Testing, tracing and mask-wearing can stop COVID-19 resurgences

Researchers in Australia, Denmark, and the United States conducted a study showing how community testing, contact tracing, and mask-wearing can lower transmission of Severe Coronavirus 2 (SARS-CoV-2) with acute respiratory syndrome in the state of New South Wales .

SARS-CoV-2 is the causative agent of the 2019 coronavirus disease (COVID-9) pandemic, which continues to sweep the world and pose an increasing threat to global health and the economy.

Robyn Stuart (Burnet Institute, Melbourne) and colleagues say the study indicates that community testing, tracking and wearing of masks can effectively control the spread of SARS-CoV-2 in community settings.

The results also suggest that of all the interventions considered, symptomatic testing, contact tracing, and contact testing are most important.

Adopting a multi-faceted strategy that combines testing, tracking, and wearing of masks in addition to adhering to hand hygiene and social distancing protocols is probably the most reliable way to ensure community-based transmission stays under control, the advises Team .

A pre-print version of the paper is available on the medRxiv * server while the article is being peer reviewed.

Calibration of the model for the NSW epidemic. Solid lines indicate the mean model projections over 20 model runs. shaded areas indicate 95% projected intervals over various initializations; Blue diamonds indicate data on confirmed locally acquired cases.

The spread of SARS-CoV-2 is unprecedented

With the first cases of COVID-19 first identified in Wuhan, China late last year, it quickly became clear that SARS-CoV-2 is spreading at an unprecedented and potentially exponential rate.

“As long as a significant part of the population remains susceptible to infection, the potential for new epidemic waves also exists in environments with a low number of active COVID-19 infections, unless adequate countermeasures have been taken,” write Stuart and colleagues.

Measures to contain the spread of the pandemic have already been very effective worldwide. In the second half of 2020, many governments decided to move from a rigorous crisis management approach to more casual strategies aimed at minimizing the risk of transmission while allowing previous social and economic activities to resume.

Estimated total infections from October 1 to December 31, 2020, assuming various test rates and mask intake assumptions, provided all community contacts can be tracked within a week with an average tracking time of 1 day.  Projections represent the median of 20 simulations.

Estimated total infections from October 1 to December 31, 2020, assuming various test rates and mask intake assumptions, provided all community contacts can be tracked within a week with an average tracking time of 1 day. Projections represent the median of 20 simulations.

When combined with hand hygiene and social distancing practices, community testing, contact tracing, and wearing masks can enable relatively high levels of mobility, the researchers say.

“Testing and contact tracing means that only those who are at greatest risk for transmitting the virus need to stay home, while masks mean people with undiagnosed infections are at lower risk to others,” they write.

Estimate how vulnerable New South Wales is to a new wave of epidemics

Now Stuart and colleagues have investigated the acceptance of these approaches in the Australian state of New South Wales. This setting has resulted in prolonged low transmission, non-universal mask use, high mobility and the use of a well-functioning test and tracking system.

Researchers set out to examine how vulnerable New South Wales could be to a resurgence in the spread of SARS-CoV-2 between October 1 and December 31, 2020, under various levels of testing, tracing and masking.

“In New South Wales, the use of masks in certain settings has been encouraged but not mandatory since July. At the same time, there was a strong focus on contact tracing, ”they write. “In this study, we look at a number of testing and contact tracking levels and assess the balance between masks, testing and contact tracking as a means of managing community-based transmission.”

What did the study find out?

The team found that wearing masks had the most significant relative effect on transmission when community testing and follow-up rates were lower and the least impact when testing and follow-up rates were higher.

With a very high testing rate – testing 90% of symptomatic people and 90% of known case contacts – the team estimated that the New South Wales epidemic would remain under control at least until late 2020 if it could be done quickly and quickly effective contact tracing is in place.

Assuming a very high testing rate, the team states that the estimated number of new cases between October 1 and December 31 under a high mask uptake scenario is only 70 to 110, compared to 340 to 1,400 under a scenario without Mask.

“However, when the test rates are lower, we estimate that the use of masks can play an important role in reducing the potential for epidemic recurrence,” say the researchers.

With a similar degree of mask wear and contact tracing, the number of new cases of infection in the same period would be up to six times higher if the test rate were to drop from 90% to 80%. 17 times higher when it fell to 65% and more than 100 times higher when it fell to 50%.

A multi-faceted strategy is likely to be the most robust

“Of the interventions considered, this study suggests that maintaining a high level of symptomatic testing, contact tracing, and contact testing is most important,” said Stuart and colleagues.

“Pursuing a strategy that combines aggressive testing, high mask usage, and effective contact tracing, as well as continued hygiene and distancing protocols, is probably the most robust means of controlling community-based transmission of SARS-CoV-2,” the respondents concluded.

* Important NOTE

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be considered conclusive, guide clinical practice / health-related behavior, or treated as established information.

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