We describe projections for the burden of infections and deaths in King and Snohomish Counties through April 7, as projections further out are strongly sensitive to assumptions about the scale of the local outbreak and importation dynamics from other regions that are not yet known. For the projections, we considered four scenarios for the increasingly effective impact of social distancing on COVID-19 incidence: • A baseline scenario assuming no change since January 15. • Scenarios with 25, 50, and 75 percent reductions in the rate of transmission assumed to take place starting March 10. The scenarios describe the generalized impacts of social distancing policies but do not currently speak to specific policy recommendations on issues like school closures, event cancellation, and work policies. We estimate that in the baseline scenario, on average across multiple simulations, there will have been roughly 25,000 people infected by April 7. Assuming mortality statistics will be like those seen in China, we expect that roughly 80 deaths will have occurred by April 7 and that roughly 400 total deaths will have been destined but not yet occurred. Effective social distancing slows the growth rate of the epidemic, and very effective interventions may stop the continued exponential growth. The table below illustrates the reductions in infections and deaths we expect with social distancing interventions. Social distancing intervention Estimated infections Destined deaths Business as usual 25,000 400 25% reduction 9,700 160 50% reduction 4,800 100 75% reduction 1,700 30 We do not yet know which scenario best represents current conditions in King and Snohomish counties, but previous experience in the region with weather-related social distancing and in other countries suggests to us that current efforts will likely land between baseline and 25% reduction scenarios. While we are not yet confident in our ability to estimate when the volume of new infections will overwhelm the health system, we discuss the issue below and believe it will be a critically important issue to address in the weeks to come. Thus, we believe more comprehensive non-pharmaceutical intervention policies in the region as soon as possible will be necessary to slow the onslaught of the disease, and we hope these are accompanied by policies to mitigate the broader societal impacts on the healthcare workforce and vulnerable populations.
Introduction. While influenza and other respiratory pathogens cause significant morbidity and mortality, the community-based burden of these infections remains incompletely understood. The development of novel methods to detect respiratory infections is essential for mitigating epidemics and developing pandemic-preparedness infrastructure. Methods. From October 2019 to March 2020, we conducted a home-based cross-sectional study in the greater Seattle area, utilizing electronic consent and data collection instruments. Participants received nasal swab collection kits via rapid delivery within 24 hours of self-reporting respiratory symptoms. Samples were returned to the laboratory and were screened for 26 respiratory pathogens and a housekeeping gene. Participant data were recorded via online survey at the time of sample collection and one week later. Results. Of the 4,572 consented participants, 4,359 (95.3%) received a home swab kit, and 3,648 (83.7%) returned a nasal specimen for respiratory pathogen screening. The 3,638 testable samples had a mean RNase P CRT value of 19.0 (SD: 3.4) and 1,232 (33.9%) samples had positive results for one or more pathogens, including 645 (17.7%) influenza-positive specimens. Among the testable samples, the median time between shipment of the home swab kit and completion of laboratory testing was 8 days [IQR: 7.0-14.0]. A single adverse event occurred and did not cause long-term effects or require medical attention. Discussion. Home-based surveillance using online participant enrollment and specimen self-collection is a safe and feasible method for community-level monitoring of influenza and other respiratory pathogens, which can readily be adapted for use during pandemics.
Introduction.While seasonal influenza and other respiratory pathogens cause significant morbidity and mortality each year, the community-based burden of these infections remains incompletely understood. Understanding the prevalence, epidemiology, and transmission dynamics of respiratory pathogen infections among community-dwelling individuals is essential during pandemic and epidemic settings and for developing pandemic-preparedness infrastructure. Methods and Analysis.We present the protocol for a novel, city-wide home-based cross-sectional study in the Seattle Metropolitan area, utilizing rapid delivery systems for self-collection of a nasal swab and return to the laboratory for respiratory pathogen testing. All participation takes place electronically, including recruitment, consent, and data collection. Within 48 hours of participants self-reporting respiratory symptoms, a nasal swab kit is delivered to the household via a courier service. Demographic and illness characteristics are collected at the time of sample collection and recovery and behavioral information collected one week later. Specimens are tested in the laboratory for multiple respiratory pathogens, and results are available on a public website for participants.Ethics and Dissemination. The study was approved by the University of Washington Institutional Review Board (Protocol #00006181). Results will be disseminated through peer-reviewed publications, talks at conferences, and on the Study Website ( www.seattleflu.org ).All rights reserved. No reuse allowed without permission. author/funder, who has granted medRxiv a license to display the preprint in perpetuity. Article Summary:• The findings of this study will inform whether a home-based approach to city-wide respiratory surveillance is possible in epidemic settings • A key strength of this study is that it is conducted across diverse neighborhoods spanning a major metropolitan area • Clinical findings may not be generalizable, as they are reliant on self-report (vaccination status, symptoms, healthcare utilization, etc.) All rights reserved. No reuse allowed without permission.author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
IntroductionWhile influenza and other respiratory pathogens cause significant morbidity and mortality, the community-based burden of these infections remains incompletely understood. The development of novel methods to detect respiratory infections is essential for mitigating epidemics and developing pandemic-preparedness infrastructure.MethodsFrom October 2019 to March 2020, we conducted a home-based cross-sectional study in the greater Seattle area, utilizing electronic consent and data collection instruments. Participants received nasal swab collection kits via rapid delivery within 24 hours of self-reporting respiratory symptoms. Samples were returned to the laboratory and were screened for 26 respiratory pathogens and a human marker. Participant data were recorded via online survey at the time of sample collection and one week later.ResultsOf the 4,572 consented participants, 4,359 (95.3%) received a home swab kit, and 3,648 (83.7%) returned a nasal specimen for respiratory pathogen screening. The 3,638 testable samples had a mean RNase P CRT value of 19.0 (SD: 3.4) and 1,232 (33.9%) samples had positive results for one or more pathogens, including 645 (17.7%) influenza-positive specimens. Among the testable samples, the median time between shipment of the home swab kit and completion of laboratory testing was 8 days [IQR: 7.0-14.0].DiscussionHome-based surveillance using online participant enrollment and specimen self-collection is a feasible method for community-level monitoring of influenza and other respiratory pathogens, which can readily be adapted for use during pandemics.
Background Rapid diagnostic tests (RDTs) for influenza used by individuals at home could potentially expand access to testing and reduce the impact of influenza on health systems. Improving access to testing could lead to earlier diagnosis following symptom onset, allowing more rapid interventions for those who test positive, including behavioral changes to minimize spread. However, the accuracy of RDTs for influenza has not been determined in self-testing populations. Objective This study aims to assess the accuracy of an influenza RDT conducted at home by lay users with acute respiratory illness compared with that of a self-collected sample by the same individual mailed to a laboratory for reference testing. Methods We conducted a comparative accuracy study of an at-home influenza RDT (Ellume) in a convenience sample of individuals experiencing acute respiratory illness symptoms. Participants were enrolled in February and March 2020 from the Greater Seattle region in Washington, United States. Participants were mailed the influenza RDT and reference sample collection materials, which they completed and returned for quantitative reverse-transcription polymerase chain reaction influenza testing in a central laboratory. We explored the impact of age, influenza type, duration, and severity of symptoms on RDT accuracy and on cycle threshold for influenza virus and ribonuclease P, a marker of human DNA. Results A total of 605 participants completed all study steps and were included in our analysis, of whom 87 (14.4%) tested positive for influenza by quantitative reverse-transcription polymerase chain reaction (70/87, 80% for influenza A and 17/87, 20% for influenza B). The overall sensitivity and specificity of the RDT compared with the reference test were 61% (95% CI 50%-71%) and 95% (95% CI 93%-97%), respectively. Among individuals with symptom onset ≤72 hours, sensitivity was 63% (95% CI 48%-76%) and specificity was 94% (95% CI 91%-97%), whereas, for those with duration >72 hours, sensitivity and specificity were 58% (95% CI 41%-74%) and 96% (95% CI 93%-98%), respectively. Viral load on reference swabs was negatively correlated with symptom onset, and quantities of the endogenous marker gene ribonuclease P did not differ among reference standard positive and negative groups, age groups, or influenza subtypes. The RDT did not have higher sensitivity or specificity among those who reported more severe illnesses. Conclusions The sensitivity and specificity of the self-test were comparable with those of influenza RDTs used in clinical settings. False-negative self-test results were more common when the test was used after 72 hours of symptom onset but were not related to inadequate swab collection or severity of illness. Therefore, the deployment of home tests may provide a valuable tool to support the management of influenza and other respiratory infections.
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