Written by: Dr. Jacquie Jacob, University of Kentucky

Acute: An acute disease typically involves a sudden onset of severe clinical signs and death (in contrast with a chronic illness, which involves long-term or recurrent symptoms).

Chronic: A chronic disease generally progresses slowly and/or involves long-term or recurrent symptoms (in contrast with an acute illness, which involves a sudden onset of symptoms).

Contagious: A contagious disease spreads rapidly from one individual to another (in contrast with a noncontagious disease, which does not spread easily).

Infectious: Infectious diseases are caused by organisms, such as bacteria, viruses, fungi, and parasites, that infect, or invade, another organism and cause disease.

Morbidity: The term morbidity refers to the number of birds within a given flock that are affected by a certain condition or disease (disease prevalence within a population) and that need to be culled— for health reasons such as leg problems or other clinical signs of disease—as a result.

Mortality: The term mortality refers to the number of birds that die from an illness within a given flock.

Noncontagious: A noncontagious disease typically does not spread easily from individual to individual (in contrast with a contagious disease, which spreads easily).

Noninfectious: Noninfectious diseases are caused by nonliving agents such as poisons, mycotoxins, and nutritional deficits.

Poultry: The term poultry refers to chickens, turkeys, ducks, geese, quail, pheasants, pigeon, guinea fowl, peafowl, ostrich, emu, and rhea.