Every single one of the people infected by COVID has been contaminated by someone around them.
(It wasn't true of the plague during the great pandemics, as it was also borne by rats and their poop)
Perhaps the Russian military is overreacting with the blanket quarantines, but the odds are more likely that they understand the nature better than anyone else.
Again, normal pneumonic plague approaches 100% fatality rates. This is potentially a weaponized form.
This is an "oh, fuck" moment.
The reason we've haven't had more outbreaks of more diseases in the last century is because we had a lot of smart vigilant well-resourced people who very much felt the disease was the problem, and took steps to mitigate.
Classic late-stage civilization blunder is taking the fruits of civilization for granted. Sorry you're not aware of those things, but that's on you.