Incubation period is the time elapsed between exposure to a pathogenic organism, or chemical or radiation, and when symptoms and signs are first apparent. The period may be as short as minutes to as long as thirty years in the case of variant Creutzfeldt-Jakob disease.

While Latent or Latency period may be synonymous, a distinction is sometimes made between Incubation period, the period between infection and clinical onset of the disease, and Latent period, the time from infection to infectiousness. Which is shorter depends on the disease.

A person may be a carrier of a disease, such as Streptococcus in the throat without exhibiting any symptoms. Depending on the disease, the person may or may not be contagious during the incubation period.

Examples of incubation periods

Incubation periods can vary greatly, and are generally expressed as a range. When possible, it is best to express the mean and the 10th and 90th percentiles, though this information is not always available. The values below are arranged roughly in ascending order by number of days, although in some cases the mean had to be inferred.

For many conditions, incubation periods are longer in adults than they are in children or infants.

Disease	Incubation period	Reference
Cellulitis caused by Pasteurella multocida	less than 1 day
Cholera	1-3 days
Influenza	1-4 days
Scarlet fever	1-4 days
Common cold	2-5 days
Ebola	2-21 days
Rocky Mountain spotted fever	2-14 days
SARS	up to 10 days
Roseola	5-15 days
Polio	7-14 days
Pertussis	7-14 days
Measles	9-12 days
Smallpox	7-17 days
Generalized tetanus	7-21 days
Chicken pox	14-16 days
Erythema infectiosum (Fifth Disease)	13-18 days
Mumps	14-18 days
Rubella (German measles)	14-21 days
Infectious mononucleosis	28-42 days
Kuru	mean between 10.3 and 13.2 years

See also

• Quarantine
• Prodrome