Challenge trial for Covid in England reveals airborne superspreaders

 Nature has a news story about a Lancet Microbe paper reporting the challenge trial. See links to and excerpts from both below.

Here's the Nature story:

What makes a COVID superspreader? Scientists learn more after deliberately infecting volunteers. A rigorous study identifies ‘supershedders’ who spew huge amounts of virus into the air — despite having only mild symptoms. by Saima Sidik

"A study of people who were intentionally infected with SARS-CoV-2 has provided a wealth of insights into viral transmission — showing, for example, that a select group of people are ‘supershedders’ who spew vastly more virus into the air than do others1.

"The publication describes data from a controversial ‘challenge study’, in which scientists deliberately infected volunteers with the virus that causes COVID-192. Although the approach drew opposition, the work has now yielded data on questions central to public health, such as whether the severity of symptoms correlates with how contagious people are and whether home COVID-19 tests can play a part in reducing viral spread.

...

"Challenge studies are “very bold”, says Gandhi. Some people argue that it’s unethical to give people an infection that can cause severe illness, but the research design comes with benefits. Challenge studies can substantially speed up vaccine testing, and they’re the only way to understand certain aspects of COVID-19, such as the stage before people test positive or develop symptoms.

"Researchers inoculated 34 healthy young participants by squirting a known quantity of viral particles up their noses. Eighteen developed infections and spent at least 14 days confined to hospital rooms. Each day, researchers measured viral levels in the participants’ noses and throats, in the air, and on the participants’ hands and various surfaces in the rooms.

...

"Of the 18 participants who developed infections, 2 shed 86% of the airborne virus detected over the course of the entire study — even though both had only mild symptoms. Previous research3 has provided evidence for the existence of superspreaders who infect large numbers of people. But whether such people are also ‘supershedders’ who emit copious amounts of virus, or simply have many social contacts, was up for debate

..

"None of the participants emitted a detectable level of virus into the air before testing positive, and only a small proportion of them left detectable virus on their hands, on surfaces or on masks that they donned temporarily.

"By the time they tested positive, most participants had already experienced mild symptoms, such as tiredness or muscle aches. That means that if people test as soon as they detect symptoms, rapid tests “can be a powerful tool” for controlling viral spread, says infectious-disease researcher Christopher Brooke at the University of Illinois at Urbana-Champaign.

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And here's the original paper:

Jie Zhou, Anika Singanayagam, Niluka Goonawardane, Maya Moshe, Fiachra P Sweeney, Ksenia Sukhova, Ben Killingley, Mariya Kalinova, Alex J Mann, Andrew P Catchpole, Michael R Barer, Neil M Ferguson, Christopher Chiu, Wendy S Barclay, Viral emissions into the air and environment after SARS-CoV-2 human challenge: a phase 1, open label, first-in-human study, The Lancet Microbe, 2023, ISSN 2666-5247, https://doi.org/10.1016/S2666-5247(23)00101-5. (https://www.sciencedirect.com/science/article/pii/S2666524723001015)

"After controlled experimental inoculation, the timing, extent, and routes of viral emissions was heterogeneous. We observed that a minority of participants were high airborne virus emitters, giving support to the notion of superspreading individuals or events. Our data implicates the nose as the most important source of emissions. Frequent self-testing coupled with isolation upon awareness of first symptoms could reduce onward transmissions."