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Paper text:
methods for the study to assess hepatitis c risk have been summarized ( 7 ) . in brief , during march 2009june 2010 , persons 1840 years of age who were residents of san diego county , california , and who had injected drugs in the previous 6 months were recruited to participate in this study .
eligibility screening and acquisition of informed consent for potential participants were followed by a behavioral risk assessment and serologic testing .
data collected included participant demographics , substance use , injection practices , diagnosis with sexually transmitted infections , exchange of sex for money , homelessness , travel to mexico , and hiv status .
serologic testing included detection of antibodies against hepatitis a virus ( hav ) , hepatitis b virus core antigen , and hepatitis c virus ( hcv ) by using the vitros immunodiagnostic system ( ortho clinical diagnostics , rochester , ny , usa ) , and igg against hev by using a commercial assay ( dsi , saronno , italy ) .
we performed a comparative analysis of all persons on the basis of their status for igg against hev by using demographics , seropositivity for other viral hepatitides , travel to mexico , history of incarceration , homelessness , hiv status , and high - risk sexual behavior .
we used bivariate logistic regression to calculate odds ratios ; 95% cis ; and p values , which were set at 0.05 to determine significance for factors associated with hev prevalence .
all data were analyzed by using sas version 9.2 ( sas institute , cary , nc , usa ) .
of 508 pwid , 72% were men , their mean age was 29 years ( range 1840 years ) ; and 62% were white .
fourteen ( 2.7% ) persons had igg against hev ; none of these persons were positive for hev rna by pcr ( all were negative for igm against hev ) .
of the 14 persons with igg against hev , 11 ( 79% ) were men ; their mean age was 33.4 years ( range 3036 years ) ; and 57% were white ( table ) .
relative to participants < 30 years of age , persons 30 years of age were more likely to be positive for igg against hev ( odds ratio 3.61 , 95% ci 1.319.94 ) .
travel history and presence of antibodies against hav , hepatitis b virus , or hcv were not associated with presence of antibody against hev .
bivariate logistic regression showed that there was no association between presence of igg against hev and a history of incarceration , sharing of injection drug equipment , homelessness , high - risk sexual behavior , and hiv status .
nd , not determined ; hav , hepatitis a virus ; hbc , hepatitis b core antigen ; hcv , hepatitis c virus . 
we found an overall hev seroprevalence of 2.7% in young pwid in the united states .
this seroprevalence was higher among participants 30 years of age than in participants < 30 years of age .
variables typically associated with hcv / hiv transmission ( i.e. , high - risk sexual behavior , incarceration , or sharing of injection drug use equipment ) were not associated with presence of antibodies against hev .
these findings were consistent with results of a study that found no association between antibodies against hev and co - infection with other hepatitis viruses or sharing of drug paraphernalia ( 2 ) .
because of the common mode of fecal  oral transmission of hav and hev , other studies have also investigated an association between hav and hev infections , but results have been inconclusive ( 1,5,6 ) . as in previous studies , we found an association of presence of antibodies against hev and age ( 1,6 ) .
higher prevalence among older pwid suggests that there may be age - related exposures independent of injection drug use that increases the likelihood of hev infection .
this birth cohort effect has been seen in other low - prevalence countries , such as denmark ( 8) , and decreased possible exposure may help explain the lower prevalence rates in our study .
our small sample size reduced the potential to detect significant differences between hev - negative and hev - positive persons .
in addition , we did not have information about other exposures that have been associated with hev infection , including particular dietary or zoonotic exposures or history of travel to a country to which hev is endemic .
information about hev genotype was not available for seropositive persons , which might have provided clues as to the mechanism of exposure .
lower prevalence estimates may also reflect the fact that our population only included persons 1840 years of age .
previous data have suggested that increasing age is associated with higher hev positivity ( 6 ) , particularly in countries in which prevalence is low and infection is caused mainly by hev genotype 3 ( 9 ) .
although our data can not be generalized to the us population , seroprevalence in this study appears to be low , which is similar to time trends in the general population of other low - prevalence areas ( 8) .
variability in assay types used may account for discrepancies seen with previous seroprevalence studies of hev . in a study evaluating the performance and concordance between various assays for detection of igg against hev available at the time ,
overall concordance ranged from 49% to 94% ( median 69% ) , and concordance among reactive serum samples ranged from 0% to 89% ( median 32% ) ( 10 ) .
evaluation of the performance characteristics and concordance of currently available assays for detection of antibodies against hev , including the assay used in this study , remains to be determined .
overall , our data showed an increase in antibodies against hev for pwid 30 years of age and no other association with other reported risk factors .
future research is needed to explore other marginalized populations in hev - endemic areas to determine whether there are other risk factors that have not been identified in low - prevalence areas .
data about prevalence of hepatitis e virus infection in persons who inject drugs are limited . among 1840-year - old persons who inject drugs in california , usa , 
 prevalence of antibodies against hepatitis e virus was 2.7% . 
 this prevalence was associated with age but not with homelessness , incarceration , or high - risk sexual behavior .