If I'm not mistaken, roundworms are one of the most common internal parasites, and usually won't take too long to treat. Just remember to dispose of his feces right away and keep him pooping in a different area than your other dogs.The vet should be able to sell you a preventative for your other pets... As far as your human family, just wash your hands a lot
(I have this weird phobia about me and/or my family getting worms lololol)