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we conducted a cross - sectional study to investigate the seroprevalence and factors associated with kshv infection in amerindian and non - amerindian populations living in 2 regions of the brazilian amazon : a remote rural region of para state ( mapuera , on the banks of the trombetas river ) and manaus , the capital city of amazonas state ( figure ) .
serologic markers of fecal  oral ( hepatitis a virus [ hav ] ) , blood - borne ( hepatitis b and c viruses [ hbv , hcv ] ) and sexually transmitted infections ( treponema pallidum [ syphilis ] and herpes simplex virus type 2 [ hsv-2 ] ) were used as proxies to identify possible routes of kshv transmission in these populations .
map of brazil showing study area ( black box ) in amazonas ( manaus ) and para ( mapeura region ) states . printed with permission of the instituto brasileiro de geografia e estatstica .
a convenience sample of unselected amerindians and non - amerindians living in the mapuera area and a consecutive sample of nonpaid first - time blood donors from the manaus blood bank ( hemoam ) consented to collection of blood samples , as previously reported ( 4,11 ) ethical approval was obtained from the institutional review board of hemoam , the ethical board of the brazilian ministry of health , and the ethics committee of the london school of hygiene and tropical medicine . in the absence of a definitive test to determine kshv infection , all serum specimens were tested by using a previously validated in - house whole - virus kshv elisa ( 12 ) and 2 immunofluorescence assays ( ifas ) that detected antibodies against lytic ( ifa - lytic ) and latent - associated nuclear antigens ( ifa - lana ) ( 12 ) .
serum specimens were also tested for the agent of syphilis by using a t. pallidum  specific assay ( enzygnost syphilis ; dade behring , marburg , germany ) ; for hsv-2 antibodies by using the type - specific herpeselect gg2 elisa ( focus technologies , cypress hill , ca , usa ) , with a higher cut - off ( > 3.5 ) to increase specificity ( 13 ) ; and for hav antibodies by using bioelisa hav ( biokit , barcelona , spain ) .
presence of hbv anti - core antibodies was determined by using ortho hbc elisa ( ortho diagnostics , raritan , nj , usa ) in mapuera serum specimens and hepanostika anti - hbc uni - form ( organon - teknika , boxtel , the netherlands ) in manaus serum specimens .
hcv antibodies were detected by using ortho hcv 3.0 elisa ( ortho diagnostics ) in mapuera serum specimens and murex anti - hcv version 4.0 elisa ( murex biotech s.a .
kshv seroprevalence was calculated separately for men and women and directly age - standardized to the mapuera amerindian population .
the risk associated with kshv infection was estimated with prevalence ratios ( prs ) and 95% confidence intervals ( cis ) , adjusted for sex and age group ( 1824 years , 2534 years , and > 35 years for the blood donor population ; 09 years , 1017 years , 1824 years , 2534 years , and > 35 years for both mapuera populations ) .
the associations of kshv with sociodemographic variables , indicators of socioeconomic status , and other serologic markers were estimated with odds ratios ( ors ) and 95% cis .
variables associated with a significant increased risk for kshv ( p<0.05 ) in univariable analysis were included in a multivariable logistic regression model adjusted for age and sex .
we recruited 339 amerindians ( median age 22 years , interquartile range [ iqr ] 1337 years ; 57.5% female ) and 181 non - amerindians ( median age 17 years , iqr 935 years ; 58.6% female ) in the mapuera communities and 1,133 blood donors ( median age 25 years , iqr 2132 years ; 22.9% female ) in manaus .
the blood donor population had a similar age distribution to that of the adult population in manaus in the 2000 regional census ( 14 ) .
among mapuera amerindians , kshv seroprevalence was 65.0% in those 09 years , increasing to 92.9% in those > 35 years .
in contrast , among mapuera non - amerindians , kshv seroprevalence was 9.8% in those 09 years of age , increasing to 50.0% in those > 35 years of age . among blood donors ,
kshv seroprevalence was 31.3% in those > 35 years of age and 53.8% in the 13 who were of amerindian descent .
after age standardization , kshv seroprevalence remained lower among mapuera non - amerindians ( 30% and 27% among men and women , respectively ) and blood donors ( 16% and 23% , respectively ) than among mapuera amerindians . when results were compared with those of the mapuera amerindians , the age - and sex - adjusted prs were 0.35 ( 95% ci 0.280.45 ) and 0.59 ( 95% ci   0.560.63 ) in mapuera non - amerindians and blood donors , respectively . in each population ,
kshv seroprevalence was slightly higher among females , and increased with age ( p for trend < 0.001 ) in mapuera amerindians and non - amerindians , but not among ( adult ) blood donors ( table 1 ) .
kshv seroprevalence varied little with house crowding ( socioeconomic indicator ) , and hepatitis infections , but was associated with hsv-2 infection in non - amerindians ( or 4.2 , 95% ci 2.18.5 ) and blood donors ( or 1.3 , 95% ci 1.01.7 ) . in amerindians ,
kshv infection was not associated with hsv-2 in univariable analysis ( or 0.7 , 95% ci 0.31.9 ) .
kshv , kaposi sarcoma  associated herpesvirus ; or , odds ratio ; ci , confidence interval ; hsv-2 , herpes simplex virus type 2 . 
in multivariable analysis ( table 2 ) , kshv infection remained associated with female sex among blood donors ( age- and sex - adjusted or [ aor ] 1.3 , 95% ci 1.01.7 ) , and increased significantly with age in both mapuera populations ( p for trend < 0.001 ) .
kshv infection was associated with hsv-2 infection among mapuera non - amerindians ( aor 2.7 , 95% ci 1.26.5 ) and manaus blood donors ( aor 1.3 , 95% ci 1.01.6 ) , but was inversely associated with hsv-2 infection in mapuera amerindians ( aor 0.3 , 95% ci 0.10.9 ) .
* seroreactivity by any serologic assay ( whole virus elisa , ifa - lana , or ifa - lytic ) in multivariable analysis .
kshv , kaposi sarcoma  associated herpesvirus ; ifa - lana , immunofluorescence assay that detected latent - associated nuclear antigens ; ifa - lytic , ifa that detected lytic - associated nuclear antigens ; aor , age- and sex - adjusted odds ratio ; ci , confidence interval ; hsv-2 , herpes simplex virus type-2 .
our data confirm the high kshv seroprevalence observed among amazonian amerindian populations ( 5,7 ) .
however , the inclusion of convenience samples of remote populations and first - time blood donors , who may not necessarily be representative of the adult general population and notably exclude persons who report a range of potentially high - risk behavior for sexually transmitted and blood - borne infections , may have limited the generalizibility of our findings .
high kshv seroprevalence combined with an apparent lack of ks development among amerindian populations support the theory of genetic predisposition to kshv acquisition , as hypothesized for other amazonian populations , in whom segregation genetic analysis has suggested that an unidentified recessive gene may influence kshv serostatus ( 15 ) .
the high kshv seroprevalence ( 65% ) among mapuera amerindians < 10 years of age contrasts with the low ( 9.8% ) seroprevalence among non - amerindians of the same age group living in the same area , which suggests different transmission modes in these neighboring populations .
although we did not collect data on the age of initial sexual experience in either population , the high prevalence in childhood and inverse association with hsv-2 supports nonsexual transmission of kshv in amerindians .
conversely , the association of kshv infection with hsv-2 among mapuera non - amerindians and blood donors supports a role for sexual transmission in these groups , although saliva transmission in younger urban inhabitants can not be ruled out .
universal hav infection status and low rates of hbv and hcv in all populations precluded any meaningful analysis of transmission routes associated with hepatitis viruses . in summary
, this study contributes data on the epidemiology of kshv infection and transmission in some brazilian amazonian populations .
irrespective of urban or rural setting , our data are consistent with a predominant non - sexual transmission of kshv ( most likely through saliva ) in amerindian tribes compared with a probable combination of sexual and nonsexual modes of transmission among non - amerindian populations living in the same region .
to determine the presence of kaposi sarcoma  associated herpesvirus ( kshv ) and other serologic markers , we tested serum specimens of 339 amerindians , 181 rural non - amerindians , and 1,133 urban blood donors ( 13 amerindians ) in the brazilian amazon . 
 high kshv seroprevalence in children and inverse association with herpes simplex virus type 2 indicates predominant nonsexual transmission among amerindians .