Urinary Cytomegalovirus Shedding in the United States: The National Health and Nutrition Examination Surveys, 1999-2004.

Background: There are no data on the prevalence of cytomegalovirus (CMV) shedding from a representative sample of the US population. This information is critical for understanding and preventing CMV.
Methods: We tested urine specimens from CMV immunoglobulin (Ig) G-positive participants aged 6-49 years in 3 racial/ethnic groups from the National Health and Nutrition Examination Surveys 1999-2004 for the presence of CMV DNA using real-time polymerase chain reaction assay. We examined the association of sociodemographic characteristics with shedding prevalence and viral loads.
Results: Among 6828 CMV IgG-positive participants tested, 537 had CMV DNA detected in urine-a shedding prevalence of 9.70%. Among persons aged 6-49 years, shedding prevalence was 3.83%. The prevalence of urinary shedding was inversely associated with increasing age (26.60%, 6.50%, and 3.45% in CMV IgG-positive participants aged 6-11, 12-19, and 20-49 years, respectively; P < .001 for trend test and pairwise comparisons). Urinary viral load also decreased significantly with age (mean, 2.97, 2.69, and 2.43 log10 copies/mL in those age groups, respectively; P < .001 for trend test and pairwise comparisons). Conclusions: Urinary CMV shedding and viral loads decreased dramatically with age, likely reflecting higher rates of primary CMV infection and longer duration of shedding in younger individuals. The findings demonstrate that children aged 6-11 years continue to shed CMV at higher rates and viral loads than adolescents and adults and thus may still be an important source for CMV transmission.