SIXTH DISEASE Human herpesvirus 6 (HHV-6) causes sixth disease, also known as roseola infantum or exanthem subitum. Ninety percent of children have been infected by 2 years of age, with peak incidence occurring between 9 and 21 months of age.14 HHV-6 is most likely transmitted via the saliva of healthy individuals and enters the body via a mucosal surface. One percent of HHV-6 infection is acquired congenitally without known sequelae, similar to the transmission rate of cytomegalovirus.15
Clinical presentation: Only 20% may exhibit a rash
After an incubation period of 10 to 15 days, sixth disease is characterized by a prodrome of mild rhinorrhea, sore throat, and conjunctival redness, followed by a high fever (100.4°F to 104°F).16 Cervical, postauricular, or occipital lymphadenopathy usually develops. Other symptoms are usually absent but may include abdominal pain, vomiting, or diarrhea. After 3 to 5 days, the fever abates and the rash of roseola may begin—if at all— as tiny, erythematous, raised papules on the trunk that spread to the neck and extremities (FIGURE 2), lasting 1 to 3 days. Interestingly, while 93% of those infected are symptomatic (fevers, fussiness, rhinorrhea), only 20% of those infected exhibit the rash of roseola.1 Nagayama spots (ulcers at the uvulopalatoglassal junction) can be seen in Asian infants.
