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Edinburgh Live
Edinburgh Live
National
Nina Massey, PA Science Correspondent & Sophie Buchan

People with mild Covid likely to be infectious for five days, new study suggests

According to a new study, it has been suggested that people with 'mild' symptoms of Covid could be infectious for an average of five days.

According to the research, published in The Lancet Respiratory Medicine journal, one in five people in the study were infectious before symptoms started, it was suggested.

In addition to this, two-thirds of cases were still infectious five days after symptoms began, with a quarter still infectious at seven days.

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Detailed daily tests were conducted from when people were exposed to the virus to look at how much virus they were shedding throughout their infection with the study, led by Imperial College London, said to be the first to reveal just how long the infectious period lasts within the community after contracting the virus.

The findings indicate that lateral flow tests (LFT) do not reliably detect the start of infectiousness however they can still be used to safely shorten self-isolation. Because of the findings, researchers are recommending that those with the virus isolate for five days after symptoms begin and do lateral flow tests from the sixth day.

If the tests are negative two days in a row, it is safe to leave isolation however if someone continues to test positive, they should isolate while testing positive but may leave isolation 10 days after their symptoms began.

Study author, Professor Ajit Lalvani, director of the NIHR Health Protection Research Unit in Respiratory Infections at Imperial, said: "Before this study we were missing half of the picture about infectiousness, because it’s hard to know when people are first exposed to SARS-CoV-2 and when they first become infectious.

"By using special daily tests to measure infectious virus (not just PCR) and daily symptom records, we were able to define the window in which people are infectious. This is fundamental to controlling any pandemic and has not been previously defined for any respiratory infection in the community."

He added: "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."

The new study followed people who were exposed to someone with PCR-confirmed Covid in their home between September 2020 and March 2021 and May to October 2021, including some who were vaccinated and others who were not.

Samples from a total of 57 people were used, but the duration of infectiousness was only measured in 42 people. There were 38 people with a confirmed date of when their symptoms started and three were asymptomatic.

Professor Lalvani said: “Self-isolation is not necessary by law, but people who want to isolate need clear guidance on what to do. The NHS currently advises that if you test positive for Covid-19 you should try to stay at home and avoid contact with other people for five days, but our data suggest that under a crude five-day self-isolation period two-thirds of cases released into the community would still be infectious – though their level of infectiousness would have substantially reduced compared to earlier in the course of their infection.”

He continued: “Our study finds that infectiousness usually begins soon after you develop Covid-19 symptoms. We recommend that anyone who has been exposed to the virus and has symptoms isolates for five days, then uses daily lateral flow tests to safely leave isolation when two consecutive daily tests are negative.”

Covid symptoms in children, according to the NHS

Symptoms of COVID-19 can include:

  • A high temperature or shivering (chills) – a high temperature means you feel hot to touch on your chest or back (you do not need to measure your temperature)
  • A new, continuous cough – this means coughing a lot for more than an hour, or 3 or more coughing episodes in 24 hours
  • A loss or change to your sense of smell or taste
  • Shortness of breath
  • Feeling tired or exhausted
  • An aching body
  • A headache
  • A sore throat
  • A blocked or runny nose
  • Loss of appetite
  • Diarrhoea
  • Feeling sick or being sick

Covid symptoms in adults, according to the NHS

Symptoms of coronavirus (COVID-19) in adults can include:

  • A high temperature or shivering (chills) – a high temperature means you feel hot to touch on your chest or back (you do not need to measure your temperature)
  • A new, continuous cough – this means coughing a lot for more than an hour, or 3 or more coughing episodes in 24 hours
  • A loss or change to your sense of smell or taste
  • Shortness of breath
  • Feeling tired or exhausted
  • An aching body
  • A headache
  • A sore throat
  • A blocked or runny nose
  • Loss of appetite
  • Diarrhoea
  • Feeling sick or being sick

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