Human challenge study finds high viral shedding in asymptomatic people

The study first detected the virus in the throat and the nose two days before peak symptoms showed up

The Imperial College London has concluded the first study on 36 participants aged 18–29 years who were deliberately exposed to low dose of SARS-CoV-2 virus through the nose, and the various facets of infection were studied. All the volunteers had no previous infection or vaccination. In all, only 18 of 36 participants became infected, and the viral load in these people increased steeply before peaking on day five post-exposure.

Virus was first detected in the throat but the viral load increased to significantly higher levels in the nose than in the throat. Viral shedding began within two days of infection and the viral load increased to high levels and remained detectable for as long as 12 days after exposure to the virus. The results are posted as a preprint server Research Square. Preprints are yet to be peer-reviewed.

“This paper is the first of a series of deep analyses that this unprecedented consortium will produce. The manufacture of a Delta challenge agent is nearly complete,” immunologist Dr. Christopher Chiu from the Imperial College of London who led the team tweeted.