In rural Uganda, HHV-8 infection was prevalent in early childhood and increased with age throughout adulthood, with the majority of infections occurring before age 14 years. This age-dependent pattern is consistent with other studies in countries where KS is endemic [4
] including Uganda [5
]. The observed pattern of increasing seroprevalence of HHV-8 infection with increasing age was similar to that seen for HSV-1, HBV, EBV, and CMV infection, all of which are viruses known to be transmitted horizontally during childhood [33
]. This pattern suggests that HHV-8 is mainly spread through nonsexual, horizontal routes during childhood and that transmission is ongoing throughout the adult years.
Common to all of the viruses examined—HHV-8, HSV-1, HBV, EBV, and CMV—is their presence in saliva [13
], a recognized vehicle for transmission for these viruses and a possible explanation for a pattern of horizontal nonsexual spread among African children. To our knowledge, this is the first study to examine whether exposure to saliva through specific acts practiced with young children contributes to transmission of HHV-8 to children in sub-Saharan Africa. In our study, children who frequently shared food or sauce plates with other household members, among whom ≥1 were HHV-8 seropositive, had a marginally higher odds of being HHV-8 seropositive than those children who never shared a common plate. It is plausible that children who come into close contact with food or sauce plates shared with others are exposed to saliva of other household members, especially other children, who are actively shedding HHV-8 virus. It is also possible that this act is correlated with behaviors not examined here. Indeed, there are possibly a number of other acts by which children are exposed to saliva in this community, as have been revealed by more recent work in other sub-Saharan African communities [34
]. We did not detect an association between reported exposure to food premasticated by the mother and seropositivity to any of the viruses examined. This could possibly be because mothers who were seropositive owing to distant childhood infection could have been shedding much lower numbers of viral particles in their saliva when the act occurred, compared with, for instance, younger siblings who were more recently infected. Furthermore, our inability to detect associations between risk factors examined and infection with HHV-8 or other viruses could be attributable to type II error, especially in the younger age groups, chance, or failure to measure risk behavior in caregivers other than the mother.
The finding of a 2–4-fold increase in seroprevalence of HHV-8 infection among children and adults living in households with ≥2 HHV-8–seropositive household members, compared with children and adults living in households with no other HHV-8–seropositive person provides evidence for intra-household HHV-8 transmission in children and adults. However, our observation of an age-related increase in seroprevalence of HHV-8 infection among children regardless of the presence of other HHV-8–seropositive household members suggests that transmission from HHV-8–infected persons outside the household may also be important. These findings, consistent with data from prior other studies [12
], imply that household members and persons residing outside the household may play an important role in the transmission of HHV-8 to children. Furthermore, we found that parental HHV-8 serostatus was independently associated with that of their child, although we found no association between child's infection status and that of her/his mother or father specifically.
Among children, seroprevalence of HHV-8 infection did not differ significantly by sex, but among adults, HHV-8 seroprevalence was significantly higher among men than among women, a finding that is consistent with at least 1 other report from this region [12
]. Consistent with other studies of adults in sub-Saharan Africa [27
], we found no evidence for an association between HHV-8 seropositivity and number of lifetime sex partners, history of genital ulcers, history of vaginal/penile discharge, or HIV infection. Furthermore, although there was an overall increase in HHV-8 seroprevalence with age in adults, there was little increase in HHV-8 seroprevalence in both women and men aged 14–34 years, the years of peak sexual activity with different partners. These findings are in marked contrast to our findings for HIV and HBV infection, both of which increased sharply after age 15 years and were significantly associated with all indicators of sexual activity. Although a statistically significant association between HHV-8 and HBcAb was observed for women, the association could also be explained by nonsexual horizontal transmission of HHV-8. Although we cannot rule out the possibility of some HHV-8 spread through sexual activity, the lack of association between HHV-8 serostatus and indicators of sexual activity suggests that it does not play a substantial role in transmission in our population.
A limitation of our work is the self-reported nature of acts in which saliva may be passed to children and, among adults, sexual behavior. However, because public health messages pertaining to either hygiene-related behavior or sexual behavior generally do not mention saliva, we do not believe that participants have underreported practices to provide socially desirable responses. Neither interviewers nor participants knew the participant's HHV-8, CMV, HSV-1, EBV, or HBV serostatus, thereby minimizing selective reporting. Finally, the cross-sectional study design precludes our ability to determine when infection occurred, and thus, it is not possible to establish causal associations between the behaviors examined and infection with HHV-8 or the other viruses examined.
In conclusion, we found seroprevalence of HHV-8 infection to be high among young children and to increase with age among children and adults in rural East Africa. HHV-8 transmission in this population appears to be mainly attributable to horizontal transmission from members in and outside households. Furthermore, our data suggest that transmission is ongoing in adulthood, most likely by nonsexual routes. Although the importance of horizontal transmission in childhood is evident, the specific routes of horizontal transmission remain unclear, and they need to be further investigated before effective prevention messages can be given. It is only through prospective longitudinal observation of uninfected newborns in their early childhood years in conjunction with detailed examination of their close contacts (ie, parents, siblings, other household members, and other persons outside of the home who have close contact with children) that we can definitively understand the types of interpersonal contact that transmit HHV-8, the biological factors in the infected and at-risk persons that mediate infectiousness and susceptibility to infection and the behavioral aspects of these contacts that mediate transmission.