What is Covid-19 infection period? Study reveals new insights

A recent research on persons with moderate COVID-19 determines how long people are infectious and when they may safely be released from isolation.

Edited By Vertika Kanaujia (with inputs from ANI)
Updated19 Aug 2022
A health worker takes a swab sample from a woman to test for the Covid-19 coronavirus in the Huangpu district of Shanghai
A health worker takes a swab sample from a woman to test for the Covid-19 coronavirus in the Huangpu district of Shanghai(AFP)

Covid-19 virus has been changing its nature, symptoms and infection severity since it first hit the world. The recent surge in cases has new symptoms and severity which has led to 25% rise in cases and hospitalisation across the country. But for how long does the infection last in your body?

A recent research was conducted on 393 people out of which 57 persons had moderate COVID-19 infection at the start and comprised the final study population to state how long people are infectious and when they may safely be released from isolation.

The research, which is led by Imperial College London and published in The Lancet Respiratory Medicine journal, is the first to unveil how long infectiousness lasts for after natural COVID-19 infection in the community. After conducting detailed daily tests from when a patient was exposed along their Covid-19 infection journey it was concluded that less than a quarter of patients shed infectious virus even before symptom onset. It further adds, under a crude 5-day self-isolation period from symptom onset, two-thirds of cases released into the community would still be infectious, but with reduced infectious viral shedding. 

They also suggest that while lateral flow tests do not detect the start of infectiousness well, they more accurately identify when someone is no longer infectious and can safely leave isolation.

"Combining our results with what we know about the dynamics of Omicron infections, we believe that the duration of infectiousness we've observed is broadly generalisable to current SARS-CoV-2 variants, though their infectious window may be a bit shorter. Our evidence can be used to inform infection control policies and self-isolation guidance to help reduce the transmission of SARS-CoV-2," Study author, Professor Ajit Lalvani, Director of the NIHR Health Protection Research Unit in Respiratory Infections stated.

Co-author, Dr Seran Hakki also from Imperial's National Heart and Lung Institute, said, "If you test positive for COVID-19 or have symptoms after being in contact with someone with confirmed COVID-19, you should try to stay at home and minimise contact with other people."

The study presents most complete picture of the course of infectiousness to date

Previous studies estimating how long someone is infectious for have been a laboratory-based human challenge study or have used mathematical modelling.

The study found that the overall median amount of time that people were infectious was five days.

Though 24 out of 38 people tested positive on a PCR test before they developed symptoms of COVID-19 this does not indicate infectiousness and most people only became infectious after they developed symptoms. Only one in five participants were infectious before symptom onset (7 out of 35 cases).

Although levels of infectiousness reduced during the course of infection, 22 of 34 cases continued to shed infectious virus five days after symptoms began, and eight of these people continued to shed infectious virus at seven days.

When to end self-isolation after getting infected

To help understand when people may be able to safely leave isolation, the researchers compared levels of infectiousness with lateral flow test results.

Based on their findings, the researchers recommend that people with COVID-19 isolate for five days after symptoms begin, then complete lateral flow tests from the sixth day. If these tests are negative two days in a row, it is safe to leave isolation. If a person continues to test positive or do not have access to lateral flow devices, they should remain in isolation and, in order to minimise transmission to others, only leave on the 10th day after their symptoms began.

(With ANI inputs)

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