XBB has been floating around at fairly constant low levels here in MA for months & months. Now, as cases are surging, XBB is becoming dominant.

I’m seeing people interpreting this as XBB causing the surge, but disease transmission is stochastic & I’m starting to suspect that at we’re seeing may instead be a founder effect — i.e., the *surge* is causing the predominance if XBB, b/c any surge must end up with some variant being dominant.

Curious to hear what others think about this!