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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 |
- HPA Guidelines on the Management of Communicable Diseases in Schools and Nurseries.[As PDF]
- 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.
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