Shedding of genital herpes simplex virus was frequent soon after first-time infection but declined significantly during the first year, based on data from 82 individuals.
Genital herpes simplex virus (HSV) infections remain common and incurable; consequently, the population with residual infection continues to rise, Christine Johnston, MD, of the University of Washington, Seattle, and colleagues wrote. However, data on the viral shedding trajectory of genital HSV-1 are limited, although HSV-1 accounts for an increasing number of infections.
In a study published in JAMA the researchers recruited 82 women with first-episode genital HSV-1 infections from sexual health and primary care clinics in Seattle, between 2013 and 2018. The participants supplied self-collected oral and genital swabs for daily HSV polymerase chain reaction testing for two 30-day periods at 2 months and 11 months after their initial symptoms. The study population was not pregnant and did not have HIV infection. The median age of the participants was 26 years, 54 were women, and 42 had primary HSV-1 infections. Primary HSV-1 infection was defined as the lack of HSV antibody at baseline or an evolving antibody profile, based on the University of Washington HSV Western Blot.
The primary outcome was the rates of genital and oral HSV shedding and lesions at 2 and 11 months and up to 2 years after an initial HSV-1 infection.
At 2 months, approximately two-thirds (64.6%) of the participants had HSV-1 in the genital tract and 29.3% had virus in the mouth. Genital shedding of HSV-1 was detected in 12.1% of 2,264 total testing days at 2 months, but this rate declined to 7.1% of 1,719 testing days at 11 months (relative risk, 0.52).
The researchers identified oral HSV-1 shedding on 3.9% of 2,247 testing days at 2 months, with a slight increase to 5.1% of 1,714 testing days at 11 months.
Both genital and oral lesions were rare, with reports of 2.6% and 0.4%, respectively, at 2 months and 3.8% and 0.5%, respectively, at 11 months.
The risk of genital shedding was significantly higher in individuals with primary HSV-1, compared with those with nonprimary infections (7.9% vs. 2.9%; RR, 2.75). The overall rate of genital shedding was 17.2% for those with primary HSV-1, of which 15.2% was asymptomatic. Oral shedding was similar for individuals with primary and nonprimary HSV in a multivariate analysis.
In addition, HSV-specific CD4+ and CD8+ T-cell responses were identified in all participants, and these remained stable during the study period. No association appeared between rates of genital and oral shedding and the proportion of cells that expressed two, three, or four cytokines.
The current study is the first known to comprehensively assess genital and oral HSV-1 viral shedding using polymerase chain reaction, the researchers wrote. “Characterizing shedding rates is clinically important because patients with genital herpes are often concerned about transmission to sexual partners, which usually occurs in the absence of lesions.”
The study findings were limited by several factors including the 22% loss of participants to follow-up by the end of the first year, and the use of data from a single location with a primarily White population, the researchers noted. Another limitation was reliance on self-reports and the potential underestimation of recurrences because of the possible use of antiviral medications between swabbing periods.
However, the results indicate the early frequency of HSV-1 shedding and suggest that suppressive therapy might benefit individuals with primary HSV-1 during their first year of infection, the researchers said.