Incubation and Contagious Periods of Infections

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.

SKIN INFECTIONS
Disease	Period (days)	Contagious Period
Chickenpox	10 to 21	5 days before rash until all sores have crusts (5-7 days)
Fifth disease (Erythema infectiosum)	4 to 14	7 days before rash until rash begins
Hand, foot, and mouth disease	3 to 6	Onset of mouth ulcers 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 for chickenpox)	14 to 16	Onset of rash until 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
Disease	Period (days)	Contagious Period
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
Disease	Period (days)	Contagious Period
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
Disease	Period (days)	Contagious Period
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 (viral)	1 to 5	See footnote A
Pinkeye with pus (bacterial)	2 to 7	Onset of pus until 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. Talk your child care provider about attendance restrictions.