Salmonellosis in Australia in 2020: possible impacts of COVID-19 related public health measures.

BACKGROUND: More than seventy per cent of salmonellosis in Australia is thought to be due to contaminated food. Rates of salmonellosis vary across the Australian states and territories, with the highest rates in the Northern Territory. In 2020, to control coronavirus disease 2019 (COVID-19), Australia implemented public health measures including border closures, physical distancing and hygiene advice. This study analyses salmonellosis notification rates in 2020 and considers possible impacts of COVID-19 measures. METHODS: Monthly and annual salmonellosis notifications per 100,000 population, for each of Australia's eight states and territories for the years 2015 to 2020, were extracted from Australia's publicly accessible National Notifiable Diseases Surveillance System. For each jurisdiction, the salmonellosis rate each month in 2020 was compared with the previous 5-year median rate for that calendar month. The possible impacts of COVID-19 public health measures on salmonellosis notifications in the respective states and territories were examined. RESULTS: The annual Australian salmonellosis notification rate was 27% lower in 2020 than the previous 5-year median. The reduction in salmonellosis rate varied throughout Australia. States and territories with more stringent, more frequent or longer COVID-19 public health measures had generally greater salmonellosis rate reductions. However, Tasmania had a 50% deeper reduction in salmonellosis rate than did the Northern Territory, despite similar restriction levels. CONCLUSIONS: Salmonellosis notifications decreased in Australia during the global COVID-19 pandemic. The reduction in notifications corresponded with the implementation of public health measures. Persistence of high rates in the Northern Territory could indicate the overarching importance of demographic and environmental factors.

COVID-19 outbreaks among crew on commercial ships at the Port of Rotterdam, the Netherlands, 2020 to 2021.

BackgroundDuring the COVID-19 pandemic, international shipping activity was disrupted as movement of people and goods was restricted. The Port of Rotterdam, the largest port in Europe, remained operational throughout.AimWe describe the burden of COVID-19 among crew on sea-going vessels at the port and recommend improvements in future infectious disease event notification and response at commercial ports.MethodsSuspected COVID-19 cases on sea-going vessels were notified to port authorities and public health (PH) authorities pre-arrival via the Maritime Declaration of Health. We linked data from port and PH information systems between 1 January 2020 and 31 July 2021, derived a notification rate (NR) of COVID-19 events per arrival, and an attack rate (AR) per vessel (confirmed cases). We compared AR by vessel type (workship/tanker/cargo/passenger), during wildtype-, alpha- and delta-dominant calendar periods.ResultsEighty-four COVID-19 events were notified on ships, involving 622 cases. The NR among 45,030 new arrivals was 173 per 100,000 impacting 1% of vessels. Events per week peaked in April 2021 and again in July 2021, when the AR was also highest. Half of all cases were notified on workships, events occurring earlier and more frequently than on other vessels.ConclusionNotification of COVID-19 events on ships occurred infrequently, although case under-ascertainment was likely. Pre-agreed protocols for data-sharing between stakeholders locally and across Europe would facilitate more efficient pandemic response. Public health access to specimens for sequencing and environmental sampling would give greater insight into viral spread on ships.

Early evidence of effectiveness of digital contact tracing for SARS-CoV-2 in Switzerland.

In the wake of the pandemic of coronavirus disease 2019 (COVID-19), contact tracing has become a key element of strategies to control the spread of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Given the rapid and intense spread of SARS-CoV-2, digital contact tracing has emerged as a potential complementary tool to support containment and mitigation efforts. Early modelling studies highlighted the potential of digital contact tracing to break transmission chains, and Google and Apple subsequently developed the Exposure Notification (EN) framework, making it available to the vast majority of smartphones. A growing number of governments have launched or announced EN-based contact tracing apps, but their effectiveness remains unknown. Here, we report early findings of the digital contact tracing app deployment in Switzerland. We demonstrate proof-of-principle that digital contact tracing reaches exposed contacts, who then test positive for SARS-CoV-2. This indicates that digital contact tracing is an effective complementary tool for controlling the spread of SARS-CoV-2. Continued technical improvement and international compatibility can further increase the efficacy, particularly also across country borders.

Impact of COVID-19 on foodborne illness in Africa - A perspective piece.

Food safety investments in Africa, through international donors or national programs, were primarily focused on the formal market sector. However, increasing consumer food safety concerns about foods sold in the growing informal food markets, the rising foodborne disease burden in Africa, and the emergence of COVID-19 have all made food safety a major concern and ultimately brought it to an inflection point in Africa. In addition, Data on foodborne disease outbreaks revealed a scarcity of reported cases before and during the pandemic. The lack of information on foodborne disease reporting in Africa translates into one of the reasons why food safety in Africa is becoming a rising subject matter. This perspective discusses the situation of food safety in Africa before and after the COVID-19 pandemic. Finally, challenges confronting ongoing efforts to improve food safety in the post-COVID era in Africa are summarized and highlighted.

[The preparedness of the Italian obstetric surveillance system in the response to the emergency of the SARS-CoV-2 pandemic: methodological aspects of a population-based study]. / La preparedness dell'Italian obstetric surveillance system in occasione della pandemia da SARS-CoV-2: aspetti metodologici di uno studio di popolazione.

This paper aims to describe the Italian obstetric surveillance system (ItOSS) preparedness as an element for a timely response to the new Coronavirus pandemic. ItOSS is a surveillance network that has been collecting data on maternal mortality and conducting population studies on obstetric near misses since 2013. At the beginning of the pandemic, ItOSS launched a new population-based project to monitor SARS-CoV-2 infection during pregnancy and post-partum and promptly give back information useful to clinicians and decision-makers. All the regions and autonomous provinces, for a total of 289 birth units (PN), joined the study. Data relating to pregnant or post-partum women with a confirmed SARS-CoV-2 infection diagnosis addressing the maternities for outpatient visits or hospitalization were collected. The project methodology entails that each participating maternity reports the cases to ItOSS uploading data through an open-source platform. The on-line form includes sociodemographic and clinical data and maternal-neonatal outcomes. Biological samples to detect possible vertical transmission are also collected voluntarily. A total of 534 incident cases were reported from February 25th to July 10th 2020; 7 regions also collected biological samples for 227 cases; data collection is still ongoing.A preliminary analysis of the first 146 SARS-CoV-2 positive women who gave birth between February 25th to April 22nd shows an incidence rate of the infection equal to 2.1/1,000 in Italy and 6.9/1,000 in the Lombardy Region (Northern Italy). The brief time needed to setting up and operating the project, the national coverage, the adoption of shared tools for data collection, the quality and completeness of the information collected show how the availability of active networks like ItOSS represents a crucial element to hold a high level of preparedness in case of a health emergency.

Impact of COVID-19 pandemic on notifiable diseases in Northern Brazil / Impacto da COVID-19 em doenças de notificação compulsória no Norte do Brasil / Impacto de la COVID-19 en las enfermedades de notificación compulsoria del Norte de Brasil

Objetivo: Avaliar o impacto da pandemia COVID-19 em doenças de notificação compulsória no Norte do Brasil. Métodos: Estudo descritivo e retrospectivo realizado com dados das bases Sinan (Sistema de Informação de Agravos de Notificação) e SIH/SUS (Sistema de Informações Hospitalares do SUS) sobre meningite bacteriana e viral, dengue, febre hemorrágica da dengue, arboviroses, sífilis, tuberculose, hanseníase e hepatites virais. Utilizou-se estatística descritiva para avaliação da variação nos números absolutos das notificações e internações do período de 2015 a 2020 e suas variações médias. Resultados: As notificações e internações de meningite, arboviroses não-dengue, hanseníase, leptospirose e hepatites virais, em geral, demonstraram redução de 50 até 80% em relação a períodos anteriores. Houve variabilidade regional com dengue e febre hemorrágica da dengue, com aumentos e reduções independentes. As sífilis adquirida, gestacional e congênita demonstraram queda de até 60% nas notificações e nas internações, exceto sífilis congênita, que se manteve em estabilidade. As notificações e as internações de tuberculose se mantiveram estáveis em toda a região. Conclusão: Houve redução geral de mais da metade das notificações e das internações hospitalares, apresentando um impacto variável, dependendo do Estado e do processo de endemia de cada sub-região.

Objective: To assess the impact of the COVID-19 pandemic on notifiable diseases in Northern Brazil. Methods: A descriptive retrospective study was conducted using data from the Notifiable Disease Information System (Sistema de Informação de Agravos de Notificação ­ Sinan) and SUS Hospital Information System (Sistema de Informações Hospitalares do SUS ­ SIH/SUS) on bacterial and viral meningitis, dengue, dengue hemorrhagic fever, arboviruses, syphilis, tuberculosis, leprosy, and viral hepatitis. Descriptive statistics was used to assess the variation in absolute numbers of notifications and hospitalizations from 2015 to 2020 and their average variations. Results: Notifications and hospitalizations for meningitis, non-dengue arboviruses, leprosy, leptospirosis, and viral hepatitis exhibited a general decrease of 50 to 80% compared to previous years. There was regional variation in dengue and dengue hemorrhagic fever, with independent increases and decreases. Acquired, gestational and congenital syphilis presented a 60% decrease in notifications and hospitalizations, except for congenital syphilis, which remained stable. Tuberculosis notifications and hospitalizations remained stable in the entire region. Conclusion: There was an overall decrease of more than a half of notifications and hospitalizations, representing a variable impact depending on the state and the endemic process of each subregion.

Objetivo: Evaluar el impacto de la pandemia de la COVID-19 en las enfermedades de notificación compulsoria del Norte de Brasil. Métodos: Estudio descriptivo y retrospectivo realizado con datos de las bases SINAN (Sistema de Información de Agravios de Notificación) y SIH/SUS (Sistema de Informaciones Hospitalarias del SUS) sobre la meningitis bacteriana y viral, el dengue, la fiebre hemorrágica del dengue, las arbovirosis, la sífilis, la tuberculosis, la lepra y las hepatitis virales. Se utilizó de la estadística descriptiva para la evaluación de la variación de los números absolutos de las notificaciones y los ingresos del periodo entre 2015 y 2020 y sus variaciones medias. Resultados: Las notificaciones y los ingresos de meningitis, arbovirosis no-dengue,la lepra, la leptospirosis y las hepatitis virales, en general, han demostrado una disminución del 50 hasta el 80% respecto los periodos anteriores. Hubo variabilidad por región respecto el dengue y fiebre hemorrágica del dengue con subidas y bajadas independientes. Las sífilis adquirida, gestacional y congénita han demostrado caída hasta el 60% de las notificaciones e ingresos excepto la sífilis congénita que se mantuvo estable. Las notificaciones y los ingresos por tuberculosis se mantuvieron estables em toda la región. Conclusión: Hubo una disminución general de más de la mitad de las notificaciones y los ingresos hospitalarios, presentando un impacto variable, a depender del Estado y del proceso de endemia de cada sub-región.

[Impact of COVID-19 epidemic on syphilis case reporting in China].

Objective: To analyze the impact of COVID-19 epidemic on syphilis case reporting in China, and provide evidence to evaluate the epidemic situation of syphilis and strengthen the prevention and control of syphilis during COVID-19 epidemic. Methods: The data were collected from the National Notifiable Infectious Disease Reporting System of China Information System for Disease Control and Prevention, National STD Management Information System, and the "nCov2019" R package of github website. The changes of reported cases of syphilis before and during COVID-19 epidemic in China were analyzed. Joinpoint regression model was established by using the reported case number of syphilis from 2010 to 2018, the data in 2019 was used for validation, and the number of syphilis cases in 2020 and 2021 was predicted. The impact of COVID-19 epidemic on the number of syphilis cases was evaluated with calculating the percentage error (PE) between actual number and predicted number of syphilis cases reported.The correlation between reported cases of syphilis and COVID-19 was analyzed by Spearman's correlation analysis. The softwares of Joinpoint 4.9.1.0 and SPSS 18.0 were used for statistical analysis. Results: In 2020 and 2021, the reported cases of syphilis in China decreased significantly by 13.32% and 10.41%, respectively, compared with 2019 (before COVID-19 epidemic), and the reported cases of syphilis in 2021 increased by 3.36% compared with 2020. The reported cases of syphilis in 2020 and 2021 decreased by 17.95% and 20.41%, respectively, compared with predicted numbers. From January to March 2020, the reported monthly case number of syphilis was completely negatively correlated with the confirmed case number of COVID-19 (rs=-1.00, P<0.001). In the provinces with different scales of COVID-19 epidemic, there was also a negative correlation between the monthly reported case number of syphilis and confirmed case number of COVID-19 (all P<0.05). Conclusions: In China, the change of reported cases of syphilis was closely associated with COVID-19 epidemic in 2020 and 2021. Due to the influence of COVID-19 epidemic, the number of reported cases of syphilis decreased significantly, but it should not be thought that syphilis incidence will become a decline trend in the future. It is necessary to carefully and scientifically assess the changes in syphilis epidemic.

Estimated Cases Averted by COVID-19 Digital Exposure Notification, Pennsylvania, USA, November 8, 2020-January 2, 2021.

We combined field-based data with mathematical modeling to estimate the effectiveness of smartphone-enabled COVID-19 exposure notification in Pennsylvania, USA. We estimated that digital notifications potentially averted 7-69 cases/1,000 notifications during November 8, 2020-January 2, 2021. Greater use and increased compliance could increase the effectiveness of digital notifications.

An evaluation of the notifiable disease surveillance system in Chegutu District, Zimbabwe, 2020: a cross-sectional study.

Introduction: in 2018-2019 Chegutu District had one notification form Tally 1 (T1) that was completed instead of seven for detected notifiable diseases. Different figures of cholera were reported through weekly rapid disease notification system with 106 patients and Notifiable Diseases Surveillance System (NDSS) with 111 patients, causing data discrepancy. We evaluated the NDSS to determine reasons for underperformance and data discrepancy. Methods: we conducted descriptive cross-sectional study using updated centres for disease control and prevention guidelines for surveillance system evaluation. We recruited forty-six health workers. Interviewer-administered questionnaires and checklists were used to collect data on reasons for underperformance, reasons for data discrepancy, knowledge of NDSS, surveillance system attributes and usefulness. Epi InfoTM7 generated frequencies, proportions, and means. Likert scale was used to assess health worker knowledge. Results: of the forty-six health workers, 34 (78%) had fair knowledge of NDSS. The reason for system underperformance was lack of training in NDSS 42 (91%). Data discrepancy was attributed to typographical mistakes made during data entry on WhatsApp platform 32 (70%). Eighty per cent (37) were willing to complete T1 forms. Six participants who were timed took ten minutes to complete T1 forms. Among 17 health facilities, only three had fifteen T1 forms that were adequate to notify first five cases in an outbreak. Notifiable diseases surveillance system data was used for planning health education 28 (68%). Conclusion: the NDSS was unstable due to health workers' inadequate knowledge and unavailability of T1 forms. Notifiable diseases surveillance system was found to be simple, acceptable, and useful. We recommended NDSS training of health workers.

Defining Key Performance Indicators for the California COVID-19 Exposure Notification System (CA Notify).

OBJECTIVES: Toward common methods for system monitoring and evaluation, we proposed a key performance indicator framework and discussed lessons learned while implementing a statewide exposure notification (EN) system in California during the COVID-19 epidemic. MATERIALS AND METHODS: California deployed the Google Apple Exposure Notification framework, branded CA Notify, on December 10, 2020, to supplement traditional COVID-19 contact tracing programs. For system evaluation, we defined 6 key performance indicators: adoption, retention, sharing of unique codes, identification of potential contacts, behavior change, and impact. We aggregated and analyzed data from December 10, 2020, to July 1, 2021, in compliance with the CA Notify privacy policy. RESULTS: We estimated CA Notify adoption at nearly 11 million smartphone activations during the study period. Among 1 654 201 CA Notify users who received a positive test result for SARS-CoV-2, 446 634 (27%) shared their unique code, leading to ENs for other CA Notify users who were in close proximity to the SARS-CoV-2-positive individual. We identified at least 122 970 CA Notify users as contacts through this process. Contact identification occurred a median of 4 days after symptom onset or specimen collection date of the user who received a positive test result for SARS-CoV-2. PRACTICE IMPLICATIONS: Smartphone-based EN systems are promising new tools to supplement traditional contact tracing and public health interventions, particularly when efficient scaling is not feasible for other approaches. Methods to collect and interpret appropriate measures of system performance must be refined while maintaining trust and privacy.

Public Willingness to Engage With COVID-19 Contact Tracing, Quarantine, and Exposure Notification.

OBJECTIVES: We conducted a survey to understand how people's willingness to share information with contact tracers, quarantine after a COVID-19 exposure, or activate and use a smartphone exposure notification (EN) application (app) differed by the person or organization making the request or recommendation. METHODS: We analyzed data from a nationally representative survey with hypothetical scenarios asking participants (N = 2157) to engage in a public health action by health care providers, public health departments, employers, and others. We used Likert scales and ordered logistic regression to compare willingness to take action based on which person or organization made the request, and we summarized findings by race and ethnicity. RESULTS: The highest levels of willingness to engage in contact tracing (adjusted odds ratio [aOR] = 1.74; 95% CI, 1.55-1.96), quarantine (aOR = 1.91; 95% CI, 1.69-2.15), download/activate an EN app (aOR = 1.30; 95% CI, 1.16-1.46), and notify other EN users (aOR = 1.43; 95% CI, 1.27-1.60) were reported when the request came from the participant's personal health care provider rather than from federal public health authorities. When compared with non-Hispanic White participants, non-Hispanic Black participants reported significantly higher levels of willingness to engage in contact tracing (aOR = 1.32; 95% CI, 1.18-1.48), quarantine (aOR = 1.49; 95% CI, 1.37-1.63), download/activate an EN app (aOR = 2.19; 95% CI, 2.01-2.38), and notify other EN users (aOR = 1.63; 95% CI, 1.49-1.79). CONCLUSIONS: Partnering with individuals and organizations perceived as trustworthy may help influence people expressing a lower level of willingness to engage in each activity, while those expressing a higher level of willingness to engage in each activity may benefit from targeted communications.

Trading-off privacy and utility: the Washington State experience assessing the performance of a public health digital exposure notification system for coronavirus disease 2019.

OBJECTIVE: Digital exposure notifications (DEN) systems were an emergency response to the coronavirus disease 2019 (COVID-19) pandemic, harnessing smartphone-based technology to enhance conventional pandemic response strategies such as contact tracing. We identify and describe performance measurement constructs relevant to the implementation of DEN tools: (1) reach (number of users enrolled in the intervention); (2) engagement (utilization of the intervention); and (3) effectiveness in preventing transmissions of COVID-19 (impact of the intervention). We also describe WA State's experience utilizing these constructs to design data-driven evaluation approaches. METHODS: We conducted an environmental scan of DEN documentation and relevant publications. Participation in multidisciplinary collaborative environments facilitated shared learning. Compilation of available data sources and their relevance to implementation and operation workflows were synthesized to develop implementation evaluation constructs. RESULTS: We identified 8 useful performance indicators within reach, engagement, and effectiveness constructs. DISCUSSION: We use implementation science to frame the evaluation of DEN tools by linking the theoretical constructs with the metrics available in the underlying disparate, deidentified, and aggregate data infrastructure. Our challenges in developing meaningful metrics include limited data science competencies in public health, validation of analytic methodologies in the complex and evolving pandemic environment, and the lack of integration with the public health infrastructure. CONCLUSION: Continued collaboration and multidisciplinary consensus activities can improve the utility of DEN tools for future public health emergencies.

Evaluating COVID-19 Exposure Notification Effectiveness With SimAEN: A Simulation Tool Designed for Public Health Decision Making.

OBJECTIVES: Exposure notification (EN) supplements traditional contact tracing by using proximity sensors in smartphones to record close contact between persons. This ledger is used to alert persons of potential SARS-CoV-2 exposure, so they can quarantine until their infection status is determined. We describe a model that estimates the impact of EN implementation on reducing the spread of SARS-CoV-2 and on the workload of public health officials, in combination with other key public health interventions such as traditional contact tracing, face mask wearing, and testing. METHODS: We created an agent-based model, Simulated Automated Exposure Notification (SimAEN), to explore the effectiveness of EN to slow the spread of SARS-CoV-2. We varied selected simulation variables, such as population adoption of EN and EN detector sensitivity configurations, to illustrate the potential effects of EN. We executed 20 simulations with SimAEN for each scenario and derived results for each simulation. RESULTS: When more sensitive versus more specific EN configurations were compared, the effective reproductive number, RE, was minimally affected (a decrease <0.03). For scenarios with increasing levels of EN adoption, an increasing number of additional infected persons were identified through EN, and total infection counts in the simulated population decreased; RE values for this scenario decreased with increasing EN adoption (a decrease of 0.1 to 0.2 depending on the scenario). CONCLUSIONS: Estimates from SimAEN can help public health officials determine which levels of EN adoption in combination with other public health interventions can maximize prevention of COVID-19 while minimizing unnecessary quarantine in their jurisdiction.

Creutzfeldt-Jakob disease surveillance in Australia: update to 31 December 2021.

Nationwide surveillance of Creutzfeldt-Jakob disease (CJD) and other human prion diseases is performed by the Australian National Creutzfeldt-Jakob Disease Registry (ANCJDR). National surveillance encompasses the period since 1 January 1970, with prospective surveillance occurring from 1 October 1993. Over this prospective surveillance period, considerable developments have occurred in pre-mortem diagnostics; in the delineation of new disease subtypes; and in a heightened awareness of prion diseases in healthcare settings. Surveillance practices of the ANCJDR have evolved and adapted accordingly. This report summarises the activities of the ANCJDR during 2021. Since the ANCJDR began offering diagnostic cerebrospinal fluid (CSF) 14-3-3 protein testing in Australia in September 1997, the annual number of referrals has steadily increased. In 2021, a total of 548 domestic CSF specimens were referred for 14-3-3 protein testing; 73 persons with suspected human prion disease were formally added to the national register. As of 31 December 2021, just over half of the 73 suspect case notifications (37/73) remain classified as 'incomplete'; 17 cases were classified as 'definite' and 13 as 'probable' prion disease; six cases were excluded through either detailed clinical follow-up (two cases) or neuropathological examination (four cases). For 2021, sixty-four percent of all suspected human-prion-disease-related deaths in Australia underwent neuropathological examination. No cases of variant or iatrogenic CJD were identified. The SARS-CoV-2 pandemic did not affect prion disease surveillance outcomes in Australia.

Engagement in Protective Behaviors by Digital Exposure Notification Users During the COVID-19 Pandemic, Washington State, January-June 2021.

OBJECTIVES: Smartphone-based digital exposure notification (EN) tools were introduced during the COVID-19 pandemic to supplement strained case investigation and contact tracing efforts. We examined the influence of an EN tool implemented in Washington State, WA Notify, on user engagement in behaviors that protect against COVID-19 transmission. METHODS: From January 25 through June 30, 2021, we administered 2 surveys to WA Notify users who received notification of a possible COVID-19 exposure. The initial survey, sent when users received a notification, focused on intent to engage in protective behaviors. The follow-up survey captured data on self-reported actual engagement in protective behaviors and contact by a public health contact tracer. RESULTS: Of 1507 WA Notify users who completed the initial survey, 40.1% (n = 604) reported intending to seek COVID-19 testing and 67.1% (n = 1011) intended to watch for COVID-19 symptoms. Of 407 respondents to the follow-up survey, 57.5% (n = 234) reported getting tested and 84.3% (n = 343) reported watching for COVID-19 symptoms. Approximately 84% (n = 1266) of respondents to the initial survey received a notification from WA Notify before being reached by public health contact tracers; on follow-up, 42.5% (n = 173) of respondents reported never being contacted by public health. CONCLUSIONS: Our findings suggest that WA Notify users may initiate protective behaviors earlier than nonusers who will not know of an exposure until notified by public health or by a known contact. Digital EN tools may be a valuable addition to existing public health outbreak investigation and response activities.

Quantifying SARS-CoV-2 Infection Risk Within the Google/Apple Exposure Notification Framework to Inform Quarantine Recommendations.

Most early Bluetooth-based exposure notification apps use three binary classifications to recommend quarantine following SARS-CoV-2 exposure: a window of infectiousness in the transmitter, ≥15 minutes duration, and Bluetooth attenuation below a threshold. However, Bluetooth attenuation is not a reliable measure of distance, and infection risk is not a binary function of distance, nor duration, nor timing. We model uncertainty in the shape and orientation of an exhaled virus-containing plume and in inhalation parameters, and measure uncertainty in distance as a function of Bluetooth attenuation. We calculate expected dose by combining this with estimated infectiousness based on timing relative to symptom onset. We calibrate an exponential dose-response curve based on infection probabilities of household contacts. The probability of current or future infectiousness, conditioned on how long postexposure an exposed individual has been symptom-free, decreases during quarantine, with shape determined by incubation periods, proportion of asymptomatic cases, and asymptomatic shedding durations. It can be adjusted for negative test results using Bayes' theorem. We capture a 10-fold range of risk using six infectiousness values, 11-fold range using three Bluetooth attenuation bins, ∼sixfold range from exposure duration given the 30 minute duration cap imposed by the Google/Apple v1.1, and ∼11-fold between the beginning and end of 14 day quarantine. Public health authorities can either set a threshold on initial infection risk to determine 14-day quarantine onset, or on the conditional probability of current and future infectiousness conditions to determine both quarantine and duration.

Drivers of downloading and reasons for not downloading COVID-19 contact tracing and exposure notification apps: A national cross-sectional survey.

BACKGROUND: Bluetooth-enabled smartphone apps have been developed and implemented in different sites globally to help overcome capacity limitations of traditional interview-based COVID-19 contact tracing. Two apps are currently available in Canada: ABTraceTogether exclusively in Alberta and COVID Alert in nine other provinces and territories. This study aims to examine factors associated with downloading of these apps to inform targeted promotion and marketing to increase app uptake. METHODS: We performed a cross-sectional survey with adult participants (≥18 years old) from an online national panel. Participants were asked if they had downloaded an app and, if applicable, reasons for not downloading. Logistic regression was used to identify sociodemographic factors and trusted information sources associated with downloading and reasons for not downloading. RESULTS: Of the included 4,503 respondents (36% response rate), 1,394 (31%) had downloaded an app. Demographic and socioeconomic factors positively associated with app download were: 1) being female, 2) higher household income, 3) higher education level attained, and 4) more liberal political views. The odds of downloading an app were higher for participants who trusted health-related information sources, and lower for those who trusted internet searches, family and friend, or Facebook. The most cited reasons for not downloading were related to data security concerns and perceived lack of benefit from the apps. INTERPRETATION: These findings identify sociodemographic segments with the lowest app uptake, reasons for not downloading and trusted information sources to inform targeted promotion and marketing strategies to improve uptake of apps to facilitate contact tracing.