Persistent shedding of COVID-19 – what does this mean?

Posted

16th March 2020

Blog

Several epidemiological studies have shown that the shedding of the SARS-CoV-2 virus that causes COVID-19 can continue for many days after symptoms resolve. What does this mean? Do people remain infectious after their symptoms resolve? The answer isn’t clear, but it seems that people are most infectious at the start of their symptoms, and much less infectious once they have resolved.

A few studies provide us with information on the shedding of the SARS-CoV-2 virus during COVID disease:

·       A small study of four healthcare workers in China found that PCR tests for virus remained positive for a couple of weeks after symptoms resolved.

·       Similarly, an epidemiological analysis of 18 patients with COVID in Singapore found that virus shedding was prolonged for 7 days or longer in 15 (83%) of the 18 patients.

·       A larger study of 191 patients in China found that the median duration of viral shedding was 20 days.

So does this mean that these patients remain infectious for as long as they continue to shed virus? No, we know from other diseases that this isn’t necessarily the case. Firstly, the detection of a virus by a PCR test isn’t the same as detecting a live virus; it could be detecting the “genetic shadow” of a resolved viral infection. Secondly, we know from epidemiological studies that respiratory viruses (such as influenza and SARS) are more transmissible when symptoms are present. Thirdly, shedding of respiratory (and other) viruses is known to continue sometimes long beyond symptoms have resolved.

Therefore, generally speaking, the advice is that the risk of transmission of respiratory viruses is considered to be low once symptoms have resolved (hence the recent change in the UK guidelines – that people with a continuous cough or fever should self-isolate for 7 days). However, it is worth remembering that shedding of the virus can continue after symptoms have resolved, reinforcing the need for continuous high levels of hand, respiratory, and environmental hygiene.

Share this article

Tags

Latest News

Blog
shutterstock_289471151.jpg

28 Australian Societies provide consensus on COVID…

Sourcing up-to-date reliable information on COVID-19 management a…

Blog
20.07.2020_Let’s not forget MRSA and the risk from contaminated surfaces-01-01 copy.jpg

Let’s not forget MRSA and the risk from contaminat…

There is strong evidence that MRSA transmission dynamics can incl…

Company news
08.07.2020-Hand-Wash-Game_GAMA_1366x472px.jpg

New digital hand hygiene game launches

Innovative educational game, ‘Hand Wash Squad’, helps children le…

Blog
29.06.2020-Risk-environmental-contamination-asymptomatic_GAMA_1366x472px.jpg

Environmental contamination risk from asymptomatic…

There is emerging evidence that contaminated surfaces play a role…

Blog
22.06.2020-DNA-marker_GAMA_1366x472px.jpg

Modelling the spread of SARS-CoV-2 from surfaces i…

The principle transmission route for the SARS-CoV-2 virus that ca…

Blog
12.06.2020-Face-Masks_GAMA_1366x472px.jpg

Face masks, face shields, and preventing the sprea…

Types of respiratory protection that is available, and where it s…

Blog
29.05.2020-hospital-transmission-COVID-19_GAMA_1366x472px.jpg

Assessing the risk of hospital transmission of COV…

As hospitals move past the peak of the COVID-19 pandemic, the ris…

Blog
RkyoZFjg.jpeg

Environmental contamination with COVID-19: how big…

There have been several studies examining the potential risk for …