Full Version: Human challenge study findings
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A study in England (Imperial College, et al) exposed 36 young volunteers to COVID and watched the disease develop.

It was an early version of COVID (prior to Alpha).  Symptoms appeared within 2 days on average.  Initially it developed in the throat, but by 5 days was majorly in the nose.    
Half the volunteers got infected, 2 of which did not get symptoms.

Virus shedding was as high in the asymptomatic cases.

"Participants were exposed to the lowest possible dose of virus found to cause infection, roughly equivalent to the amount found in a single droplet of nasal fluid when participants were at their most infectious."

"Among the 18 infected participants, the average time from first exposure to the virus to viral detection and early symptoms (incubation period) was 42 hours, significantly shorter than existing estimates"

"These levels peaked at around five days into infection on average, but high levels of viable (infectious) virus were still picked up in lab tests up to nine days after inoculation on average, and up to a maximum of 12 days for some, supporting the isolation periods advocated in most guidelines."  
(The isolation periods havebeen reduced to 5 days by the CDC.  That's post-symptom, so about 7 days post-infection)

"While the virus was detected first in the throat, significantly earlier than in the nose (40 hours in the throat compared to 58 hours in the nose), levels were lower and peaked sooner in the throat."
interesting study, particularly incubation period and duration of infectious shedding.   

confirmation of infectiousness from asymptomatic but infected person seems consistent with other studies/sources.
I do wish the CDC will shorten quarantine time (exposed, but test negative) and lengthen isolation time (infected).

The other big surprise to me was that only 2 of 18 that got infected were asymptomatic. It does mean 11% of those infected might not realize they are contagious to others, and could spread the virus.

I guess one other thing is not just that they were shedding virus, but were they shedding it in ways that could get others sick? Someone with the symptom of a cough seems much more likely to infect others than an asymptomatic case with the same viral shedding but no cough.