Doctors are often asked about incubation times for the common childhood infections, so that they can advise whether the child should go to school etc. Incubation time is the time between coming into contact with the source of the infection and symptoms showing. Infectivity is the length of time that you are infectious. Both of these can be variable, so the following is only a guide. There is a slightly fuller list at HPA guidance.
Note: * indicates a notifiable disease. These are required (by law) to be reported to government authorities.
|8-10 days||6-16 days||48 hours from last episode of diarrhoea or vomiting.||Exclude for 48 hours longer in children who are unable to maintain good personal hygiene.|
|Chickenpox||11-20 days||Up to 4 days before (usually only 1 day) to 5 days after.|
Cases often transmit before appearance of rash.
|5 days from the onset of rash.||Traditionally excluded until all lesions are crusted but no transmission recorded after day 5.|
Contacts with a weak immune system need prevention.
|Campylobacter||1-11 days||Patients probably not infectious if treated and diarrhoea has resolved.||48 hours from last episode of diarrhoea.||Exclude for 48 hours longer in children who are unable to maintain good personal hygiene.|
Mean = 8
|While active (direct contact).|
Infective up to 2 weeks.
|None||Transmission more likely in young children by direct contact - very few data.|
|13-18 days||30% in families|
10-60% in schools
|None||Avoid infection in pregnant women and people with a weak immune system.|
|Glandular fever||33-49 days||At least 2 months||None||None|
|Hand, foot and mouth disease||3-5 days||Up to 50% in homes and nurseries.||None||Stool excretion continues for some weeks. Avoid infection in pregnant women.|
|Head lice||n/a||While harbouring lice.||None||Note need for treatment of cases and contacts shown to have head lice.|
|Hepatitis A||15-50 days||From 2 weeks before to 1-2 weeks after jaundice onset.||Exclude until 7 days after onset of jaundice (or 7 days after symptom onset if no jaundice).||Good hygiene needs emphasising.|
|Herpes simplex virus|
|1-6 days||While lesions are moist.||None||Highly infectious, especially amongst young children.|
|Impetigo||Skin carriage 2-33 days before development of impetigo (streptococci)||High (streptococci)|
(Variable infectivity depending on causative bacteria.)
|Until lesions healed or crusted or 48 hours after starting antibiotic treatment.||None|
|Measles*||6-19 days||Highly contagious in non-immune population.|
A few days before to 6-18 days after onset of rash.
|4 days from onset of rash.||Check immunisation.|
Risk of serious infection in people with a weak immune system (give preventative treatment).
|Mumps*||15-24 days||10-29 days.|
Moderately infective in non-immunised population.
|5 days from onset of swelling.||Outbreaks reported in vaccinated secondary school children.|
|Ringworm||Varies||Until lesions resolve.||Exclusion not usually required.||Good hygiene helps.|
|Rubella*||13-20 days||1 week before to approximately 4 days after onset of rash.||6 days from onset of rash.||Check all female contacts are immune.|
|Scabies||Varies||Until mites and eggs are dead.||Can return after first treatment.||Risk of transmission is low in schools but outbreaks do occur.|
Close contacts should also be treated.
|Scarlet fever*||1-3 days||Moderate within families.|
Infective first 3 days of treatment.
|24 hours after starting antibiotic treatment.||Moderate within families.|
|Threadworms||n/a||Until all worms are dead.||None||Good hygiene helps.|
Case and family contacts should be treated.
|Tuberculosis*||n/a||Until 14th day of treatment.||Variable, consult local health protection unit.||See 2nd Reference below.|
|Warts and verrucas||n/a||None||None||Care needed with verrucas in swimming pools, gymnasiums and changing rooms.|
|Whooping cough*||7-10 days||Mainly early catarrhal stage, but until 4 weeks after onset of cough paroxysms.|
Shorten to 7 days if given antibiotics.
|5 days from commencing antibiotic treatment, or 21 days from onset of illness if no antibiotic treatment.||Check immunisation of contacts.|
Highly infectious in non-immune populations.
Dr Tim Kenny
Dr Hayley Willacy
Dr Colin Tidy