Lawmakers were earlier told to stay away from Johnson’s weekly question time in parliament amid warnings that Westminster is a particularly infectious area.
Some 25 MPs, including a cabinet minister, are already thought to have isolated themselves.
“There’s a lot of COVID-19 in Westminster,” tweeted epidemiologist Professor Neil Ferguson, a government adviser, as he announced that he had also developed symptoms.
MPs will gather on Thursday however to debate new emergency legislation to deal with the coronavirus outbreak, which ministers hope to push through within days.
The government says its powers will only be used when “absolutely necessary” and the bill has support from opposition parties.
But some MPs voiced concern at the sweeping nature and duration of the proposals, and the effect on civil liberties.