Back in the early days of COVID-19, @BPC_Bipartisan's @johncfortier1, continuity of government expert, wrote about what could happen if the president were to get sick. A series of blogs: https://bipartisanpolicy.org/blog/what-happens-to-congress-the-president-and-the-courts-during-a-crisis-like-coronavirus-or-9-11/

https://bipartisanpolicy.org/blog/the-25th-amendment-what-if-the-president-gets-covid-19/

https://bipartisanpolicy.org/blog/continuity-of-government-presidential-succession/

https://bipartisanpolicy.org/blog/continuity-of-government-what-is-the-presidential-succession-act/

https://bipartisanpolicy.org/blog/continuity-of-government-boris-johnson-and-presidential-succession/

Some key points: back in April British PM Boris Johnson fell extremely ill. "...the prime minister’s illness and the relatively smooth temporary transfer of power highlight a glaring weaknesses in our own system of presidential succession." https://bipartisanpolicy.org/blog/continuity-of-government-boris-johnson-and-presidential-succession/

@BPC_Bipartisan's @johncfortier1 raises important questions about whether the current Presidential Succession Act is constitutional, and points out that if the president and vice president are sick, we might be in for a world of trouble: https://bipartisanpolicy.org/blog/continuity-of-government-what-is-the-presidential-succession-act/