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Incubation and Contagious Periods of Infections

Young children get infectious diseases 10 to 15 times per year. As they get older, children get sick less often. This is because with each new infection their bodies build up antibodies that will defend the body if the same germ attacks in the future.

What is an incubation period?

The incubation period is the time between being exposed to a disease and when the symptoms start. If your child was around someone who is sick and the incubation time has gone by, then your child was probably not infected and won't get sick. It is also possible that your child's body had already developed antibodies to fight the infection.

What is the contagious period?

The contagious period is the amount of time during which a sick child can give the disease to others.

For major illnesses (such as hepatitis), a child will need to remain in isolation at home or in the hospital until all chance of spread has passed. For minor illnesses (like the common cold) the guidelines are less strict. Most health care providers would agree that a child should stay home at least until he feels well enough to return to school, and the fever has been gone for 12 hours.

What infections are not contagious?

Try not to become preoccupied with infections. Some of the more serious ones are not even contagious. Some infections are due to blockage of a passageway followed by an overgrowth of bacteria. Examples of these are ear infections, sinus infections, and urinary tract infections. Lymph node and bloodstream infections are also rarely contagious. Pneumonia is a complication of a viral respiratory infection in most cases and is usually not contagious. While exposure to meningitis requires consultation with your child's health care provider, most children exposed to this disease do not become infected. Venereal (genital) diseases are usually noncontagious unless there is sexual contact or shared bathing arrangements.

What are the guidelines for the common contagious infections?

Below is a chart that shows some common infections. It shows how long the incubation time is for each disease. This information should help you know when your child might get sick if he has been exposed to a disease. The chart also shows the amount of time your child will be contagious. Knowing this helps you know how long your child may need to stay home from school or child care.

  Disease             Period (days)    Contagious Period 

Chickenpox                10 to 21    5 days before rash 
                                      until all sores have 
                                      crusts (5-7 days) 

Fifth disease              4 to 14    7 days before rash 
  (Erythema infectiosum)              until rash begins 

Hand, foot, and mouth      3 to 6     Onset of mouth ulcers 
  disease                             until fever is gone 

Impetigo (strep or staph)  2 to 5     Onset of sores until 
                                      24 hours on antibiotic 

Lice                       7          Onset of itch until 
                                      one treatment 

Measles                    8 to 12    4 days before until 5 
                                      days after rash appears 

Roseola                    9 to 10    Onset of fever until 
                                      rash is gone (2 days) 

Rubella (German measles)  14 to 21    7 days before until 
                                      5 days after rash appears

Scabies                   30 to 45    Onset of rash until 
                                      one treatment 

Scarlet fever              3 to 6     Onset of fever or rash 
                                      until 24 hours on 

Shingles (contagious      14 to 16    Onset of rash until 
  for chickenpox)                     all sores have crusts 
                                      (7 days) (Note: No 
                                      need to isolate if 
                                      sores can be kept 

Warts                     30 to 180   See footnote A 

Bronchiolitis              4 to 6     Onset of cough until 
                                      7 days 

Colds                      2 to 5     Onset of runny nose 
                                      until fever is gone 

Cold sores (herpes)        2 to 12    See footnote B 

Coughs (viral)             2 to 5     Onset of cough until 
                                      fever is gone 

Croup (viral)              2 to 6     Onset of cough until 
                                      fever is gone 

Diphtheria                 2 to 5     Onset of sore throat 
                                      until 4 days on 

Influenza                  1 to 2     Onset of symptoms until 
                                      fever is gone 

Sore throat, strep         2 to 5     Onset of sore throat 
                                      until 24 hours on 

Sore throat, viral         2 to 5     Onset of sore throat 
                                      until fever is gone 

Tuberculosis               6 to 24    Until 2 weeks on 
                            months    drugs (Note: Most 
                                      childhood TB is not 

Whooping cough             7 to 10    Onset of runny nose 
                                      until 5 days on 

Diarrhea, bacterial         1 to 5    See footnote C 

Diarrhea, giardia           7 to 28   See footnote C 

Diarrhea, traveler's        1 to 6    See footnote C 

Diarrhea, viral (Rotavirus) 1 to 3    See footnote C 

Hepatitis A                14 to 50   2 weeks before until 
                                      1 week after jaundice 

Pinworms                   21 to 28   See footnote A 

Vomiting, viral             2 to 5    Until vomiting stops 


Infectious mononucleosis  30 to 50    Onset of fever until 
                                      fever is gone (7 days) 

Meningitis, bacterial      2 to 10    7 days before symptoms 
                                      until 24 hours on IV 
                                      antibiotics in 

Mumps                     12 to 25    5 days before swelling 
                                      until swelling gone 
                                      (7 days) 

Pinkeye without pus        1 to 5     See footnote A 

Pinkeye with pus           2 to 7     Onset of pus until 
  (bacterial)                         1 day on antibiotic 
                                      eye drops 


(A) Staying home is unnecessary because the infection is very mild and/or minimally contagious.

(B) Cold sores

  • Under age 6 years: Your child should stay home until the sores are dry (4 to 5 days). However, if the sores are on a part of the body that can be covered, your child does not need to stay home.
  • Over age 6 years: Your child does not need to stay home if he is beyond the touching, picking stage.

(C) Diarrhea

  • Not toilet trained: Your child should stay home until stools are formed.
  • Toilet trained: Your child should stay home until the fever is gone, diarrhea is mild, blood and mucus are gone, and your child has control over loose bowel movements.
  • Talk your child care provider about attendance restrictions.
Written by B.D. Schmitt, M.D., author of "Your Child's Health," Bantam Books.
Published by McKesson Provider Technologies.
Last modified: 2006-03-02
Last reviewed: 2006-03-02
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
Copyright 2006 McKesson Corporation and/or one of its subsidiaries. All Rights Reserved.
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