In a study of individuals who provided daily genital swabs for at least 30 days, virus was detected twice as often among those with a symptomatic infection (20.1% versus 10.2% of days, P<0.001), according to Anna Wald, MD, MPH, of the University of Washington in Seattle, and colleagues.
The proportion of days on which virus was shed in the absence of lesions -- subclinical shedding -- was also higher in symptomatic patients (13.1% versus 8.8%, P<0.001), the researchers reported in the April 13 infectious disease and immunology theme issue of the Journal of the American Medical Association.
But for each subclinical shedding episode, the amount of virus shed was similar in the symptomatic and asymptomatic groups -- 4.3 and 4.2 log10 copies, respectively (P=0.27).
That finding "underscores the epidemiologic observations that the risk of HSV-2 transmission is high from persons with unrecognized HSV-2 infection," Wald and her colleagues wrote.
"Our findings suggest that 'best practices' management of HSV-2-infected persons who learn that they are infected from serologic testing should include anticipatory guidance with regard to genital symptoms, as well as counseling about the potential for transmission," they wrote.
According to the researchers, 16% of U.S. adults are HSV-2 seropositive, although only 10% to 25% of them have recognized genital herpes.
There is uncertainty about how to manage patients with asymptomatic infections, Wald and her colleagues wrote, which is at least partly attributable to the lack of knowledge about the natural history of the infection in these patients.
To explore the issue, the researchers examined HSV-2 genital shedding among adults with both symptomatic infection (410 patients) and asymptomatic infection (88 patients). The asymptomatic patients were identified as part of the enrollment process for a study of a prophylactic HSV-2 vaccine.
All participants were instructed to collect swabs of genital secretions and inspect the genital region for lesions every day for at least 30 days.
The symptomatic patients identified lesions during follow-up more frequently than asymptomatic patients -- 63.9% versus 21.6%.
A greater percentage of days with viral shedding were accompanied by lesions in the symptomatic group (43% versus 16.4%, P<0.001).
In a multivariate analysis, an asymptomatic infection was significantly associated with a lower risk of genital shedding (RR 0.57, 95% CI 0.42 to 0.77).
Other predictors of viral shedding included having at least eight recurrences per year (RR 1.57, 95% CI 1.25 to 1.97) and white race (RR 1.74, 95% CI 1.31 to 2.31).
"The issue of infectivity is both a patient management and a public health concern," according to the authors.
Although several strategies, including condom use, daily valacyclovir therapy, and disclosure of HSV-2 serostatus, are each associated with a halving of the risk of transmission, "these approaches reach a small portion of the population and have not had an influence on HSV-2 seroprevalence in the last decade," they wrote.
"We hope that these data will result in further discussions regarding control programs for HSV-2 in the U.S."
The study was supported by grants from the NIH.
Wald reported receiving research support from the NIH and GlaxoSmithKline and consulting for AiCuris. Her co-authors reported relationships with the NIH, GlaxoSmithKline, AiCuris, and Immune Design. One of the authors reported consulting for AiCuris, being listed as a co-inventor on several patents describing antigens and epitopes to which T-cell responses to HSV-2 are directed, and receiving fees for serving as the head of the scientific advisory board of Immune Design, including equity shares that are less than 1% ownership.
- Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner
Journal of the American Medical AssociationSource Reference: Tronstein E, et al "Genital shedding of herpes simplex virus among symptomatic and asymptomatic persons with HSV-2 infection" JAMA 2011; 305: 1441-1449.