So the Babylon Bee tweets that Trump is building a Coronavirus-proof wall, and some guy tweets about a YouTube video of viruses climbing "tiny little ladders:

BREAKING: YouTube Video Shows Coronavirus Using Tiny Ladder To Scale Trump's Wall https://t.co/6b1GtvtnqN — Elvis Trump (@Elvis_Trump) March 5, 2020

Here's something I wrote (under the heading of Mexican Flu And Little Tiny Backpacks) during the 2009 flu pandemic in Mexico, which of course crossed into the US because no one tried to stop it:

Viruses need hosts, and stopping people coming stops the virus coming.