Why a landmark study will help scientists grapple with the mysteries of Covid-19

Covid may have fallen off the agenda for some politicians, but scientists are still busy at work trying to better understand the infection.

Last year, a handful of brave volunteers willingly signed up to a government-funded study that deliberately exposed participants to the virus. The research has not been without its controversy, given the ethical considerations at play, but the first results have been shared with the public.

It’s provided a fascinating insight into the “beginning, middle and end” of a Covid-19 infection, chief investigator Professor Christopher Chiu said.

The scientists, from Imperial College London, determined that it typically takes two days for symptoms to start developing after exposure to the virus. An infection first appears in the throat and peaks after five days, at which point the virus is more abundant in the nose than the upper respiratory tract.

The study – the results of which have not yet been peer-reviewed – also found that lateral flow tests are highly effective at picking up the virus, with modelling suggesting having a test every three to four days will capture many cases, rising to 90 per cent with daily tests.

A total of 36 healthy and young participants with no immunity to Covid were exposed to a low dose of the virus and then closely monitored by medics in a controlled environment for 24 hours a day over a two-week period.

Out of the volunteers, 18 became infected, 16 of whom developed mild-to-moderate symptoms. None of the participants experienced serious symptoms.

Participants were only given a very small dose of the virus, the equivalent of less than one respiratory droplet if somebody was at the peak of their infection.

Yet those who were infected during the course of the study – regardless of whether they were symptomatic or not – went on to develop high viral loads.

“This shows the potential of the virus to replicate very, very quickly,” said Dr Andrew Catchpole, chief scientific officer at hVIVO, experts in human challenge trials.

The frightening speed at which Sars-CoV-2 replicates in our body goes some way to explaining how the pandemic took off in the way that it did. Confronted with the microscopic power of nature, humanity was helpless to fight back the initial waves of Covid that swept the globe.

It’s hoped the data gathered by the first-of-its-kind study will help in the development of antivirals, vaccines and diagnostics, providing scientists with a better idea of how the virus interacts with our bodies and the immune mechanisms that attempt to suppress infection.

The researchers are also continuing to assess why half of the study participants “resisted infection”.

Some of these individuals did show brief spikes in viral detection, before rapidly disappearing, but it remains unclear what immunological properties distinguished the infected group from the uninfected.

The scientists behind the study will continue to investigate this and attempt to get to the bottom of a mystery that has stumped some of the brightest minds since the beginning of the pandemic.