They're really nasty bacteria and once in a system they are hard to get rid of because then you have to heat everything to temperatures that the system normally might never reach.

That's why central heating systems that run 'low' every now and then stoke up to 60 degrees or more on the secondary circuit for tap water.

And data centers are the perfect location, endless 35 to 45 degree water. Cooling towers are the main problem for this, another is aerosols of water that has been sitting in the sun for a while, for instance in a garden hose exposed to the sun.