">https://twitter.com/johnestevens/status/1247060333967167489
According to The Times, he was put on oxygen last night (not a ventilator, but a mask):
https://www.thetimes.co.uk/edition/news/coronavirus-boris-johnson-taken-to-hospital-over-persistent-symptoms-b2xsbg9hs
"...
It was understood that he was driven to St Thomas’ Hospital, across the Thames from Westminster, at about 8pm, and given oxygen treatment.
...
Although Mr Johnson is not known to have any underlying health condition, he has struggled with his weight. In December 2018 he wrote in The Spectator that he weighed 16st 7lb. That would have put him in the obese body mass index category, which some studies suggest makes patients more susceptible to complications of coronavirus.
..."
I was concerned when he did not recover after seven days - from reading about cases it appears that most people recover after about a week, but that those who don't, often go on to develop more serious symptoms. I wish Boris all the best and hope he gets well as soon as is possible..