My first thought on flu and yellow fever was about this little known scientific fact.
https://www.eh-resources.org/volcanic-eruptions-and-european-history/
So, since Idaho has had a lot of earthquakes and no they are not "common" its also home to carbonated "soda springs" imma go with gassy. California too. The fires alone threw who knows what in air... Things melted that don't usually so maybe ait monitoring shoiluld be on peoples list.