Are there food safety issues with sous-vide cooking?
If you do it properly, no there are no health issues.

A combination of two things are required to kill beasties: heat and time. The higher the heat you expose them to, the faster they die. Generally any temperature above 130 F is enough to kill most beasties, it just requires a significantly larger amount of time compared to a higher temperature.

I go into a lot of detail regarding Salmonella in this answer of mine:

Is it safe to eat a cooked steak that (briefly) touched the plate that was holding the raw meat?

I have several tables there to show exact timings, etc.

If you think I should copy/paste that here, then let me know in a comment