Chickens can pass disease to humans. In particular, the transmission of avian flu and bacteria are of great concern. Live chickens can pass avian flu to humans and bacterial infections can be transmitted through contact with the birds. Staph infections and food poisoning can be contracted if proper food handling procedures are not followed. Properly cooking chicken removes part of the risk but it does not remove all risk. Care should be used when in contact with chickens.
Staphylococcus Aureus
Commonly referred to as a staph infection, staphylococcus aureus can be transmitted from raw chicken to humans as well as from live chickens to humans. Once staphylococcus aureus is contracted, humans can spread it to other humans as it is highly contagious.
Avian Flu
Colorized electron microscope view of H5N1 virusThis is a serious viral infection that has many people worried. Some medical professionals feel that avian flu will be the next flu pandemic. There are two strains of avian flu of particular concern. Both H7N7 and H5N1 are proven to pass from poultry to humans. The first was noted in an outbreak back in 1997 in The Netherlands. Almost 100 individuals became infected with this virus as a result of direct contact with chickens and poultry. The H5N1 is more recent. First identified in 2004, it remains a worldwide concern.
Chicken mites (red mites, bird mites) suck blood from chicken and other birds. They don't much care for humans, but they will bite and a lot of people will get an itchy rash from them. They also will infest cats and dogs.
They are not known as disease vectors, but are capable of carrying the virus for St. Louis encephalitis, and can pass Salmonella species from bird to bird.