Incubation period

An incubation period is the time it takes between the day a person is infected with a pathogen (something that causes a disease, like a virus), and the day that the person starts having symptoms of the disease. For example, if a person is infected with the common cold, it usually takes about one to three days for the person to start having cold symptoms. This means that the common cold's incubation period is one to three days.[1][2]

With some diseases, like Human Immunodeficiency Virus (HIV, the virus that causes AIDS), a person can still give other people HIV during the incubation period. Even though the person with HIV has no symptoms, the virus is making copies of itself during the incubation period.

What affects incubation periods

Many different things affect the incubation period for a disease. These things include:

  • How much of the pathogen a person got
  • Whether the person was vaccinated against this pathogen, and if they were, which vaccine was used
  • How fast the pathogen makes copies of itself once it is in the body
  • How strong the person's immune system is

Examples of incubation periods

Incubation periods are not exactly the same for everyone, because every person is different. Because of this, an incubation period is always written as a range (for example, "one to three days").

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

Some diseases have very short incubation periods. Other diseases have incubation periods of many years. For example:

Disease Incubation Period
Cholera 0.5 to 4 days[3]
Influenza (flu) 1 to 3 days[4]
Dengue fever 3 to 14 days[5]
Chicken pox 9 to 21 days[6]
HIV 2 to 3 weeks to months, or longer[7]
Rabies Usually 1 to 3 months, but can be less
than 1 week or more than 1 year[8]
Kuru disease 10.3 to 13.2 years (average)[9]


  1. Lessler J; Reich NG; et al. 2009. "Incubation periods of acute respiratory viral infections: A systematic review". The Lancet Infectious Diseases 9 (5): 291–300. doi:10.1016/S1473-3099(09)70069-6. PMC 4327893. PMID 19393959. 
  2. Common cold, The Mayo Clinic, Accessed 2012-05-28.
  3. Azman AS; Rudolph KE; et al. 2013. "The incubation period of cholera: A systematic review". Journal of Infection 66 (5): 432–8. doi:10.1016/j.jinf.2012.11.013. PMC 3677557. PMID 23201968. 
  4. Seasonal Influenza (Flu), Centers for Disease Control and Prevention, Accessed 2012-05-28.
  5. Gubler DJ 1998. "Dengue and dengue hemorrhagic fever". Clinical Microbiology Reviews 11 (3): 480–96. PMC 88892. PMID 9665979. 
  6. Chicken Pox, Medscape, accessed 2012-05-28.
  7. Kahn JO; Walker BD 1998. "Acute Human Immunodeficiency Virus Type 1 Infection". New England Journal of Medicine 339 (1): 33–9. doi:10.1056/NEJM199807023390107. PMID 9647878. 
  8. "WHO - Rabies". World Health Organization.
  9. Huillard d'Aignaux JN; Cousins SN; et al. 2002. "The incubation period of kuru". Epidemiology 13 (4): 402–8. doi:10.1097/00001648-200207000-00007. PMID 12094094.