Contact Tracing: Barriers and Facilitators

Impact of a University-Led COVID-19 Case Investigation and Contact Tracing Program

CONTEXT

The coronavirus disease 2019 (COVID-19) pandemic devastated societies and economies worldwide. Given the major disruptions to higher education, reflection on university responses to the COVID-19 pandemic may provide insights for future outbreaks.

OBJECTIVE

Here, we describe the epidemiology of COVID-19 on the Emory University campus during the 2020-2021 academic year and provide an evaluation of the performance of a university-led program with the purpose of describing the effectiveness of efforts to augment the public health authority's case investigation and contact tracing efforts during a public health emergency.

DESIGN

Evaluation of a case investigation and contact tracing program regarding operations, timeliness, and performance.

MAIN OUTCOME MEASURES

We analyzed quality metrics to determine the proportion of cases and contacts interviewed and the time to completion of each step from case diagnosis to testing of contacts.

RESULTS

During the 2020-2021 academic year, 1267 COVID-19 cases among Emory students, faculty, and staff were confirmed by polymerase chain reaction, with 1132 reported close contacts. Among cases, the median test turnaround time was 1 day (interquartile range: 1, 2). Among both cases and close contacts, 98% were successfully interviewed. The team called a majority of cases on the same day as their test result was reported to the program (87%; n = 1052). Almost all (98%; n = 1247) cases completed isolation or were advised to isolate during the review period. Close to half (46%; n = 513) of contacts interviewed began quarantine before their interview. Among close contacts interviewed, 13% (n = 145) subsequently converted to an index case.

CONCLUSIONS

The impact and performance of Emory's program may provide useful and actionable data for future university-led infectious disease outbreak response programs. The program structure, performance metrics, and information collected via interviews provide practical implications and an organized structure to guide other programs during future outbreaks.

Barriers and Facilitators Affecting Access to Health Care for People With Syphilis: Protocol for a Scoping Review

BACKGROUND

Syphilis is a systemic, preventable, and curable infection caused by the bacterium Treponema pallidum. Despite being treatable, syphilis continues to have a high incidence, with a resurgence observed even in countries with strong health surveillance systems. This highlights the need to understand the various strategies used globally to improve access to care for individuals with syphilis.

OBJECTIVE

This scoping review aims to identify and map the barriers and facilitators affecting access to health care for people with syphilis.

METHODS

This scoping review will follow the methodology outlined by the Joanna Briggs Institute. The search will be conducted across several databases, including PubMed/MEDLINE, Scopus, Embase, LILACS (Virtual Health Library), and CINAHL (EBSCO). In addition, sources of unpublished studies or gray literature will be explored. Studies focusing on access to health care for individuals with syphilis will be included, regardless of geographic location, country, or language. Two independent reviewers will assess the results, and data will be extracted using a tool specifically developed for this review. The extracted quantitative data will be presented in tables and analyzed using descending hierarchical classification, represented by a class dendrogram. Barriers and facilitators will be categorized into dimensions of access.

RESULTS

Database searching began in October 2024. Full-text screening and review are expected to be completed in December 2024. Data extraction and analysis are expected to be completed by February 2025, and the final report will be completed in March 2025.

CONCLUSIONS

The findings of this scoping review, guided by this protocol, will elucidate the main barriers and facilitators that affect access to syphilis treatment. This study may contribute to the practices of health professionals, managers, and the academic community, and provide relevant information for the population.

TRIAL REGISTRATION

Open Science Framework Registries osf.io/kpsab; https://osf.io/kpsab.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/63561.

Mpox in UK households: estimating secondary attack rates and factors associated with transmission, May-November 2022

We aimed to estimate the secondary attack rate of mpox among UK household contacts and determine factors associated with transmission to inform public health management of contacts, during the global outbreak in 2022. Information was collected via NHS and public health services and included age, gender, place of residence, setting, and type of contact. Aggregate information was summarized for the UK. Record level data was combined for England, Wales and Northern Ireland, and multivariable logistic regression was used to determine factors associated with transmission. The secondary attack rate among UK household mpox contacts was 4% (60/1 526). Sexual contact with the index case was associated with a 11-fold increase in adjusted odds of becoming a case in England, Wales, and Northern Ireland (95% CI 5.5-22, p < 0.001). Household contacts outside of London had increased odds compared to London residents (adjusted OR 2.9, 95%CI 1.6-5.4, p < 0.001), while female contacts had reduced odds of becoming a case (aOR: 0.41, 95% CI: 0.15-0.95). We found a low overall secondary attack rate among household mpox contacts with strong evidence of increased transmission risk associated with sexual contact. This evidence will inform the risk assessment of contacts and support prioritization of those with close intimate contact for follow up.

A prospective randomised controlled trial investigating household SARS-CoV-2 transmission in a densely populated community in Cape Town, South Africa - the transmission of COVID-19 in crowded environments (TRACE) study

BACKGROUND

South Africa's first SARS-CoV-2 case was identified 5th March 2020 and national lockdown followed March 26th. Households are an important location for secondary SARS-CoV-2 infection. Physical distancing and sanitation - infection mitigation recommended by the World Health Organization (WHO) at the time - are difficult to implement in limited-resource settings because of overcrowded living conditions.

METHODS

This study (ClinicalTrials.gov NCT05119348) was conducted from August 2020 to September 2021 in two densely populated, low socioeconomic Cape Town community sub-districts. New COVID-19 index cases (ICs) identified at public clinics were randomised to an infection mitigation intervention (STOPCOV) delivered by lay community health workers (CHWs) or standard of care group. STOPCOV mitigation measures included one initial household assessment conducted by a CHW in which face masks, sanitiser, bleach and written information on managing and preventing spread were provided. This was followed by regular telephonic follow-up from CHWs. SARS-CoV-2 PCR and IgM/IgG serology was performed at baseline, weeks 1, 2, 3 and 4 of follow-up.

RESULTS

The study randomised 81 ICs with 245 HHCs. At baseline, no HHCs in the control and 7 (5%) in the intervention group had prevalent SARS-CoV-2. The secondary infection rate (SIR) based on SARS-CoV-2 PCR testing was 1.9% (n = 2) in control and 2.9% (n = 4) in intervention HHCs (p = 0.598). At baseline, SARS-CoV-2 antibodies were present in 15% (16/108) of control and 38% (52/137) of intervention participants. At study end incidence was 8.3% (9/108) and 8.03% (11/137) in the intervention and control groups respectively. Antibodies were present in 23% (25/108) of control HHCs over the course of the study vs. 46% (63/137) in the intervention arm. CHWs made twelve clinic and 47 food parcel referrals for individuals in intervention households in need.

DISCUSSION

Participants had significant exposure to SARS-CoV-2 infections prior to the study. In this setting, household transmission mitigation was ineffective. However, CHWs may have facilitated other important healthcare and social referrals.

Identifying the interplay between protective measures and settings on the SARS-CoV-2 transmission using a Bayesian network

Contact tracing played a crucial role in minimizing the onward dissemination of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) in the recent pandemic. Previous studies had also shown the effectiveness of preventive measures such as mask-wearing, physical distancing, and exposure duration in reducing SARS-CoV-2 transmission. However, there is still a lack of understanding regarding the impact of various exposure settings on the spread of SARS-CoV-2 within the community, as well as the most effective preventive measures, considering the preventive measures adherence in different daily scenarios. We aimed to evaluate the effect of individual protective measures and exposure settings on the community transmission of SARS-CoV-2. Additionally, we aimed to investigate the interaction between different exposure settings and preventive measures in relation to such SARS-CoV-2 transmission. Routine SARS-CoV-2 contact tracing information was supplemented with additional data on individual measures and exposure settings collected from index patients and their close contacts. We used a case-control study design, where close contacts with a positive test for SARS-CoV-2 were classified as cases, and those with negative results classified as controls. We used the data collected from the case-control study to construct a Bayesian network (BN). BNs enable predictions for new scenarios when hypothetical information is introduced, making them particularly valuable in epidemiological studies. Our results showed that ventilation and time of exposure were the main factors for SARS-CoV-2 transmission. In long time exposure, ventilation was the most effective factor in reducing SARS-CoV-2, while masks and physical distance had on the other hand a minimal effect in this ventilation spaces. However, face masks and physical distance did reduce the risk in enclosed and unventilated spaces. Distance did not reduce the risk of infection when close contacts wore a mask. Home exposure presented a higher risk of SARS-CoV-2 transmission, and any preventive measures posed a similar risk across all exposure settings analyzed. Bayesian network analysis can assist decision-makers in refining public health campaigns, prioritizing resources for individuals at higher risk, and offering personalized guidance on specific protective measures tailored to different settings or environments.

Are we heroes or couriers? A phenomenological study on reappropriation of professional subjectivity and agency among health professionals during COVID-19 contact tracing in Türkiye

During the COVID-19 pandemic, Türkiye implemented a distinctive contact tracing approach involving in-person home visits by medical professionals to individuals who tested positive for the virus. This study examines the experiences of health professionals involved in contact tracing, exploring how they reappropriated their professional subjectivity and agency during their deployment in this role. It is an interpretive phenomenological qualitative study. We conducted 21 semi-structured in-depth interviews, subsequently carried out two separate focus group interviews with an additional 31 participants from various districts in Istanbul. Participants were selected from different medical professions (i.e. doctors, nurses, midwives), career stages, gender and age groups, and hierarchical levels (i.e. officers and directors). Data analysis was conducted collaboratively by the research team from sociology and public health disciplines. Our main finding is that for the majority of health professionals, contact tracing was a novel experience with challenges and ambivalances. Yet, regardless of their perceptions (positive, negative, or mixed), the experience promoted a reaffirmation of professional identity and reappropriation of professional subjectivity and agency, which discloses that professional subjectivity is not firm but dynamic, carrying stability as well as flexibility and adjustment. Four main themes are identified in their reappropriation of professional subjectivity and agency: uncovering professional fulfillment, feeling restrained in professional dissatisfaction, assessing the job, and engaging in professional and bureaucratic negotiations.The profound exploration into the dynamics of contact tracing amidst the pandemic illuminates a multidimensional narrative that transcends the conventional discourse on physical and psychological stress experienced by medical professionals. Contact tracing experience had a transformative impact on meaning and purpose of professional identity. Our findings highlight a need for a balanced approach between centralized decision-making, mobilization of professionals, quantitative evaluation, and professional autonomy and discretion, qualitative assessments, and meaningful engagement.

COVID-19 contact tracing and quarantine policies in the Indo-Pacific Region: A mixed-methods study of experiences of public health professionals

Contact tracing and quarantine are valuable public health tools to prevent the transmission of SARS-CoV-2 and control the epidemic. Many low-and middle-income countries (LMICs) adopted global contact tracing and quarantine guidelines but were unable to contextualise the guidance into policies and practices that were relevant to their setting. Therefore, we examine contact tracing policies and practices in the Indo-Pacific region and the need to design context-specific policies. We conducted a mixed-methods study, including a cross-sectional online survey followed by key-informant interviews (KIIs). Using convenience snowball sampling, we invited public health professionals primarily involved in COVID-19 pandemic response from the Indo-Pacific region. We undertook descriptive analyses using counts and percentages for survey data and framework analysis for qualitative data. Seventy-seven public health professionals participated in the survey, of whom ten also participated in the KIIs. The study identified significant gaps between policies and the local contexts. Factors that broaden the gaps were limited knowledge of the changing dynamics of COVID-19 transmission, poor leadership, and coordination, little or no formal training on contact tracing, poor understanding of the guideline recommendations, limited resources, community resistance and mistrust, social stigmatisation and fear of being ostracised, and discrimination. This study revealed substantial disparities between policies and local contexts, significantly influencing policy implementation at national, provincial, and district levels across the studied countries. To bridge these gaps, we advocate for national contact tracing and quarantine guidelines explicitly addressing the quarantine needs of specific demographics, including children, pregnant women, prisoners, and individuals affected by social exclusion issues. Furthermore, we propose strengthening contact tracing training programs, urging revised guidelines to account for social, cultural, and infrastructural nuances influencing contact tracing and quarantine implementation. We also recommend engaging local NGOs, faith-based organisations, and local administrations to reinforce community connections and strengthen contact tracing.

Looking under the lamp-post: quantifying the performance of contact tracing in the United States during the SARS-CoV-2 pandemic

Contact tracing forms a crucial part of the public-health toolbox in mitigating and understanding emergent pathogens and nascent disease outbreaks. Contact tracing in the United States was conducted during the pre-Omicron phase of the ongoing COVID-19 pandemic. This tracing relied on voluntary reporting and responses, often using rapid antigen tests due to lack of accessibility to PCR tests. These limitations, combined with SARS-CoV-2's propensity for asymptomatic transmission, raise the question "how reliable was contact tracing for COVID-19 in the United States"? We answered this question using a Markov model to examine the efficiency with which transmission could be detected based on the design and response rates of contact tracing studies in the United States. Our results suggest that contact tracing protocols in the U.S. are unlikely to have identified more than 1.65% (95% uncertainty interval: 1.62-1.68%) of transmission events with PCR testing and 1.00% (95% uncertainty interval 0.98-1.02%) with rapid antigen testing. When considering a more robust contact tracing scenario, based on compliance rates in East Asia with PCR testing, this increases to 62.7% (95% uncertainty interval: 62.6-62.8%). We did not assume presence of asymptomatic transmission or superspreading, making our estimates upper bounds on the actual percentages traced. These findings highlight the limitations in interpretability for studies of SARS-CoV-2 disease spread based on U.S. contact tracing and underscore the vulnerability of the population to future disease outbreaks, for SARS-CoV-2 and other pathogens.

Personal protective measures and settings on the risk of SARS-COV-2 community transmission: a case-control study

Background

During the SARS-CoV-2 pandemic, nurses of primary health care has been an important role in Spain. Even so, the data obtained in the tracing have been scarcely used to investigate the possible mechanisms of transmission. Few studies focused on community transmission, evaluating the effectiveness of individual protective measures and exposure environment. The main aim of the study was to evaluate the association between individual protective measures and SARS-CoV-2 transmission in the community and to compare secondary attack rates in different exposure settings.

Methods

A case-control study from contact tracing of SARS-CoV-2 index patients. COVID-19 contact tracing was led by nurses at the COVID-19 Coordinating Centre in Majorca (Spain). During the systematic tracing, additional information for this study was collected from the index patient (social-demographic variables, symptoms, the number of close contacts). And also, the following variables from their close contacts: contact place, ventilation characteristics mask-wearing, type of mask, duration of contact, shortest distance, case-contact relationship, household members, and handwashing, the test result for SARS-CoV-2 diagnostic. Close contacts with a positive test for SARS-CoV-2 were classified as "cases" and those negative as "controls."

Results

A total of 1,778 close contacts from 463 index patients were identified. No significant differences were observed between the sexes but between age groups. Overall Secondary Attack Rate (SAR) was 24.0% (95% CI: 22.0-26.0%), 36.9% (95% CI: 33.2-40.6%) in closed spaces without ventilation and 50.7% (95% CI: 45.6-55.8%) in exposure time > 24 h. A total of 49.2% of infections occurred among household members. Multivariate logistic regression analysis showed that open-air setting (OR 0.43, 95% CI: 0.27-0.71), exposure for less than 1 h (OR 0.19, 95% CI: 0.11-0.32), and wearing a mask (OR 0.49, 95% CI: 0.28-0.85) had a protective effect transmission of SARS-CoV-2 in the community.

Conclusion

Ventilation of the space, mask-wearing and shorter exposure time were associated with a lower risk of transmission in the community. The data obtained allowed an assessment of community transmission mechanisms and could have helped to improve and streamline tracing by identifying close contacts at higher risk.

Evaluation of mpox contact tracing activities and data collection in EU/EEA countries during the 2022 multicountry outbreak in nonendemic countries

To control human-to-human mpox transmission during the 2022 outbreak, European Union (EU)/European Economic Area (EEA) countries conducted case investigation and contact tracing (CT). We aimed to provide an overview of CT activities, describe CT data collection practices, and identify related facilitators, barriers, and potential opportunities for improvement. Between April 03, 2023 and May 12, 2023, a survey was distributed to CT stakeholders in 30 EU/EEA countries, asking about mpox CT activities and data collection and requesting to rank enablers, barriers, and improvements for CT on a five-point Likert scale. The 139 respondents from 27 countries indicated having performed case investigations (96%, n = 133), backward CT (88%, n = 122), forward CT (87%, n = 121), and follow-up on contacts' outcomes (77%, n = 107). Sixty percent (n = 80/134) used standardized data collection forms and 73% (n = 91/124) used databases. The highest-rated enablers were clear guidelines (mean = 3.9), quick access to laboratory results (3.6), and sufficient expertise (3.6). Highly rated barriers were inability to contact contacts (3.0) or cases (2.5) and lack of staff (2.4). The most needed improvements were availability of staff (3.5), expertise on affected populations (3.4) and data reporting tools and systems (3.3). To improve CT of mpox and diseases with similar transmission patterns, EU/EEA countries should increase workforce capacity in public and sexual health, offer training on CT operations and communication with affected communities, and use common CT data collection tools and systems.

Evaluating the Added Value of Digital Contact Tracing Support Tools for Citizens: Framework Development

BACKGROUND

The COVID-19 pandemic revealed that with high infection rates, health services conducting contact tracing (CT) could become overburdened, leading to limited or incomplete CT. Digital CT support (DCTS) tools are designed to mimic traditional CT, by transferring a part of or all the tasks of CT into the hands of citizens. Besides saving time for health services, these tools may help to increase the number of contacts retrieved during the contact identification process, quantity and quality of contact details, and speed of the contact notification process. The added value of DCTS tools for CT is currently unknown.

OBJECTIVE

To help determine whether DCTS tools could improve the effectiveness of CT, this study aims to develop a framework for the comprehensive assessment of these tools.

METHODS

A framework containing evaluation topics, research questions, accompanying study designs, and methods was developed based on consultations with CT experts from municipal public health services and national public health authorities, complemented with scientific literature.

RESULTS

These efforts resulted in a framework aiming to assist with the assessment of the following aspects of CT: speed; comprehensiveness; effectiveness with regard to contact notification; positive case detection; potential workload reduction of public health professionals; demographics related to adoption and reach; and user experiences of public health professionals, index cases, and contacts.

CONCLUSIONS

This framework provides guidance for researchers and policy makers in designing their own evaluation studies, the findings of which can help determine how and the extent to which DCTS tools should be implemented as a CT strategy for future infectious disease outbreaks.

Mpox knowledge, behaviours and barriers to public health measures among gay, bisexual and other men who have sex with men in the UK: a qualitative study to inform public health guidance and messaging

BACKGROUND

The 2022-23 mpox epidemic is the first-time sustained community transmission had been reported in countries without epidemiological links to endemic areas. During that period, the outbreak almost exclusively affected sexual networks of gay, bisexual, or other men who have sex with men (GBMSM) and people living with HIV. In efforts to control transmission, multiple public health measures were implemented, including vaccination, contact tracing and isolation. This study examines knowledge, attitudes, and perceptions of mpox among a sample of GBMSM during the 2022-23 outbreak in the UK, including facilitators for and barriers to the uptake of public health measures.

METHODS

Interviews were conducted with 44 GBMSM between May and December 2022. Data were analysed using reflexive thematic analysis. Positive and negative comments pertaining to public health measures were collated in a modified version of a 'table of changes' to inform optimisations to public health messages and guidance.

RESULTS

Most interviewees were well informed about mpox transmission mechanisms and were either willing to or currently adhering to public health measures, despite low perceptions of mpox severity. Measures that aligned with existing sexual health practices and norms were considered most acceptable. Connections to GBMSM networks and social media channels were found to increase exposure to sexual health information and norms influencing protective behaviours. Those excluded or marginalized from these networks found some measures challenging to perform or adhere to. Although social media was a key mode of information sharing, there were preferences for timely information from official sources to dispel exaggerated or misleading information.

CONCLUSIONS

There are differential needs, preferences, and experiences of GBMSM that limit the acceptability of some mitigation and prevention measures. Future public health interventions and campaigns should be co-designed in consultation with key groups and communities to ensure greater acceptability and credibility in different contexts and communities.

'We are not here to enforce; we are here for the people' Factors influencing performance of contact tracing during the COVID-19 pandemic: A qualitative study

Background

Provider-initiated contact tracing (CT) is an important measure to slow down the spread of infectious diseases such as COVID-19. However, carrying out effective CT depends on the collaboration between the patient and the contact tracer. To improve CT, it is important to understand which factors influence contact tracers in being able to carry out CT during large pandemics.

Methods

We performed individual semi-structured interviews with nine contact tracers working for the COVID-19 unit of the Public Health Service (PHS) Rotterdam-Rijnmond, the Netherlands, to explore their experiences with carrying out CT. Data were collected between July 2020 and December 2020. The interview protocol was structured based on the CT tasks and guided by the literature and the framework explaining adherence to clinical practice guidelines.

Results

In general, CT seemed to be carried out satisfactorily. Individual factors (interviewing techniques and skills, attitude towards the patient and attitude towards CT), factors related to the patient (cooperativeness and engagement, emotions, language and culture and (mis)information), guideline-related factors (characteristics) and factors related to the organisation (interactions with colleagues, support from management, workload and training) were found to influence the carrying out of CT.

Conclusion

To be well prepared for future pandemics, it is important to explore strategies that can be effective to support the contact tracer in performing CT, support patients in feeling comfortable to be engaged and ways to reach more consistency in policies and protocols.

Isolation and Quarantine for Coronavirus Disease 2019 in the United States, 2020-2022

BACKGROUND

Public health programs varied in ability to reach people with coronavirus disease 2019 (COVID-19) and their contacts to encourage separation from others. For both adult case patients with COVID-19 and their contacts, we estimated the impact of contact tracing activities on separation behaviors from January 2020 until March 2022.

METHODS

We used a probability-based panel survey of a nationally representative sample to gather data for estimates and comparisons.

RESULTS

An estimated 64 255 351 adults reported a positive severe acute respiratory syndrome coronavirus 2 test result; 79.6% isolated for ≥5 days, 60.2% isolated for ≥10 days, and 79.2% self-notified contacts. A total of, 24 057 139 (37.7%) completed a case investigation, and 46.2% of them reported contacts to health officials. More adults who completed a case investigation isolated than those who did not complete a case investigation (≥5 days, 82.6% vs 78.2%, respectively; ≥10 days, 69.8% vs 54.8%; both P < .05). A total of 84 946 636 adults were contacts of a COVID-19 case patient. Of these, 73.1% learned of their exposure directly from a case patient; 49.4% quarantined for ≥5 days, 18.7% quarantined for ≥14 days, and 13.5% completed a contact tracing call. More quarantined among those who completed a contact tracing call than among those who did not complete a tracing call (≥5 days, 61.2% vs 48.5%, respectively; ≥14 days, 25.2% vs 18.0%; both P < .05).

CONCLUSIONS

Engagement in contact tracing was positively correlated with isolation and quarantine. However, most adults with COVID-19 isolated and self-notified contacts regardless of whether the public health workforce was able to reach them. Identifying and reaching contacts was challenging and limited the ability to promote quarantining, and testing.

Rapid and sustained contact tracing training for COVID-19 in San Francisco: a training model for developing an emergency public health workforce

The City and County of San Francisco was the first municipality in the United States to institute a COVID-19 contact tracing program. The San Francisco Department of Public Health (SFDPH) and the University of California, San Francisco (UCSF) created an outcome-based fully remote contact tracing curriculum using participatory learning methods to train non-public health emergency workers as contact tracers. Between April and December 2020, we trained over 300 individuals in contact tracing skills and procedures over three training phases. Using iterative curriculum design and Kirkpatrick's evaluation methodology, we aimed to ensure high quality and successful person-centered contact tracing. The resulting curriculum consisted of 24 learning outcomes taught with six participatory skills development activities, asynchronous materials, and one-on-one contact tracer support. We collected more than 700 responses from trainees using various evaluation tools across the training phases, and contact tracers interviewed more than 24,000 contacts after training in our program. Our evaluations showed that knowledge and skills improved for most trainees and demonstrated the utility of the training program in preparing trainees to perform person-centered contact tracing in San Francisco. Local health jurisdictions and state health agencies can use this model of curriculum development and evaluation to rapidly train a non-public health workforce to respond to future public health emergencies.

Looking under the lamp-post: quantifying the performance of contact tracing in the United States during the SARS-CoV-2 pandemic

Contact tracing forms a crucial part of the public-health toolbox in mitigating and understanding emergent pathogens and nascent disease outbreaks. Contact tracing in the United States was conducted during the pre-Omicron phase of the ongoing COVID-19 pandemic. This tracing relied on voluntary reporting and responses, often using rapid antigen tests (with a high false negative rate) due to lack of accessibility to PCR tests. These limitations, combined with SARS-CoV-2's propensity for asymptomatic transmission, raise the question "how reliable was contact tracing for COVID-19 in the United States"? We answered this question using a Markov model to examine the efficiency with which transmission could be detected based on the design and response rates of contact tracing studies in the United States. Our results suggest that contact tracing protocols in the U.S. are unlikely to have identified more than 1.65% (95% uncertainty interval: 1.62%-1.68%) of transmission events with PCR testing and 0.88% (95% uncertainty interval 0.86%-0.89%) with rapid antigen testing. When considering an optimal scenario, based on compliance rates in East Asia with PCR testing, this increases to 62.7% (95% uncertainty interval: 62.6%-62.8%). These findings highlight the limitations in interpretability for studies of SARS-CoV-2 disease spread based on U.S. contact tracing and underscore the vulnerability of the population to future disease outbreaks, for SARS-CoV-2 and other pathogens.

Traversing missing links in the spread of HIV

Combining clinical and genetic data can improve the effectiveness of virus tracking with the aim of reducing the number of HIV cases by 2030.