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Incubation Times and Infectivity

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; the following is a guide. For a slightly more comprehensive list - see HPA site1
Note: *= a notifiable disease (UK).
CDC=communicable disease consultant.


Disease Incubation Infectivity Exclude until Comments
Adenovirus Gastroenteritis 8-10 days 6-16 days 24 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
Immunocompromised contacts need prophylaxis
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
Conjunctivitis 3-29 days
Mean=8		 While active (direct contact). Infective up to 2 weeks None Transmission more likely in young children by direct contact - very little data.
Fifth disease (slapped cheek) 13-18d 30% in families
10-60% in schools		 None - only likely to be infective in prodrome. Avoid infection in pregnant women and the immunosuppressed.
Glandular Fever 33-49d At least 2 months Person is well  
Hand, foot & mouth disease 3-5d Up to 50% in homes and nurseries None HYGIENE helps. Stool excretion for continues for SOME weeks. Avoid infection in pregnant women.
Head Lice   While harbouring lice No exclusions (No evidence that exclusion of affected children has any effect on the spread) Education is important. Note need for treatment of cases and contacts shown to have head lice
Hepatitis A 15-50d From 2 wks before to 1-2 wk after jaundice onset Children < 5 yrs: 5 days. Children > 5 yrs: none HYGIENE needs emphasizing
HSV cold sores 1-6d While lesions are moist None Highly infectious, especially among young children.
AVOID kissing
Impetigo Skin carriage 2-33 days before development of impetigo (Strep) High (strep) low (staph) Until lesions healed or crusted (little firm evidence)  
Measles* 6-19d Highly contagious in non-immune population
A few days before to 6-18d after onset of rash		 5d from onset of rash Check immunization
Risk of serious infection in immunocompromised host (give prophylaxis)
Mumps* 15-24d 10-29 days. Moderate infective in unimmunised population. 5 days from onset of swelling. Often not effective as transmission occurs before symptoms. Outbreaks reported in vaccinated secondary schoolchildren
Ringworm Varies Until lesions resolve None. Low infectiousness HYGIENE helps
Rubella* 13-20d 1 week before to ~4d after onset of rash 5 days from onset of rash. Check ALL female contacts are immune
Scabies Varies Until mites & eggs dead 24h of treatment Risk of transmission is low in schools but outbreaks do occur. Close contacts should also be treated
Scarlet fever* 1-3d Moderate within families. Low elsewhere. Infective first 3d of treatment Suggest 5 days if treated (little evidence - epidemics used to occur)  oderate within families. Low elsewhere
Threadworms   Until all worms dead No exclusions HYGIENE helps. Case and family contacts should be treated.1
Tuberculosis*   Until 14d of treatment Variable see Guidelines 2
Verrucae   None Continue all activities; ?cover with a dressing. Care needed with verrucas in swimming pools, gymnasiums and changing rooms.
Whooping cough* 7-10d Mainly early catarrhal stage, but until 4 wks after onset of cough paroxysms; shorten to 7d if given antibiotics 5 days if given erythromycin or azithromycins, otherwise >3w Highly infectious in non-immune populations
CHECK on immunization of contacts

References Used

  1. HPA Guidelines on the Management of Communicable Diseases in Schools and Nurseries.[As PDF]
  2. Joint Tuberculosis Committee of the British Thoracic Society. Control and prevention of tuberculosis in the United Kingdom: code of practice 1994. Thorax 1994; 49: 1193-1200.

Acknowledgements EMIS is grateful to Dr Huw Thomas for updating this article. The final copy has passed peer review of the independent Mentor GP authoring team. ŠEMIS 2005.

Last issued 30 Aug 2006









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PS - Health and Poverty

Perhaps the biggest cause of ill health in the world is poverty. Help to Make Poverty History. For example, why not lend some of your money to disadvantaged communities to enable them to trade their way out of poverty through schemes such as Shared Interest.

See also MAKEPOVERTYHISTORY North East for details and links to campaigns against poverty.

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