Trip reports and other posts here on the forum by first-timers in Europe oftentimes mention trouble with not just crowding but with maintaining one's preferred sense of space, an issue that is even more sensitive with catching a bug on our minds.
When I was doing a group tour of the Vatican museums some years back the guide warned the group several times that it would be crowded, especially getting through the entrance, and he tried to diplomatically encourage / advise / coach attendees to be assertive and to huddle up -- it seemed like unnecessary pleading to me, having grown up in urban East Coast cities and having depended on subways and buses and school cafeterias and MLB games, but plead as he might, our group never made decent progress and getting through the turnstiles and security check took us forever ( I squirmed through with so much time to spare that I could use the WC and read the handouts before the group re-grouped)
DW News has been doing stories about a research institute that studies crowd management:
https://www.fz-juelich.de/ias/ias-7/EN/Research/Highlights/03_crowds_in_bottlenecks/_node.html
and I can't get over how blind they seem to be to the culturally determined nature of crowd behavior -- they mention how putting a pillar on a train station platform 'naturally' improves pedestrian traffic flow because of course everyone treats it like a roundabout.
As though roundabouts were part of nature! Or how everyone naturally keeps at roughly the same distance on a platform while waiting for a train to arrive -- try the same exercise in Madurai or Mexico City and see how that works out!
I guess I'm posting this because I still find myself surprised at how willfully blind even supposed experts are to the culturally conditioned qualities of our supposed natural preferences and behaviors. And it gives me yet another chance to recommend Joe Lurie's book on cross-cultural sensitivities :
https://www.perceptionanddeception.com
What travel memories stand out for you regarding things getting a little too close for comfort?