People with herpes simplex virus type 2 (HSV-2) may still shed the virus even if they do not experience genital lesions, study findings reveal.

HSV-2 is one of the most frequently occurring STDs, effecting approximately 16% of U.S. adults, but only 10% to 25% have recognized genital herpes.

“The risk of sexual transmission does not correlate with the recognition of clinical signs and symptoms of HSV-2, but most likely correlates with the activity of the virus on the genital skin or mucosa,” Anna Wald, MD, MPH, of the University of Washington and Fred Hutchinson Cancer Research Center in Seattle, said during a press briefing.

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More than half of patients with asymptomatic HSV-2 infections that participated in the study (60 out of 88; 68.2%) shed the virus, Wald and colleagues wrote in the April 12 issue of the Journal of the American Medical Association.

They compared rates and patterns of genital HSV shedding in 498 people who tested positive for HSV-2 and agreed to perform daily genital secretion swabs for at least 30 days between March 1992 and April 2008. The researchers used polymerase chain reaction to determine viral shedding rates.

HSV-2 was detected on 4,753 of 23,683 days in 410 symptomatic participants and on 519 of 5,070 days in 88 asymptomatic participants (20.1% vs. 10.2%; P<.001), with symptomatic patients experiencing  a median of 17.9 episodes of genital shedding per year vs. 12.5 episodes in asymptomatic patients.

Genital shedding rates also remained higher among symptomatic patients (2,708 of 20,735 days) compared with asymptomatic patients (434 of 4,929 days) during subclinical episodes (13.1% vs. 8.8%; P<.001). However, the researchers determined that the amount of HSV shed during these episodes was similar among the two groups (median 4.3 log10 copies in symptomatic patients vs. 4.2 in asymptomatic patients; P=0.27).

“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,” Wald said, adding that worries about transmitting genital herpes to sexual partners is the main source of angst among patients with the virus.

Condom use, daily valacyclovir therapy, and disclosure of HSV-2 serostatus can help reduce the risk of transmission, according to Wald. But these preventive measures have done little to reduce HSV-2 seroprevalence during the past decade, she noted, because few people with HSV-2 are aware that they have an infection.