Abstract
To examine the seroprevalence of herpes simplex virus type 2 (HSV-2) among Hispanics in the USA, we used the cross-sectional, nationally representative National Health and Nutrition Examination Survey to compare the seroprevalence of HSV-2 between Hispanic persons of Mexican heritage and non-Mexican heritage aged 14–44 years, from survey years 2007–2008. The overall HSV-2 seroprevalence among Hispanics aged 14–44 years was 17.5% (95% confidence interval [CI], 15.2, 20.1) in the USA. HSV-2 seroprevalence was significantly lower among Mexican Americans than among other Hispanics (11.7% vs. 27.8%, P < 0.01). Prevalence of HSV-2 was also significantly associated with gender and age. The significant difference in HSV-2 seroprevalence between Hispanic persons of Mexican heritage and non-Mexican heritage suggested that targeting specific subgroups of Hispanics for preventive interventions may be a strategy to reduce the transmission of HSV-2 and HIV among Hispanics in the USA.
INTRODUCTION
Herpes simplex virus type 2 (HSV-2) is an incurable sexually transmitted infection (STI) that can cause the development of recurrent blisters and ulcers in the genital area. HSV-2 infection has been strongly associated with the increased transmission and acquisition of HIV. 1–5 HSV-2 infection has also been associated with increased risk for other STIs among women caused by the imbalance of vaginal flora from infection. 6,7 More serious but typically infrequent complications of genital herpes include infection of the central nervous system (CNS), neurological problems and neonatal transmission, which can lead to infant mortality or severe CNS complications. 8,9 Data from 1999–2004 show that 17% of the USA population between ages 14–49 is HSV-2 seropositive. 10
Both symptomatic and asymptomatic persons who are HSV-2 seropositive can transmit the virus through sexual contact. 11 Condom use and antiviral medication have been considered as two effective strategies to reduce the risk of HSV-2 transmission, although they are not 100% effective. 12,13 For example, several studies have shown that early diagnosis and treatment with antiviral medications can reduce HSV-2 viral shedding. 14–17 Therefore, it is important for sexually active persons, especially for infected sexually active individuals, to be aware of their HSV-2 status in order to take special precautions or actions to prevent the transmission of HSV-2 or acquiring HIV.
Hispanics are the fastest growing population in the USA and nearly one-third of the Hispanic population is not native to Mexico. 18 The current national HSV-2 prevalence has only been characterized for Mexican Americans. One national study found that Mexican Americans had lower HSV-2 seroprevalence than non-Hispanic whites in the USA 10 However, a recent study found that Hispanics in New York City were more than three times as likely to be HSV-2 seropositive as were non-Hispanic whites. 19 More than 70% of the Hispanic population in New York City is from an Hispanic heritage other than Mexican, with the majority being of Puerto Rican or Dominican descent. 20 To our knowledge, no studies have been conducted comparing the prevalence of HSV-2 between Mexican Americans and persons of other Hispanic heritages at the USA national level.
Our objectives were to estimate the seroprevalence of HSV-2 between persons of Mexican heritage and those of non-Mexican or other Hispanic heritages between the ages of 14–44 years, and to determine factors that are associated with increased HSV-2 seroprevalence, such as demographics, acculturation, health care access and sexual behaviours.
METHODS
Survey design and study population
The National Health and Nutrition Examination Survey (NHANES) is a nationally representative cross-sectional survey that uniquely combines interviews and physical examinations. The NHANES interview includes demographic, socioeconomic, dietary and health-related questions. The examination component consists of medical, dental and physiological measurements, as well as laboratory tests. The NHANES survey began in the 1960s and in 1999 became a continuous programme that samples about 5000 persons every two years. In order to generate reliable statistics certain populations are also oversampled such as Mexican Americans, African Americans and persons over 60 years of age. The methods describing this survey are published elsewhere. 21–23
Our study included 1160 persons aged 14–44 years, who self-reported their ethnicity as Hispanic from the 2007–2008 NHANES data, the first time that the data are able to generate representative estimates for total Hispanics and for Mexican Americans. Hispanics included the persons being of Mexican heritage or of a heritage other than Mexican that could include Puerto Rican, Cuban, Dominican, Central or South American, Other Latin American and Other Hispanic. Informed consent was obtained from all participants or from their legal guardians. This study protocol was approved by the institutional review board of Centers for Disease Control and Prevention.
Survey methods
Notebook computers and electronic pens were used by interviewers to enter participants' responses to general questions. Then, participants used the audio computer-assisted personal self-interview system to listen and to respond to sensitive questions, including questions about sexual behaviours, privately. All persons were asked ‘Do you consider yourself Hispanic or Latino’; if their response was ‘yes’, then they were asked to identify the group or groups that represented their Hispanic origin or ancestry. For the purposes of our study, those who chose Mexican or Mexican American were placed in one group and all other categories were combined to the ‘other Hispanic’ group.
Laboratory methods
Blood samples from survey participants were collected during the health examination. Purified glycoproteins specific to HSV-1 (gG-1) or HSV-2 (gG-2) were used as antigens to detect type-specific antibodies using solid-phase enzymatic immunodot assays. 24,25 The performance of the immunodot assays is high with respect to sensitivity and ability to discriminate between HSV-1 and HSV-2. 24–26
Monoclonal antibodies and affinity chromatography were used to purify gG-2 glycoproteins specific to HSV-2 and used as antigens for solid-phase enzymatic immunodot assays to detect HSV-2 antibodies. Samples positive by immunodot assays were further confirmed by a gG-2 monoclonal antibody inhibition assay.
Statistical analysis
We used SAS software version 9.2 (SAS Institute, Cary, NC, USA) and SAS-callable SUDAAN (Research Triangle Institute, Cary, NC, USA) for all statistical analysis in order to incorporate the sample weights and account for the complex survey design. We used bivariate analyses to examine as to which variables were significantly related to the HSV-2 seroprevalence. Variables that were associated with HSV-2 seroprevalence (P < 0.1) in the bivariate analyses were included in logit models to identify factors independently associated with HSV-2 seroprevalence. In all analyses, a statistically significant difference was defined as a two-tailed probability of <0.05.
RESULTS
Of 1160 Hispanic persons aged 14–44 years, who had HSV-2 antibody test results, the seroprevalence was 17.5% (Table 1). The HSV-2 seroprevalence significantly increased with age from 6.4% in persons aged 14–25 years to 27.6% in persons aged 36–44 years. The seroprevalence was significantly lower among Mexican Americans than among persons of other Hispanic heritages (11.7% vs. 27.8%) and among males than females (13.0% versus 22.5%). The bivariate analyses also showed that the HSV-2 seroprevalence was significantly associated with the region, the language spoken at home, the country of birth and sexual experience. Of females aged 20–39 years, who were classified as other Hispanics, the seroprevalence was as high as 34.9%.
Weighted herpes simplex virus 2 (HSV-2) seroprevalence of Hispanic persons aged 14–44 years from 2007–2008 NHANES
CI = confidence interval; NHANES = National Health and Nutrition Examination Survey
Our multivariate analysis showed that Hispanic persons of non-Mexican heritage had significantly greater odds of HSV-2 (odds ratio [OR] 2.5, 95% confidence interval [CI] 1.4, 4.4) relative to persons of Mexican heritage after adjusting for other factors (Table 2). Women were also significantly more likely to be HSV-2 positive (OR 1.7, 95% CI 1.1, 2.6) than men. The odds of HSV-2 infection also significantly increased with age.
Multivariate associations between selected characteristics and herpes simplex virus 2 seroprevalence among Hispanic persons aged 14–44 years from 2007–2008 NHANES
CI = confidence interval; NHANES = National Health and Nutrition Examination Survey
*P < 0.05 in logistic regression
DISCUSSION
In this nationally representative study, the overall prevalence of HSV-2 among Hispanics was 17.5% with persons of non-Mexican heritage having significantly higher rates than those of Mexican heritage (27.8% versus 11.7%). Compared with non-Hispanic whites or blacks, Hispanic persons of non-Mexican heritage had lower HSV-2 seroprevalence than did non-Hispanic blacks (39.2%), but higher HSV-2 seroprevalence than non-Hispanic whites (12.3%). 10 These data suggest that race and ethnicity need to be considered as we design prevention programmes and interventions for high-risk populations, because HSV-2 infection has been strongly associated with increased transmission and acquisition of HIV. For example, several studies have shown that in communities that are racially and ethnically heterogeneous, persons tend to live and interact predominantly with persons of their own racial background, resulting in the increased spread of infection within groups and limited transmission across race ethnicity boundaries. 27,28 Hispanics are the fastest growing population in the USA; 18 hence it becomes increasingly important to understand the underlying causes of health disparities among different subgroups of the population. The results of this study demonstrate the importance of further exploration of the differences in the prevalence of HSV-2, HIV and other STIs among Hispanic subgroups.
The associations between HSV-2 seroprevalence and being female and increasing age found in this study are similar to those found in other studies. 10,19,29,30 The high HSV-2 seroprevalence (34.9%) among Hispanic women of non-Mexican heritage aged 20–39 years found in this study suggests that many Hispanic women need attention for their initial HSV-2 infection because persons infected with HSV-2 are at greater risk for HIV acquisition, even in the absence of HSV-2 symptoms. The increased susceptibility to HIV infection likely occurs because even HSV-2 ulcerations that are microscopic can provide a portal of entry for HIV, and HSV-2 reactivation recruits potential target cells for HIV to the genital skin and mucosa. Therefore, public health programmes should consider targeting high-risk subgroups of Hispanics, or persons of non-Mexican heritage and develop prevention interventions that are culturally appropriate to these Hispanic subgroups. In addition, because the prevalence of HSV-2 infection is higher among Hispanic persons aged 26 years or older, sexually active persons aged 26 years or older should be aware of their HSV-2 status in order to take special precautions or actions to prevent the transmission of HSV-2 or acquiring HIV.
Our study had several limitations. Owing to the small sample size, we were unable to characterize the seroprevalence of HSV-2 into more specific subgroups of the Hispanic population such as Puerto Ricans, Cubans or Dominicans. Future studies to further characterize those subgroups are needed because they may not be homogeneous in terms of HSV-2 seroprevalence, sexual behaviour or access to health care. A small proportion of persons who reported not being sexually active had also tested positive for HSV-2, suggesting that self-reported sexual activity may not be representative of actual sexual activity.
This nationally representative study highlights the differences in HSV-2 prevalence among different subgroups of the Hispanic population. As suggested by results of our study, persons of Hispanic heritage other than Mexican have a significantly higher prevalence of HSV-2, which may also put them at greater risk of short- and long-term complications of HSV-2 and the acquisition or transmission of HIV. Increased screening and education among Hispanic persons of non-Mexican heritage about the risks of HSV-2 infection may be beneficial to the population in order to properly diagnose and prevent new HSV-2 infections and the transmission or acquisition of HIV.