Today, hospitals and doctors use a system of about 18,000 codes to describe medical services in bills they send to insurers. Apparently, that doesn't allow for quite enough nuance.

The WHO, for instance, didn't see the need for 72 codes about injuries tied to birds. But American doctors whose patients run afoul of a duck, macaw, parrot, goose, turkey or chicken will be able to select from nine codes for each animal, notes George Alex, an official at the Advisory Board Co., a health-care research firm.

There are 312 animal codes in all, he says, compared to nine in the international version. There are separate codes for "bitten by turtle" and "struck by turtle."....