Genital herpes, a recurrent life-long infection caused by either herpes simplex virus type 1 (HSV-1) or HSV-2, is one of the most prevalent sexually transmitted infections in industrialized countries.1,2 It can cause considerable morbidity for those infected, increases the risk of HIV acquisition and transmission, and may lead to congenital and neonatal infections.1,3,4 Up to 90% of those with HSV infection are unaware of their status, over 50% shed HSV subclinically in the genital area, and at least 70% of transmissions occur during periods of asymptomatic shedding.1,5 The use of antiviral drugs, specifically valacyclovir, has been demonstrated to reduce sexual transmission of HSV-2 infection by approximately 50% in HIV negative patients.6
Numerous studies have shown an interaction between HSV-2 and HIV-1.7–9 HSV-2 facilitates acquisition and transmission of HIV at least 2-fold4,9 and may accelerate the course of HIV progression.10–14 HIV-positive individuals may have more frequent and more severe recurrences of genital herpes and are 4 times more likely than HIV negative individuals to have subclinical shedding of HSV-2.15,16
Data on the seroprevalence of HSV among HIV-positive individuals demonstrates geographic differences with rates reported to range from 30% to 70% in the United States and Europe and 50% to 90% in Africa.17–23 HSV-2 seroprevalence rates are higher in HIV-positive than in HIV negative persons and have been reported to be especially high among HIV-positive persons in sub-Saharan Africa. HSV suppressive therapy in HIV-infected persons not only decreases the frequency and severity of HSV recurrences and shedding but can also result in a decrease in HIV levels in the blood and genital tract.12,24 Although it has been shown that acyclovir given as HSV suppressive therapy in at-risk HSV-2 seropositive women does not decrease the incidence of infection with HIV,25,26 there are ongoing studies examining the hypothesis that suppression of genital herpes with antiviral agents in HIV-infected patients may decrease transmission of both HSV and HIV. Coinfected individuals often do not have a clinical history of genital herpes, and identifying those infected may facilitate optimal patient management together with risk reduction counseling for both infections to help prevent further transmission.27–29
The aim of this study was to determine the seroprevalence of HSV in a population of HIV-1 positive patients in Canada and examined correlations with risk behavior, clinical history, level of immunosuppression, and antiretroviral therapy.
Sequential patients infected with HIV-1 attending 5 infectious disease clinics in Canada [Edmonton (3 clinics), Quebec City, and Toronto], who were able to provide informed consent, were approached to participate in the study between October 2005 and April 2007. Recruitment was stratified by HIV-risk behavior. The N for each group was based on the anticipated prevalence of infection in that group. Risk behaviors were mutually exclusive and subjects were assigned as follows: men who had sex with other men (MSM), injection drug use since 1985 regardless of sexual orientation, endemic–adults born in, or who had sex with someone born in a country where heterosexual transmission is believed to be the predominant mode of HIV transmission (formerly classified as pattern II countries), and heterosexual. Patients were asked to participate only once.
After informed consent was obtained, patients completed a self-administered questionnaire and had blood drawn for type-specific herpes serology. The questionnaire addressed HIV-risk behavior, duration of HIV infection, history of oral and/or genital herpes, frequency of recurrences, and treatment for HIV and/or genital herpes. The last CD4 count and HIV viral load were abstracted from the medical record. All participants received nominal financial compensation of 15 Canadian dollars.
The questionnaire and blood sample were labeled with a 4 digit numeric code which was matched to the individual at the study site only. The study was approved by the Health Research Ethics Boards at the University of Alberta, Centre Hospitalier Universitaire de Quebec, and the University Health Network, Toronto.
Blood samples were allowed to clot at room temperature, centrifuged, and serum was aseptically transferred to a sterile tube and immediately placed into a −70°C freezer. Samples were shipped on dry ice to a central research laboratory where all testing was performed (L.M.).
Samples were analyzed by enzyme-linked immunosorbent assay (ELISA) for the qualitative detection of human IgG class antibodies to HSV-1 and HSV-2 (Focus Diagnostics HerpeSelect HSV-1, HSV-2 ELISA IgG). Sample optical density readings were compared with reference cutoff optical density readings to determine positive, negative, or equivocal status. Equivocal samples were rerun and if the ELISA remained unchanged, the sample was sent to the University of Washington Virology Laboratory (Seattle, WA) for Western blot HSV type-specific testing.30 The Western blot results were reported as positive, negative, or equivocal.
Data Management and Analysis
Questionnaire responses and corresponding serology results were entered twice into a data base. Statistical analysis was undertaken using SPSS (Statistical Package for Social Sciences, Chicago, IL) 11.5 for Windows. Bivariate analyses, using standard contingency table methods, examined the association between demographic and medical variables and 3 outcomes: HSV-1 seropositivity, HSV-2 seropositivity, and those seropositive for both HSV-1 and HSV-2. The t test was used for continuous variables. Odds ratios and 95% confidence intervals (CIs) were calculated. Significance was set at P ≤0.05.
Edmonton recruited 46% of subjects, Quebec City and Toronto each recruited 27%. There were no statistically significant differences by location, therefore all results are aggregated.
Six hundred twenty-nine subjects with a mean age of 43.9 years (range 19–71 years) agreed to participate (Table 1). Men accounted for 72.3% of all subjects. The majority of men reported MSM as their risk behavior followed by injection drug use. The risk behavior for most women was heterosexual followed by endemic. There were a significantly lower proportion of women who were Canadian born than men (60.9% vs. 80.0% P <0.001).
Almost half (46.9%) of the study participants were 45 years of age or older. Women were younger and for the age group of 25 to 34 years, there were 3 times as many women. There were almost twice as many men over the age of 45 than women (54.3% vs. 27.6%). When age was examined by risk group, there were a higher proportion of subjects 45 years or older in the MSM group, whereas the endemic group had the highest proportion of 35 to 44 year olds. There were a fairly equal proportion of under-25-year olds in all risk behavior groups.
Of Canadian-born subjects, 77.3% were white, 13.0% were First Nation, and 7.4% were Métis. Canadian-born women were 2.8 times more likely to report being either First Nation or Métis than Canadian men. For subjects born outside Canada, 54.1% indicated their race as black, 22.6% white, 8.2% Hispanic, 5.7% Asian, and 5.0% East Indian.
Men were known to be HIV-positive for a longer period of time than women with 67.8% of men diagnosed before 2001 compared with 54.9% of women (P <0.001) (Table 1). When examined by risk behavior the proportion first diagnosed in 2001 or later were 26.1% of MSM, 41.9% of heterosexuals, 40.8% of injection drug users, and 54.9% of the endemic group.
Significantly more men than women had ever received antiretroviral therapy (ART) and the mean length of HIV-1 infection was longer for those on ART (9.7 years compared with 4.3 years P <0.001) (Table 1). MSM were more likely to have ever received ART (88.6%) followed by injection drug users (78.5%), heterosexuals (77.1%), and the endemic group (75.6%) (P = 0.002). There were no significant differences by CD4 count for those currently receiving ART. Not surprisingly the HIV viral load was significantly lower for those on ART, with 98.1% of this group reporting an undetectable viral load (P <0.001).
A significantly greater proportion of men reported a history of oral cold sores (P = 0.007) although more women reported a history of genital herpes (P = 0.026) (Table 1). There was a significant association between risk behavior and oral cold sores with injection drug users and MSM reporting the highest proportion (67.2% and 63.5%, respectively) versus heterosexuals (49.6%) and the endemic group (37.3%) (P <0.001). There were no statistically significant differences between a history of genital herpes and risk behavior. Of the participants who reported a history of genital herpes, a greater proportion of men were currently receiving antivirals agents (43.1% vs. 28.9%). Of subjects taking antiviral medications for genital herpes, 42.4% reported taking pills every day with the remaining 54.5% taking medications only during an outbreak.
There were 7 equivocal results with ELISA which were tested by Western blot. One sample remained equivocal by Western blot.
The overall seroprevalence for HSV-1 and -2 was 78.1% and 54.6%, respectively (Table 2). Women were 2.7 times (95% CI: 1.8–3.9) more likely to be HSV-2 seropositive than men (71.3% vs. 48.2% P <0.001) but there were no significant associations between HSV-1 status and gender. Country of birth and race were both statistically significant with participants born outside Canada being 2.5 times (95% CI: 1.5–4.2) more likely to be HSV-1 positive and 2.0 times (95% CI: 1.4–3.0) more likely to be HSV-2 positive. Participants who described themselves as nonwhite are 3.2 times (95% CI: 2.2–4.5) more likely to be HSV-2 seropositive.
There was also a statistically significant association between risk behavior and both HSV-1 and -2 seropositivity. Participants identified as endemic were 4.1 times more likely to be HSV-1 seropositive (95% CI: 1.7–9.8) and 3.7 times more likely to have HSV-2 (95% CI: 2.2–6.5) (Table 2). Heterosexuals had a statistically higher rate of HSV-2 but not HSV-1. MSM had the lowest seroprevalence of HSV-2 (45.3%). There were no statistically significant associations between HSV status and age group, length of HIV-1 infection, CD4 count, or HIV viral load.
Almost one-third of men and women were seropositive for both HSV-1 and -2 (34.9% men; 26.4% women). HSV-1 and -2 seronegative men and women represented 23.3% and 8% of each group, respectively.
HSV Medical History
For participants who were HSV-1 positive, 63.3% reported a history of oral cold sores. Of HSV-2 positive subjects, only 30.3% reported a history of genital herpes. The only significant factor for a history of genital herpes was being a woman. Country of birth, race, and risk behavior were not significant. The remaining participants with a history of genital herpes were HSV-2 negative but HSV-1 positive. However, there were 202 (58.9%) individuals who were HSV-2 seropositive with no history of genital herpes and therefore presumed to have asymptomatic or unrecognized infection.
The seroprevalence of HSV-2 antibodies was 54.6% in persons coinfected with HIV-1 but varied by gender, country of birth, race, and HIV-risk behavior. This was lower than we expected especially among MSM. The rate of 45.3% in our MSM study population is in comparison with that of 80.5% reported in Peru19 and 61% in Australia.31 Cachay et al.23 found a rate of 41.5% in a group of HIV-infected men in the United States, 90% of who identified themselves as MSM. The high level of HSV-2 in our endemic population is in keeping with data reported by others.11,20 Among injection drug users, our rate of 60.8% is higher than the 44% reported from the United Kingdom.21
Women are recognized to be at higher risk for acquisition of genital herpes because of potential exposure of a large mucosal area, which is susceptible to micro abrasions and lacerations during sexual activity. The women who participated in our study had a 2.7-fold increased risk of being HSV-2 seropositive, consistent with other reports.20,21,32
Country of birth and race were also significant findings in our study. Individuals who were born outside Canada and were nonwhite had a 3.2-fold increased risk of infection. This is reflected in the HSV-2 seroprevalence rate of 75.6% in the endemic group. Age was not a factor for HSV-2 infection but our study population was older with a mean age of 43.9 years. Others have reported increasing seroprevalence with age although the highest rate for HSV-2 has consistently been reported in both men and women >40 years of age.21,32
Despite significant differences in HSV-2 seroprevalence and risk behavior, there were no differences in participants reporting a history of genital herpes by risk behavior. However, significantly more women recognized their infection. The majority of participants (58.9%) who were HSV-2 positive did not give a history of genital herpes and only 42.4% of those with a history of genital herpes were on daily antiviral therapy.
Clinical reactivation of HSV-2 has been shown to exacerbate HIV-1 resulting in an increase in plasma HIV-1 viral load, which can persist for up to 6 weeks.10,11 The proposed mechanism is through an influx of activated CD4 cells and T lymphocytes at the time of HSV-2 reactivation, which unregulates HIV-1 replication.
The large proportion of HSV-2 positive participants without a history of genital herpes in our study reinforces the importance of routinely undertaking HSV-2 screening with type-specific serology. The risk factors identified as significant for HSV-2 in our study were women, born outside Canada, nonwhite, and the risk behavior of endemic and heterosexual. However, selective screening of only those individuals would miss a large number of infections. The goals of screening for HSV-2 are to identify persons at higher risk of transmitting HIV infection because of unrecognized HSV-2 coinfection, to improve the health of HSV-2 and HIV coinfected patients and to identify persons negative for HSV-2 who may be at increased risk of acquiring HSV-2. Those identified on screening as HSV-2 positive could then be educated to recognize symptoms and signs, counselled in risk reduction activities, and be offered treatment options.27–29 Nucleoside analogs (acyclovir, valacyclovir, and famciclovir) decrease the frequency and severity of HSV-2 recurrences and asymptomatic HSV-2 shedding and are effective, safe, and well-tolerated drugs in patients with HIV-1 infection. The use of daily valacyclovir can also significantly reduce the risk of sexual transmission of HSV-2 infection.6 These agents do not interact with any of the antiretroviral drugs. Nucleoside analogues may also decrease HIV-1 levels in the blood and genital tract, offering further clinical and public health benefits. Recent reports utilizing valacyclovir suppressive therapy in coinfected women demonstrated a significant decrease in the frequency of genital HIV-1 RNA and the mean plasma HIV by 0.53 log10 copy per milliliter.24 Another report in coinfected men, again utilizing suppressive valacyclovir, found a significant reduction in rectal and plasma HIV-1 levels.12 Although we do not yet have evidence that the treatment of “asymptomatic” HSV-2 in coinfected individuals would change the natural history of HIV, identification, education, and treatment of HSV-2 would have a positive public health benefit from a genital herpes point of view.
In conclusion, the seroprevalence of HSV-2 infection in our HIV-1 study population was 54.6% with significant differences identified by risk behavior, gender, country of birth, and race. However, only a small proportion of those infected recognized their infection. Our findings stress the need for introducing type-specific HSV-2 testing for HIV-positive individuals. Identification of HSV-2 positive individuals would allow for directed education regarding symptoms, signs, and transmission reduction including consideration of antiviral therapy for improved management of both infections.
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