What illness could wipe out an entire rat colont very quickly?

A gentleman is selling rat racks and states the reason he is selling the racks is due to an illness went through his rats and killed them all within weeks. Naturally, I want to run the other dang direction from these racks. However, I was curious what illnesses could do this. Anyone know what could do this to a rat colony (assuming they are being raised in a reasonably clean environment)? Thanks in advance!

SDA seems to be going around and can take it's toll on rats very quickly. While the disease itself is not deadly, it weakens the immune system to the point where secondary infections can come in and kill very quickly.
The good news is that the virus dies very quickly when there is no host for it to infect.
http://ratguide.com/health/viruses/sda.php


Sendai is another big one that works similarly to SDA, it weakens the immunes system and allows secondary infections to wipe out a colony very quickly. Sendai also dies very quickly when away from potential hosts.
http://ratguide.com/health/viruses/sendai_virus_sv.php