There exists a Health Department rule in some states that prohibits parrots from entering certain health care facilities. However, dogs, cats, and llamas are permitted on those premises, but not those nasty parrots.
Those filthy mammalian visitors can carry many different insects, worms, bacteria (and worse) which can attack the human body. As far as I know, other than pulmonary chlamydiosis (“Parrot Fever”), there are only five diseases or afflictions which can be transferred from parrots to humans:
PEROT FEVER: Marked by up to a 40% loss of height; enlargement of the ears; a squeaky, grating voice; paranoia; a strong desire to repeatedly run and retreat; and occasionally a giant sucking sound.
SONIC SHOCK SYNDROME: Primarily marked by a piercing scream with upper harmonics which only dogs and whales can hear. Can also include any or all of the following: insane cackling immediately after performance of a prank or “bad thing”; repeated vocalizations of noises which resemble human intestinal distress or reproductive activity; mumbling conversations which can almost be deciphered; repetition of one side of a phone conversation; and the utterance of X-rated phrases in the presence of house guests and children.
MACAW FOOD-WASTING DISEASE: This affliction, while attributed to macaws, can be caught from all known members of the Psittacine family. The disease primarily manifests itself in humans by the behavior of tossing food away from the table in apparent disdain, followed later by consumption of the food from the floor, wall, ceiling, clothing, windows, or whatever surface it adhered to. Other symptoms include stuffing food items into armpits or pockets for later eating; mixing pieces of food with drinking water to make a gelid, soupy, mass; eating only one form of food to the exclusion of all others; eating only the food that is found on other people’s plates; regurgitating food for loved ones; and eating feces just because it’s there.
AVIANASTICS: Usually indicated by the ability to contort the body in the same way as parrots. Sufferers are frequently found clinging to the ceiling near a corner, with their torso twisted horizontally back between their legs, though other body movements and contortions include: hanging upside down from light fixtures while swinging in a rapid figure-eight motion; clinging to adjacent walls with legs at more than a 240-degree angle; and pressing the posterior against a window and pooping for distance.
CHIRPEES: Primarily indicated by an itch in the credit card or checkbook which then progresses to the collection of at least one of each species of Psittacine. Secondary symptoms include repetitive purchases of bird toys; purchase of bird food in boxcar loads; a wallet the size of Detroit to contain pictures of the birds; insane avian naming conventions (“This is my bird Squeeeeeee, and my other bird Foofie, and my other bird Bumpertribblebibbet of Bree, and my other bird Ookie Wookums Bappy Pie.”); and active participation in every known Internet bird newsgroup and mailing list, which includes the little-known alt.compulsion.birds.birds.birds, rec.pets.birds.more, HELLOHELLOHELLO-L, and MASTERBIRDER-L. Birthday Bird