Add aria-live="polite"
and role="region"
to the container where your content changes in.
Using JavaScript, it is possible to dynamically change parts of a page without requiring the entire page to reload — for instance, to update a list of search results on the fly, or to display a discreet alert or notification which does not require user interaction. While these changes are usually visually apparent to users who can see the page, they may not be obvious to users of assistive technologies. ARIA live regions fill this gap and provide a way to programmatically expose dynamic content changes in a way that can be announced by assistive technologies.
With the region
role you signify the importance of the element. And with aria-live="polite"
you notify the user, but without interrupting whatever the screenreader is saying at the moment.
<div role="region" aria-live="polite">
// User is notified when the content changes here.
</div>
For more information check MDN - aria-live MDN - role-region