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Incubation and Contagious Periods of Infections
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
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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
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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
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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
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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
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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.
