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.Common cold, The Mayo Clinic, mayoclinic.com. Accessed 2012-05-28.

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 Influenza (flu) 1 to 3 daysSeasonal Influenza (Flu), Centers for Disease Control and Prevention, cdc.gov. Accessed 2012-05-28.Dengue fever  3 to 14 days Chicken pox 9 to 21 daysChicken Pox, Medscape, accessed 2012-05-28. HIV 2 to 3 weeks to months, or longer Rabies Usually 1 to 3 months, but can be lessthan 1 week or more than 1 year Kuru disease 10.3 to 13.2 years (average)

References

Category:Diseases
Category:Epidemiology