A new study of people with mild Covid-19 symptoms has revealed how long people are infectious for and when they can leave isolation.
The study analysed 57 people with Covid-19 and conducted daily tests from when the patient was first exposed to SARS-CoV-2 in order to identify how much of the virus they were transferring to others.
The research, which was funded by the National Institute for Health and Care Research (NIHR) and led by Imperial College London, found that people with Covid-19 are not infectious before their symptoms start to develop and has become the first ever study to indicate how long contagiousness lasts for after the initial infection.
The study indicated that two thirds of the patients were still infectious five after their symptoms began. The research also suggested that whilst lateral flow tests don’t detect the start of infectiousness particularly well, they are a good way of determining when somebody is no longer at risk of passing the virus onto others and can therefore leave isolation.
Study author, Professor Ajit Lalvani, who is the 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.”
In light of their discoveries, the researchers are now recommending that those infected with Covid-19 should isolate for five days after their initial symptoms first start and should move onto lateral flow tests on the sixth day.
If lateral flow tests come up negative for two days in a row, researchers say it is safe to then leave isolation – if the tests are positive, individuals should remain in isolation but can come out 10 days after their symptoms first began.
Current NHS guidelines state that people should stay at home in isolation for just five days.
