Sewer and grey tank valves are kept closed.
Dan, from your reply am I to assume that it is the hot water tank which is most likely the source of the bacteria.
Do we know how this bacteria affects humans and how to cure any symptoms
There are many thousands of different strains of bacteria, some beneficial, some harmful. For example, your gut is full of bacteria that your body needs.
But if the campground water, or a faucet has been contaminated with harmful bacteria, bleach should take care of it, along with the smell.
If the water smells like sulphur, even at your house, it's likely the water heater. But if you want, you can sanitize the entire water system by opening faucets while pumping in the bleach solution.
To sanitize the fresh tank is a little different as you'll have to set the 4 way valve to TANK and 'push' the solution into the tank, rather than use the Winterize/Sanitize setting. You can fill your water hose with bleach and use the campground water supply to push the hose contents into the fresh tank.