76% of Ugandan infants acquire HHV-6B in the first year

Soren Gantt, MD PhD MPH Associate Professor University of British Columbia

Soren Gantt, MD PhD MPH
Associate Professor
University of British Columbia

A new study led by Soren Gantt, MD from the University of British Columbia and Lawrence Corey, MD of the University of Washington revealed risk factors for transmission and symptoms of primary human herpesvirus infections among Ugandan infants.

In this study, 24 of 32 infants were found to have HHV-6 in throat samples or plasma by 12 months. All had HHV-6B, and one had a dual infection of HHV-6A/ HHV-6B. The dominance of HHV-6B over HHV-6A infection was similar to that described in children from North America and Japan but in contrast to earlier studies showing a dominance of HHV-6A in the blood of Zambian infants 80 asymptomatic and as well as in 17 hospitalized febrile infants (Kasolo 1997; Bates 2009 ).

Only three Ugandan infants were found to have HHV-6B in the plasma during primary infection. HHV-6 DNA is rarely found in plasma except during primary infection or acute reactivation.

The investigators concluded that the major risk factor associated with primary HHV-6 infection in Uganda was the quantity of virus shed by household contacts. Of 766 swabs from mothers, 363 (47%) were positive for HHV-6. Out of 810 swabs from other household children, 531 (66%) were positive for HHV-6 DNA. Other viruses found included herpes simplex virus 1 (8%), Epstein-Barr virus (47%), and human cytomegalovirus (59%).

The finding of HHV-6A vs HHV-6B has differed in various studies depending on whether saliva, plasma or PBMCs are utilized, the sensitivity of the assay and the condition of the blood donor or patient. For example, in an a study of healthy donors in Austria, 95% of saliva samples contained HHV-6B, but no HHV-6A could be found in saliva by nested PCR (Aberle 1996). A more recent study in the USA using digital droplet PCR (ddPCR ) found HHV-6 in 57% of 46 blood donor PBMC samples, half of them coinfected both HHV-6A and HHV-6B DNA, but with the HHV-6A viral load quite low (Leibovitch 2014). HHV-6A dominance has been reported rarely in select circumstances such as the plasma of MS patients during relapse (Alvarez-Lafuente 2004), and in fine needle thyroid biopsies of patients with Hashimoto’s Thyroiditis (Caselli 2012).

Of the mothers tested by throat swab, 91% had HHV-6B,  57% had CMV, 100% had EBV,  78% had HSV-1 and 24% had HHV-8. Mothers who were HIV infected were more likely to shed EBV, but shedding of HHV-6B was the same  as in HIV uninfected women. Most of the herpesvirus infections were asymptomatic.

For more information, read the full paper (Gantt 2016).