I can certainly understand it being in the mains supply would be of great concern, though here thankfully our water utilities have at least in that regard a very good track record.It may be specific to the water supply within the place where we live, but it was cause for concern nevertheless and it could just as well apply to the water in the freshwater tank in the caravan.
I have no concerns here in the UK of drinking freshly, and directly drawn utility supplied water, on any bio contamination issue.
I have been involved in having utility water tested quite a bit. It's always been good, any issues have always been related to lack cleanliness with the faucets themselves, not the supply.
It is higher a risk in our caravans for several reasons, predominantly that the chorine used as a biocide would very quickly dissipate, added to that, wet surfaces being exposed to air and the higher temperatures could introduce and culture it. Personally I think the risk are low though the consequences very serious