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Genital herpes can spread even when lesions aren't present

Largest study of herpes simplex virus type 2 to date finds asymptomatic carriers can transmit virus to partners

April 25, 2011
Dr. Anna Wald

Dr. Anna Wald and colleagues wrote, " ... 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.”

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Persons who have tested positive for herpes simplex virus type 2 but do not have symptoms or genital lesions still experience virus shedding during subclinical episodes, suggesting a high risk of transmission from persons with unrecognized HSV-2 infection, according to a study in the April 13 issue of the Journal of the American Medical Association.

Dr. Anna Wald, director of the University of Washington’s Virology Research Clinic and a researcher in the Center’s Vaccine and Infectious Disease and Clinical Research divisions, presented the findings at a JAMA media briefing at the National Press Club in Washington, D.C, earlier this month.

HSV-2 is one of the most frequent sexually transmitted infections worldwide, with global estimates of 536 million infected persons and an annual incidence of 23.6 million cases among persons aged 15 to 49 years. In the U.S., 16 percent of adults are HSV-2 positive, but only 10 percent to 25 percent of persons with HSV-2 recognize the disease.

“Most HSV-2 infections are acquired from persons without a clinical history of genital herpes,” the authors wrote. “Thus, 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,” a stage referred to as viral shedding. Shedding means the virus is replicating and therefore is transmissible to another person.

Wald, who is also a Seattle Cancer Care Alliance attending physician, and colleagues, including VIDD’s Drs. Christine Johnston, Meei-Li Huang, Amalia Magaret, and Dr. Larry Corey, Center president and director, compared the rates and patterns of genital HSV shedding in nearly 500 HSV-2-positive persons between March 1992 and April 2008. Each participant obtained daily self-collected swabs of genital secretions for at least 30 days. The rate of viral shedding was measured by sensitive DNA testing.

Among the findings of the researchers, HSV-2 was detected on 20 percent of the days in persons with symptomatic genital HSV-2 infection compared with 10 percent of the days in asymptomatic individuals. Genital HSV was detected at least once in 83 percent of people with HSV-2 symptoms and in 68 percent of people without symptoms during the two-month study.

Subclinical genital shedding rates were higher in persons with symptomatic infection compared with asymptomatic infection (13 percent versus 8 percent). “However, the median [midpoint] amount of HSV detected during subclinical genital shedding episodes was similar in persons with symptomatic and asymptomatic infection,” the authors wrote.

The researchers found that the bulk of days of shedding in persons with asymptomatic HSV-2 is unrecognized, and people may engage in sexual activity not knowing that they are at risk for transmitting the virus to sexual partners.

“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,” the authors wrote. “The issue of infectivity is both a patient management and a public health concern. The primary concern of many HSV-2-seropositive persons is the risk of transmission to sexual partners; in our experience this is the main source of angst in patients with genital herpes.”

The researchers note that condom use, daily valacyclovir therapy and telling one’s partner about the infection could halve the risk of HSV-2 transmission.

[Adapted from a JAMA news release]

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