HHV-6B saliva viral loads peak 3-7 months after primary infection

A new study seeking to elucidate the kinetics of HHV-6B shedding in saliva during and after exanthema subitum (ES) found that peak detection rates and viral loads occurred during the convalescent period of ES, between 3 to 7 months post-illness. Detection rates were lower in adults than in children between 3 and 9 years of age, suggesting that HHV-6B may be transmitted to infants to a great extent through the saliva of siblings or other young children and not their parents.


Viral load of HHV-6 & HHV-7 DNA in saliva after Exantem Subitum. Source: Journal of Medical Virology, October 2016.

Previously, infants’ contact with saliva from their mothers has been suspected as the primary mode of transmission. Other family members, such as siblings, have also been suspected, though in light of the results from this study, perhaps not to the extent that is warranted. HHV-6 DNA has been isolated from the saliva of 3-90% of healthy adults (Cone 1993, Di Luca 1995, Pereira 2004), and recent literature has proposed that higher viral loads and rates of shedding in the saliva may be useful biomarkers for fatigue in adults, as they increase during times of stress (Kondo 2005, Osaki 2016). In the present study, HHV-6 was isolated from only 4.3% of adults but 52.2% of children aged 3 to 9. These participants were older siblings and parents of ES patients or children with a history of ES.

The maximal viral loads were observed between 44 and 367 days after the onset of illness. During the acute phase of ES (within 30 days), 81.3% of children showed low HHV-6B DNA detection rates and viral loads.

The high rates of HHV-6 detection in the saliva of young children, as well as their high viral loads, corroborate previous research with similar findings (Gantt 2016) and point to children outside of the immediate family, but in close contact with the uninfected infant, as potentially underestimated sources of infection. This may be especially true of young children who have had ES and who were symptomatic several months prior. A higher index of suspicion for HHV-6B transmission may be warranted among these children.

Read the full paper here: Miyazaki 2016.