“..the pneumonic form is much more related to their lack of being seen by a medical professional than by some looming epidemic.”
But in the pneumonic form, it can spread quickly — and exponentially— from human to human, and can **cause** an epidemic.
One infected person sneezing in crowded quarters— say, in a transit terminal— can potentially infect many other travellers.
The general public and most doctors aren’t necessarily familiar with the disease. Its early symptoms can be mistaken for the flu.
And I’ll bet a large number of those types of patients would quickly overwhelm medical capabilities.