Infections: Incubation and Contagious Periods

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 stay 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 healthcare 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 healthcare provider, most children exposed to this disease do not become infected. Sexually transmitted diseases are usually not contagious 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.

                        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. If
                                      widespread blisters, until
                                      they are dry (7 days)

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

Meningitis                 3 to 6     Onset of symptoms and for
                                      1 to 2 weeks
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 (Seasonal)       1 to 3     Onset of symptoms until
                                      fever is gone over 24 hours

Influenza (H1N1)           4 to 6     Onset of symptoms until
                                      fever is gone over 24 hours 
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

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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.
• Talk your child care provider about attendance restrictions.