Suggestions for zombie virus

I’m running a modern day zombie apocalypse setting using 3.5 as a base. The players are playing themselves. One is a neuroscientist IRL and he correctly suspects the virus is spreading through the public water system. another player is a civil engineer and said water treatment plants have on site labs for testing. So the players decided to go to the water treatment plant so they can run some tests.

I was not prepared for this so early and thought I’d have time to flesh out how the virus works. Well now I have damn irl scientist about to run labs on the virus I know nothing about.

Can anyone shed some light on what my players might uncover in the lab testing the water?

All I had prepared was that the virus was spreading through the water system.

Thanks!