Isolation period of an infection is impoant to control its spread. What is TRUE about isolation period of enteric fever?

Since typhoid fever is infectious and has a prolonged course, the cases are better transferred to a hospital for proper treatment, as well as to prevent the spread of infection. As a rule, cases should be isolated till three bacteriologically negative stools and urine repos, are obtained on three separate days. Ref: Park's Textbook of Preventive and Social medicine, 19th edition, Page 196.