GENEVA—Officials from the World Health Organization remain relatively unconcerned by the rise in cases of bird arthritis, a degenerative joint disease found in birds. "We are aware of the existence of avian osteoarthritis, but have chosen to focus on more immediate threats," WHO Director-General Lee Jong-wook said Monday, after several common teals were found doddering about a pond in southern Wales. "Most severely infected birds are too creaky and stiff to spread the disease very far." Experts say this is the least alarming public-health risk since the 1953 breakout of swine bursitis.