About two out of three patients with COVID-19 (65%) continue to transmit it. coronavirus, i.e. being contagious five days after the onset of their symptoms, while one in four (24%) seven days after the onset of symptoms, albeit with a now reduced viral load, shows the most comprehensive study of this kind conducted by the British. scientists. The average duration of contagiousness is five days.

It has also been found that only one in five is contagious before the onset of symptoms (cough, fever, loss of taste/smell, sore throat, muscle aches, headache, loss of appetite, etc.). The study also found that the onset of symptoms occurs an average of three days before peak viral load.

The study also concluded that so-called lateral tests or rapid antigen tests are less accurate in the early days of infection, producing false negative results in about a third of cases (their accuracy is 67% in the initial phase of the disease). Instead, they are much more accurate (92%) in determining whether someone is no longer contagious at the end of the illness, so they can stop isolating them.

Researchers from Imperial College London, who published a related publication in The Lancet Respiratory Medicine, studied 57 people using daily coronavirus tests and questionnaires before, during and after being diagnosed with COVID-19 infection. Viral load assessment has been considered a key indicator of infectivity and transmissibility. The aim of the study was to pinpoint the beginning and end of the period when a person with coronavirus can transmit it to others.

In many countries, health authorities are now recommending that when someone is diagnosed with coronavirus, they self-isolate for five days and then avoid contact with people vulnerable to COVID-19 (e.g. elderly, immunocompromised, etc.) for another five days. .). . . ).

Following their findings, the researchers recommend that people with coronavirus self-isolate for five days after the onset of the first symptoms and take a rapid test (rapid) starting from the sixth day. If they have two negative tests in a row (rather than one), then they can safely stop being isolated. If rapid tests continue to be positive, or if they do not have such tests to self-check, then they should remain in isolation for as long as the test is positive, although they may come out of isolation on the tenth day after the onset of symptoms, but with caution for others .

“The new study undeniably shows that people shed infectious virus for much longer than five days,” virologist Stephen Griffin of the University of Leeds in Britain told New Scientist.

But the study was conducted in 2020-21, when the Omicron variant (which generally has a lower viral load according to other studies) had not yet become dominant, but was circulating mainly Alpha and Delta.

Susan Hopkins of the British Health Security Agency said current recommendations for a five-day lockdown are still being reviewed. “We know that most transmission in adults occurs from three days before symptom onset to five days after, and also that Omicron’s virulence peaks in a shorter time period than with previous variants.”

^{Source: RES-IPE}