Health minister and AM for Cardiff South and Penarth, Vaughan Gething, has announced that he is self-isolating for 14 days after his son exhibited symptoms of Covid-19.
"My son as a new wheezy cough," he said in a Twitter video.
"So, I'm not going to be in the Assembly for the foreseeable. I'm following the advice we're asking the public to follow as well.
"The objective in all the advice we're giving is to delay the spread of coronavirus and to give our Health Service the opportunity to help save more lives.
"Take care of yourselves and help take care of each other."
Mr Gething was due to be making a statement on the country's response to coronavirus in the Senedd on Tuesday.
Four other AMs say they are in self-isolation.
Mr Gething's decision comes after an announcement by the prime minister that those who exhibit symptoms of the Coronavirus, including a new or persistent cough, should self-isolate along with everyone else in their household for a period of two weeks.
The extreme measures are intended to suppress the epidemic so that the NHS does not become overwhelmed.
The policy announcement will trigger an unprecedented change to daily life as the country's quarantine measures are intensified and people are told to avoid all non-essential social movement.
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