Sars-CoV-2 PCR persistence and review of population swabbing in QLD's first wave

Kylie Alcorn, Paulina Stehlik, Andre Wattiaux, Sanmarie Schlebusch, Anna Jones, David A Henry

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Introduction: A cornerstone of the public health response to Sars-CoV-2 has been isolation of positive patients. Initially, criteria for release from isolation required two negative swabs in addition to symptom criteria; however, this phased out by June 4 as viral RNA can persist as ‘viral litter’ with little implication on infectivity.¹,² The large collection of repeat tests prior to June 4 enabled a review of local demographic characteristics for swabbed individuals and duration of RNA persistence. Methods: We conducted an exploratory analysis of Queensland's (QLD) pathology SARS-CoV-2 reverse transcriptase polymerase chain reaction (RT-PCR) test results. Kaplan Meier analysis was used to estimate time to viral clearance and Cox regression to explore effects of age and sex. Results: We analysed 97 476 individuals’ results between January 19 and June 4 2020. Median age was 41y (range <1-105y), 57.2% (95% CI 57.2, 57.2) were female, and 958 individuals (0.98%; 95% CI 0.92,1.05) tested positive for SARS-CoV-2. Positivity rates were lower in regional areas than cities, in females (OR 0.80, 95% CI 0.70, 0.91), and in those aged 16y and below (p<0.01, test for trend).Of the 958 positive individuals, 243 had two or more (max 17) additional tests, and 92% (95% CI 88.1, 95.2) remained positive after 10 days (max 76 days) after the initial result. Median time to apparent viral clearance was longer in those 65y and over compared to those under 65y (29 v 43 days, HR 1.85; 95% CI 1.17, 2.90), and was unaffected by sex (HR 0.93; 95% CI 0.66, 1.30).Conclusion: Detectable RNA can persist for long periods of time, particularly in the elderly. REF:1. Wolfel R, et al. Virological assessment of hospitalized patients with COVID-2019. Nature. 2020;581(7809):465-9.2. Why some Covid-19 patients might have tested positive twice. Quartz April 16 2020.
Original languageEnglish
Number of pages1
Publication statusPublished - Dec 2020
EventAustralasian COVID19 Virtual Conference: Preventing, detective, controlling and managing COVID19 - reflections on 2020 and future challenges - Online
Duration: 8 Dec 202010 Dec 2020
Conference number: Special Edition


ConferenceAustralasian COVID19 Virtual Conference
OtherThe Special Edition - Australasian COVID-19 Virtual Conference will be held from Tuesday 8 to Thursday 10 December 2020 and is convened by the Communicable Diseases Network Australia, the Public Health Laboratory Network, the Australasian Society for Infectious Diseases and the Public Health Association of Australia.

While COVID-19 unfolds as the biggest health crisis in a century, it is vital to take time out to review and share the experiences and lessons learned to date. We also aim to bring together the experts to think through the available science and discuss the next steps in pandemic and disease management and explore the best ways forward.

This conference is for those focused on the public health and clinical challenges of COVID-19, with an emphasis on seeking the best solutions among the uncertainty and promoting best practice in a fast-evolving emergency.

The Conference objectives are to:

​- Create an environment for knowledge sharing, collaboration and relationship building;

- Highlight activities that nationally-funded Centres of Research Excellence have undertaken that demonstrate collaboration across sectors and disciplines to achieve better health outcomes for Australians;

- Engage professionals across multiples sectors and disciplines in preventing, detecting, controlling and managing COVID-19;

- Provide guidance and insight into capacity building and strengthening knowledge, especially among high-risk populations;

- Provide conference delegates with new and innovative ideas that can be applied to local settings and systems to help create and improve health systems for local and diverse communities.
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