Medical Advice >> Pediatric Advisor

Young children are afflicted with infectious diseases 10 to 15 times per year. The attack rate decreases with age because with each new infection we build up antibodies against future ones.

What is an incubation period?

The incubation period is defined as the time between exposure to a contagious disease and the onset of symptoms. This information should help answer the questions, "When will my child come down with it?" and, "Should we cancel our weekend plans?"

If the outer time limit of the incubation period passes and your child is still well, he or she has probably escaped that infection for now (or has previous antibodies against it).

What is the contagious period?

The contagious period is defined as that amount of time during which a sick child's disease is contagious to others. Knowing this helps answer the question, "How long does my child have to stay home from school or day care?"

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 physicians 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 physician, 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?

 
                        Incubation 
  Disease             Period (days)    Contagious Period 
---------------------------------------------------------------
---------------------------------------------------------------
SKIN INFECTIONS 

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 
                                      antibiotic 

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 
                                      covered.) 

Warts                     30 to 180   See footnote A 

---------------------------------------------------------------
RESPIRATORY INFECTIONS 
 
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 
                                      antibiotic 

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 
                                      antibiotic 

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 
                                      contagious.) 

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

---------------------------------------------------------------
INTESTINAL INFECTIONS 
 
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 
                                      begins

Pinworms                   21 to 28   See footnote A 

Vomiting, viral             2 to 5    Until vomiting stops 

---------------------------------------------------------------
OTHER INFECTIONS 

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 
                                      hospital 

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

Pinkeye without pus        1 to 5     See footnote A 
  (viral) 

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

TABLE FOOTNOTES

(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.
• Consult your day care provider about attendance restrictions.

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.