Exanthema subitum is most commonly affecting children aged 6 months to 2 years. The disease is rare in infants less than 3 months and in children over 3 years of age.
The incubation period is 5-15 days. The infection probably spreads mainly through contact with saliva. Considerable quantities of virus are excreted in the saliva even months after the clinical disease.
Typical exanthema subitum starts with high fever that lasts for 3-5 days, then rapidly decreases and at the same timea fine rash appears (pictures 12). In a small proportion of the children the rash starts during the fever, and in an equal proportion there is an interval of one day between the decreasing of the fever and appearing of the rash. The rash lasts from a few hours to a couple of days.
Separate, small, red macules or maculopapular lesions start around the ears and spread on the face, neck and trunk.
Additional possible findings include conjunctivitis, eyelid oedema, small spotlike papules in the uvula and palate, lymphadenopathy in the neck and occipital area and bulging fontanelle.
Only a minority of children with HHV infection develop the typical exanthema subitum. In most cases the infection manifests a high fever without obvious localizing symptoms.
Febrile convulsions, which occur in 10-15% of infants with the infection, are the most important complication.
In children, HHV may sometimes also cause a true encephalitis. The virus may remain latent in the body and be reactived in association with an organ transplantation or other immunodeficiency state.
Human herpesvirus may play a role in the manifestation of drug reactions.
In the initial phase, the blood picture of most patients with exanthema subitum shows leucopenia.
The determination of CRP concentration is useful if the disease has lasted for more than 12 hours. In exanthema subitum CRP hardly rises at all, whereas in a septic infection it is clearly elevated.
In order to rule out pyelonephritis, a urine sample is taken, as required.
References
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Ahluwalia J, Abuabara K, Perman MJ et al. Human herpesvirus 6 involvement in paediatric drug hypersensitivity syndrome. Br J Dermatol 2015;172(4):1090-5. [PubMed]
Miyazaki Y, Namba H, Torigoe S ym. Monitoring of human herpesviruses-6 and -7 DNA in saliva samples during the acute and convalescent phases of exanthem subitum. J Med Virol 2017;89(4):696-702. [PubMed]