2023. MethodsA total of 381 cases of Mpox were included in this study, diagnosed based on a combination of clinical symptoms and laboratory testing. ResultsThe majority of mpox cases were males (91.1%), with a mean age of (±SD) of 32.4 (±8.3) years; 356 (93.4%) did not report travel, 277 (72.7%) denied engaging in extra-marital sex, and 379 (99.5%) were not linked to secondary cases. Fever was reported in 371 (97.4%), whereas headache was present in 314 (82.4%). Cough (1.3%) and conjunctivitis (0.5%) were rare. The most commonly affected areas in terms of lesions were the palms and soles (297 cases, 78%), followed by the genitals (206 cases, 54%), face (198 cases, 52%), and mouth (160 cases, 42%). Of the 1325 identified contacts, 1134 (85.5%) were hospital contacts, and 191 (14.5%) were community contacts, and 393 (29.6%) were high-risk contact. Of the high-risk contacts, 284 (72.3%) accepted post-exposure vaccination. The genotyped samples were all subclade IIb (formerly the West Africa clade). ConclusionsThis study provides valuable insights into mpox characteristics in Saudi Arabia. The genome of monkeypox virus belonged to subclade IIb of the West Africa clade. Further analysis of the global tree sublineage is needed.

DP-ACT: Decentralized Privacy-Preserving Asymmetric Digital Contact Tracing

Digital contact tracing substantially improves the identification of high-risk contacts during pandemics. Despite several attempts to encourage people to use digital contact-tracing applications by developing and rolling out decentralized privacy-preserving protocols (broadcasting pseudo-random IDs over Bluetooth Low Energy---BLE), the adoption of digital contact tracing mobile applications has been limited, with privacy being one of the main concerns. In this paper, we propose a decentralized privacy-preserving contact tracing protocol, called DP-ACT, with both active and passive participants. Active participants broadcast BLE beacons with pseudo-random IDs, while passive participants model conservative users who do not broadcast BLE beacons but still listen to the broadcasted BLE beacons. We analyze the proposed protocol and discuss a set of interesting properties. The proposed protocol is evaluated using both a face-to-face individual interaction dataset and five real-world BLE datasets. Our simulation results demonstrate that the proposed DP-ACT protocol outperforms the state-of-the-art protocols in the presence of passive users.

Effectiveness of contact tracing for COVID-19 in Belgium

Contact tracing and investigation can prevent infectious disease transmission when carried out promptly. Data obtained from contact tracing also provides unique information on transmission dynamics that can be useful for policy making. The proportion of secondary infections arising from index cases that were previously identified as a close contact, hence “known index cases”, has been indicated by ECDC as a key performance indicator for contact tracing. Few empirical studies have been published on the effectiveness of contact tracing and investigation during the COVID-19 pandemic.&#x0D; Using data from the Belgian COVID-19 contact tracing (Sept 2020 – Dec 2021), we investigated the impact of contact tracing on onward transmission. Known index cases were compared to those not previously identified as close contact. More specifically, we compared their traced contacts and secondary cases as well as the serial interval, representing the time from illness onset in the primary case to illness onset in the secondary case. In addition, we investigated contact and transmission characteristics by age.&#x0D; Known index cases, previously informed about their exposure, were linked to fewer high-risk contacts and secondary infections. In addition, they presented a lower secondary attack rate compared to those not previously identified by contact investigation, suggesting behavioural changes. Also, a shorter serial interval was observed for known index cases. In addition to breaking transmission chains, contact tracing provides important information on transmission characteristics. When exploring age-specific data, we observed increased transmission rates from children to adults during the circulation of Delta and Omicron variants without an increase in contact rates between these age groups.&#x0D; The lower secondary attack rates for known index cases suggest that contact tracing in Belgium has been effective in reducing onward transmission. Their lower number of traced contacts and shorter serial interval are indicative that individuals aware of their exposure to SARS-CoV-2 were more reserved in their social contact behaviour. This reflects the mandatory quarantine for high-risk contacts. Our study also shows that in times of high burden on the healthcare system, key performance indicators of contact tracing should be interpreted with caution in light of changing intervention strategies. Many external factors influence the effectiveness of contact tracing like testing policy and compliance, the cooperation of index cases, and the imposed and adopted quarantine and isolation policies.&#x0D;

COVID-19 contact tracing at work in Belgium - how tracers tweak guidelines for the better

BackgroundWhen conducting COVID-19 contact tracing, pre-defined criteria allow differentiating high-risk contacts (HRC) from low-risk contacts (LRC). Our study aimed to evaluate whether contact tracers in Belgium followed these criteria in practice and whether their deviations improved the infection risk assessment.MethodWe conducted a retrospective cohort study in Belgium, through an anonymous online survey, sent to 111,763 workers by email. First, we evaluated the concordance between the guideline-based classification of HRC or LRC and the tracer’s classification. We computed positive and negative agreements between both. Second, we used a multivariate Poisson regression to calculate the risk ratio (RR) of testing positive depending on the risk classification by the contact tracer and by the guideline-based risk classification.ResultsFor our first research question, we included 1105 participants. The positive agreement between the guideline-based classification in HRC or LRC and the tracer’s classification was 0.53 (95% CI 0.49–0.57) and the negative agreement 0.70 (95% CI: 0.67–0.72). The type of contact tracer (occupational doctors, internal tracer, general practitioner, other) did not significantly influence the results. For the second research question, we included 589 participants. The RR of testing positive after an HRC compared to an LRC was 3.10 (95% CI: 2.71–3.56) when classified by the contact tracer and 2.24 (95% CI: 1.94–2.60) when classified by the guideline-based criteria.ConclusionOur study indicates that contact tracers did not apply pre-defined criteria for classifying high and low risk contacts. Risk stratification by contact tracers predicts who is at risk of infection better than guidelines only. This result indicates that a knowledgeable tracer can target testing better than a general guideline, asking for a debate on how to adapt the guidelines.

Edge-based compartmental modeling for the spread of cholera on random networks: A case study in Somalia

Cholera remains a major public health problem that threatens human health worldwide and its severity is continuing. In this paper, an edge-based model for cholera transmission on random networks is proposed and investigated. The model assumes that two communities share a common water source and includes three transmission routes, namely intra- and inter-community human-to-human transmission as well as water-to-human transmission. Intra-community human-to-human contacts are modeled through a random contact network, while both inter-community and water-to-human transmission are modeled through external nodes that reach each individual in the network to the same extent. The basic reproduction number and the equations of the final epidemic size are obtained. In addition, our study considers the cholera situation in Banadir, which is one of the most severely infected regions in Somalia, during the period (2019-2021). According to the geographical location, two adjacent districts are selected and our model fits well with the real data on the monthly cumulative cholera cases of these two districts during the above-mentioned period. From the perspective of network topology, cutting off high-risk contacts by supervising, isolating, quarantining and closing places with high-degree cholera-infected individuals to reduce degree heterogeneity is an effective measure to control cholera transmission. Our findings might offer some useful insights on cholera control.

Acceptance and timeliness of post-exposure vaccination against mpox in high-risk contacts, Amsterdam, the Netherlands, May–July 2022

BackgroundMay 2022, several countries reported mpox outbreaks among men-who-have-sex-with-men. In the Netherlands, high-risk contacts were offered the third-generation smallpox vaccine as post-exposure-prophylaxis (PEP) within 4 but maximum 14 days after exposure. We investigated their PEP acceptance, timeliness of uptake and development of mpox for the region of the Public Health Service (PHS) Amsterdam. MethodsHigh-risk contacts identified during 20 May–22 July 2022 were included. Contacts were followed-up 21 days after exposure and classified as: no patient (no mpox symptoms or orthopoxvirus PCR-negative) or mpox patient (clinically suspected mpox or orthopoxvirus PCR-positive). We calculated time intervals between date of last exposure and first PHS consultation, PEP administration, and symptom onset. ResultsTwo-hundred-ninety contacts were at high-risk of mpox predominantly due to sexual and/or direct skin-skin contact (212/290, 73 %). First PHS consultation was a median of 5 (IQR 3, 7) days after exposure, at which point 26/290 (9 %) contacts were ineligible for PEP. 84 % (223/264) of contacts eligible for PEP, received PEP within a median of 6 (IQR 3, 8) days after exposure. Of 282 contacts (missing outcome n = 8) 38 (14 %) developed mpox a median of 7 (IQR 5, 12) days after exposure, of whom 50 % (19/38) developed mpox before their first PHS consultation. Among contacts eligible for PEP, 2/38 (5 %) unvaccinated and 16/218 (7 %) vaccinated contact developed mpox. ConclusionsPEP acceptance among contacts of mpox patients was high. However, PEP timeliness was inadequate. Half of contacts received PEP 6 or more days after exposure, and half of contacts who developed mpox had an onset prior to their first PHS consultation. Estimating PEP vaccine effectiveness is problematic due to the timeliness of PEP and the time it takes to generate vaccine-induced immunity. It is important to assess how PEP timeliness may improve and to promote pre-exposure vaccination to control mpox outbreaks.

A network meta-analysis of risk factors of infection among close contacts of COVID-19

ObjectiveWe aimed to use network meta-analysis to compare the impact of infection risk factors of close contacts with COVID-19, identify the most influential factors and rank their subgroups. It can provide a theoretical basis for the rapid and accurate tracking and management of close contacts. MethodsWe searched nine databases from December 1, 2019 to August 2, 2023, which only took Chinese and English studies into consideration. Odd ratios (ORs) were calculated from traditional meta-estimated secondary attack rates (SARs) for different risk factors, and risk ranking of these risk factors was calculated by the surface under the cumulative ranking curve (SUCRA). Results25 studies with 152647 participants identified. Among all risk factors, the SUCRA of type of contact was 69.6 % and ranked first. Among six types of contact, compared with transportation contact, medical contact, social contact and other, daily contact increased risk of infection by 12.11 (OR: 12.11, 95 % confidence interval (CI): 6.51–22.55), 7.76 (OR: 7.76, 95 % CI: 4.09–14.73), 4.65 (OR: 4.65, 95 % CI: 2.66–8.51) and 8.23 OR: 8.23, 95 % CI: 4.23–16.01) times, respectively. Overall, SUCRA ranks from highest to lowest as daily contact (94.7 %), contact with pollution subjects (78.4 %), social contact (60.8 %), medical contact (31.8 %), other (27.9 %), transportation contact (6.4 %). ConclusionThe type of contact had the greatest impact on COVID-19 close contacts infection among the risk factors we included. Daily contact carried the greatest risk of infection among six types of contact, followed by contact with pollution subjects, social contact, other, medical contact and transportation contact. The results can provide scientific basis for rapid assess the risk of infection among close contacts based on fewer risk factors and pay attention to high-risk close contacts during management, thereby reducing tracking and management costs.

Measuring the clustering effect of the SARS-CoV-2 transmission in a school population: a cross-sectional study in a high incidence region

Since the beginning of the pandemic, there has been a great deal of controversy regarding the role of schools in the spread of SARS-CoV-2 infection, and the relative contribution of students, teachers, and others. To quantify the clustering effect of SARS-CoV-2 infection within classes and schools considering the seroprevalence of specific antibodies among students and school staff (teachers and non-teachers) evaluated in schools located in the Northern region of Portugal. 1517 individuals (1307 students and 210 school staff) from 4 public and 2 private schools, comprising daycare to secondary levels, were evaluated. A rapid point-of-care test for SARS-CoV-2 specific IgM and IgG antibodies was performed and a questionnaire was completed providing sociodemographic and clinical information. We calculated the seroprevalence of IgM and IgG antibodies and estimated the Median Odds Ratio (OR) and 95% confidence interval (CI) to assess the clustering effect, using a multilevel (school and class) logistic regression. SARS-CoV-2 seroprevalence (IgM or IgG) was 21.8% and 23.8% (p = 0.575) in students and school staff, respectively. A total of 84 (8.6%) students and 35 (16.7%) school staff reported a previous molecular diagnosis. Among students, those who reported high-risk contacts only at school (OR = 1.13; 95% CI 0.72–1.78) had a seroprevalence similar to those without high-risk contacts; however, seroprevalence was significantly higher among those who only reported a high-risk contact outside the school (OR = 6.56; 95% CI 3.68–11.72), or in both places (OR = 7.83; 95% CI 5.14–11.93). Similar associations were found for school staff. The median OR was 1.00 (95% CI 1.00, 1.38) at the school-level and 1.78 (95% CI 1.40, 2.06) at the class-level. SARS-CoV-2 seroprevalence was similar between students and staff, without a clustering effect observed at the school level, and only a moderate clustering effect documented within classes. These results indicate that the mitigation measures in the school environment can prevent the spread of class outbreaks to the remaining school community.

Exposure to COVID-19 among unvaccinated healthcare personnel and risk for infection: a single-center retrospective study.

Characteristics of exposure and infection risk, are important in strategy development for infection control among healthcare workers (HCWs). Our objective was to investigate the characteristics of exposure of HCWs to SARS-CoV-2 and determine the risk of COVID-19 development. This is a retrospective single-center cohort study, conducted between March and December 2020. Unvaccinated and exposed HCWs were asked to complete a standard form, including demographic data and characteristics of exposure(s). Exposures were stratified according to national guidelines. STROBE checklist was used. Among a total of 4,385 healthcare workers, 1,483 HCWs (33.8%) with a total of 1,903 exposures to SARS-CoV-2 were identified. Median age was 31 (IQR: 26-40) years and 45.4% were male (N = 673). Following exposure, 78 HCWs became SARS-CoV-2-positive (attack rate: 3.9%) and secondary attack rate was 4/16. In terms of infection, exposure to SARS-CoV-2-positive HCWs posed a greater risk compared to contact with patients (8.9%, [n = 66] vs. 3.8% [n = 12], respectively, p = 0.003). PCR positivity rates were 11.5%, 6.3%, and 8.4% for low, medium, and high-risk contacts (p = 0.152). Median time to infection post-exposure was 7 (IQR: 4-13) days. Given the attack rates, there was no correlation between risk levels and PCR test positivity rates. There was no difference between HCWs with or without work restrictions, in terms of PCR positivity. Due to feasibility issues, prioritizing universally applied symptom screening and resource control strategies and suspending contact tracing and work restrictions, appear to be safe during high prevalence period.

Effectiveness and resource utilization of hospital-based contact tracing of patients and health care workers with COVID-19 at a tertiary teaching hospital in Thailand

BackgroundThe benefits of contact tracing in health care workers (HCWs) and patients in hospital have rarely been evaluated. This study aimed to assess the yield of contact tracing in order to evaluate the usefulness of resource utilization. MethodsData were collected from 1 April 2021 to 31 March 2022 at teaching hospital in Thailand. The team was notified if any HCW or patient admitted outside COVID-19 designated areas were tested positive. Those with high-risk exposure identified by the team needed to leave from work for 14 days and 2 PCR tests as early as possible and day 14 after the exposure. ResultA total of 4,292 HCWs and 422 patients were exposed to 575 COVID-19 cases and were identified as high-risk contacts, leading to 50,312 days of quarantine and 9,333 PCR tests. The secondary attack rate was 3.42%, which was more common in patients than in HCWs (OR = 1.82, 95%CI = 1.17–2.85, p = 0.0082). Close contact with patients had more secondary attack rates than with HCWs (OR = 1.51, 95%CI:1.01–2.25, p = 0.045). Among those who had close contact with patients, patients but not HCWs had increased risk of infection (OR = 2.86; 95%CI:1.24–6.62; p = 0.0138, OR = 1.06; 95%CI:0.63–1.77; p = 0.834, respectively). The positivity rate of high-risk close contact HCWs was 2.28 per 1,000 person-days after contact, as compared to the positivity rate of low-risk close contact with symptoms at 0.35 per 1,000 person-days during the same period. ConclusionsHospital-based contact tracing could identify more infected HCWs than symptomatic testing alone. Identifying more infected HCWs could potentially prevent infection in both HCWs and patients.