In May 1998 Hussein, a heavy smoker, was admitted to the Mayo Clinic, but doctors were unable to diagnose his ailment. Hussein returned to the clinic in July after suffering severe fevers; doctors then diagnosed him with Non-Hodgkin lymphoma. He stayed in the clinic until the end of 1998, while his brother Hassan, who had been crown prince since 1965, acted as regent. He was given six courses of chemotherapy for his lymph gland cancer over a five-month period. Hussein gained the respect of the Mayo Clinic staff for his warmth and kindness; on one occasion, a janitor cried uncontrollably after Hussein prepared a birthday party for her in his suite.