Scotland Secretary Michael Moore has been forced to postpone a key meeting with Alex Salmond over Scottish independence after falling victim to chickenpox.
A spokesman said the cabinet minister had cancelled his engagements and would now spend several days at home recovering from the highly-contagious illness.
Officials had initially insisted it was business as usual for Moore and that his diary had not been affected despite being struck down.
But his spokesman later said that he had been sent home and all his engagements, including Friday's talks with the First Minister, had been shelved.
Moore, who attended the weekly meeting of Prime Minister David Cameron's cabinet yesterday, was not aware until this morning that chickenpox was the cause.
The virus can spread through the air, in tiny droplets of saliva and mucus from an infected person, many days before the appearance of the tell-tale spots.
It can be picked up just by having a conversation or being in the same room as someone who has chickenpox for at least 15 minutes.
The NHS advises that adults with chickenpox should "stay off work until all the spots have crusted over" which can take up to six days from their first appearance.
Although most adults are immune after childhood cases, it is a common myth that you cannot get chicken pox twice - around one in eight sufferers report having had it previously.