Two novel observations emerge from this study. The first is that the cohort of the current generation of African-American children and adolescents in Richmond VA has lower rates of CMV seroprevalence than the older generation comprising their parents and caretakers. We observed a rate of CMV infections for female adults and caregivers that averaged 70%. This rate of seropositivity is similar to those previously reported by us for Richmond and is similar to those reported for adults in other US cities [1
]. Further, in a population-based survey of African-Americans for the entire US, the average rate of seropositivity for African-American adults was 75.8% [4
]. All of the published adult data were obtained in the late 1980s and early 1990s. A study conducted in the late 1980s in Houston reported infection rates for African-Americans between 6 and 22 years of age which increased with age from 30% to 75% [2
]. Similarly, in the US population-based study, infection rates for African-Americans tested between 1988 and 1994 from 6 to 20 years of age ranged from 40% to 65% [4
]. These rates are similar to those we observed for the current generation of adult females.
Ours is the first recent study to determine CMV seroprevalence rates for the current generation of lower socioeconomic African American children and adolescents. We did not measure the seroprevalence rates in age-matched Caucasians. However, the low rates we observed for lower socioeconomic African American children and adolescents were nearly identical to the low seroprevalence rates reported for Caucasians children and adolescents measured for the entire US population between 1988 and 1994 and for Caucasian children measured in Houston Texas in the late 1980s [2
]. In contrast, in these studies the seroprevalence rates for African-American children were significantly higher than age-matched Caucasians. Thus our data suggest the current generation of African-American and Caucasian children will have similar CMV seroprevalence rates.
Our observations may be explained by two factors. First, our subject sample may not be representative of the population of African-Americans residing in Richmond, VA or elsewhere especially since we selected subjects seeking medical consultation. This seems unlikely for two reasons. As discussed above, we observed seroprevalence rates for the adults who were predominantly female which were similar to those previously reported for Richmond and other US cities [1
]. Second, our population was similar in demographic characteristics to that described by the US census for African-Americans in residing the City of Richmond, the state of Virginia, and the nation.
A second more likely reason we observed a lower rate of seroprevalence among African-American children may relate to the infrequent sexual activity reported by our adolescents. The preadolescent seroprevalence rates we observed were similar to those reported in the Houston study (30%–40%) and in the population-based US study (40%) [2
]. However, in both these studies there was a marked increase in infections rates among adolescents. Sexual activity during adolescence has been frequently associated with increased rates of CMV infection [6
]. Hence our results suggest a decrease in CMV infection in the current generation of African-Americans may have occurred due to decreased sexual activity, increased condom use, or a reduced number of sexual partners during adolescence. AIDS awareness may in part be responsible for this and it will be important to determine if similar changes in sexual behavior and CMV infection rates is also occurring among lower socioeconomic African-American children and adolescents in other cities.
Other factors such the number of children per household and/or changes in hygienic practices may also account for the reduced rate of CMV seroprevalence infections we observed in the current generation of African-American adolescents and children as compared to the higher rates observed in their parents and in older studies.
We observed a decline in the seropositivity rate with age for African-American adults between 40 and 45 years of age. The significance, if any, of this observation is uncertain This decline was not due to reduced antibody levels in saliva associated with aging since antibody titers to CMV persist for life and actually increased throughout adulthood with highest levels in the elderly [11
]. Although this decline may represent another cohort of older African-Americans with lower infection rates, the number of subjects in this age range was low and thus the 95% confidence intervals were wide and as shown in figure , the 95% confidence intervals overlapped.
The second novel observation from our study was that sibling-to-sibling transmission may have been the primary mode of CMV acquisition among African-American children and adolescents. This was very different than we previously observed among Caucasian children in day care [12
]. For those Caucasian children, child-to-child transmission of CMV acquired in day care was very common but sibling-to-sibling transmission at home seldom occurred. In the current study only 19 children reported day care attendance. Children not in day care probably spend more time at home with their siblings than occurs for children attending day care. Since child-to child transmission of CMV requires prolonged and frequent contact; the association of seroprevalence rates among African-American siblings, most of whom received home care, may represent sibling-to sibling transmission.
In our study 91% per cent of the caregivers were the biological mothers and over 70% were seropositive. Thus our data further indicate CMV acquisition by children from maternal sources such cervical-vaginal secretions, breast milk, or saliva is unlikely to account for the high rate of CMV infections among African- American adults. If infection from maternal sources occurred frequently, the children we observed should have had high CMV seroprevalence rates.