Doctors are often asked about incubation times for the common childhood infections, so that they can advise about attendance at school etc. Incubation times and infectivity (time when infectious) are variable so the following is only a guide. For a slightly more comprehensive list - see the HPA site referenced below the table.
Note: * = a notifiable disease (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 start of skin eruption.||Traditionally excluded until all lesions are crusted but no transmission recorded after day 5.
Contacts with a weak immune system need prevention.
|Campylobacter||1-10 days||Patients probably not infectious if treated and diarrhoea has resolved.||24 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 - good hygiene helps.||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.||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; otherwise 21 days from onset of illness.||Check immunisation of contacts.
Highly infectious in non-immune populations.
Further reading & references
- Guidance on infection control in schools and other childcare settings, Health Protection Agency, April 2010
- BTS Guidelines; Control and prevention of tuberculosis in the United Kingdom: Code of Practice 2000. Joint Tuberculosis Committee of the British Thoracic Society. Thorax 2000;55:887-901.
Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.
Dr Tim Kenny