The Welsh Conservative leader is taking a break from politics to recover from mental health issues.
Andrew RT Davies says he's been fighting a dose of the flu, and subsequently, COVID, over the past fortnight.
Paul Davies, who stood down as the Tories' leader in January, will take over as the party's acting leader in the Senedd.
In a statement on social media, he said illness has ''knocked me for six and had a troubling impact on my mental well-being'', although he was starting to recover.
Mr RT Davies, a South Wales Central MS, is also a county councillor for Rhoose.
This week, he was absent from both the Senedd in Cardiff Bay and the Conservative party conference in Manchester.
He added: ''Like many men, I’ve always believed I had a shield of invincibility, and like many who have struggled, I’ve contemplated whether I should make this public.''
''However, as a leader, I believe you should set an example and I want to be open and honest - in the good times and the bad - as I know many people have struggled and will do with their mental health.''
''As such, and on doctor’s orders, I will be taking a complete break from work to ensure I can fully recover and bounce back from the difficulties I’ve experienced over the past fortnight.''
Mr RT Davies, originally from Cowbridge, has been a regional MS since 2007 - four years later, he was elected as Welsh Conservatives leader for the first time.
He resigned in 2018, but returned to the role at the start of this year.
Since February 2019, Mr RT Davies has also served as a county councillor, after winning a by-election in Rhoose, amid a campaign to save Llancarfan Primary School from closure.
Last year, he was made a CBE in the New Year Honours list for political and public service.
In January, Paul Davies, the MS for Preseli Pembrokeshire, resigned as leader, after he was seen drinking with other politicians - days into a COVID-related ban on serving alcohol in licensed premises.