Infectious Diseases

HHV-6 and HHV-7 actually causes infection at a little older age and
more towards the second year of life rather than the first year of life
as we see with HHV-6.
HHV-8 doesn't affect many children. In the past couple of years it has
been described and identified. it is nearly
universally present in all cases of Kaposi's sarcoma tissues. It is also found in AIDS related B- cell
lymphomas that are based in body cavities, and many of those had coinfection with Epstein-Barr virus it isthought that it may actually be necessary to have the HHV-8 for transformation of a
precursor cell that proliferates monoclonally and causes these tumors.
Focusing on HHV-6, a little about the epidemiology and transmission. Roseola was first described in 1913. In 1950, transmissibility
was actually demonstrated although it wasn't until 1986 that the
particular virus was identified. We know that we see these infections year-round and there is worldwide distribution. There is antibody present in 85% of pregnant women with active transport across the placenta. Hence, in the very early weeks, the infants are protected. The antibody declines in the first five months of life to a low of 6%,
then increases to its highest seroprevalence of 86% at one year. So,
by one year of age, most infants have an HHV-6 infection. Titers fall after 40 years of age and there is increased prevalence of IgM six months to one year of age. Saliva is the most likely route of transmission. There is no congenital/perinatal symptom that has been described, and this virus has not been found in breast milk.
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