While not the first, the researchers report that this study uses the most sensitive techniques in a cross-sectional assessment performed to date of the presence of HSV-1 DNA in the eyes and mouths of healthy individuals, in terms of population size and total samples collected.
HSV-1, and to a lesser extent, HSV-2 are known to be the leading causes of virus-induced blindness in the Western world, with approximately 500,000 individuals having herpetic eye disease in the United States. Humans are reservoirs for herpes viruses and shedding in infected individuals when they are asymptomatic is a major factor in the transmission of the virus.
The 50 participants, who were recruited from the general population, ranged in age from 19 to 71. Nineteen were male and 31 female. African-Americans comprised 78% of the participants. The participants were asked to provide a blood sample as well as samples from twice daily swabs of their eyes and mouths for 30 consecutive days. Samples were analyzed using methods including real-time PCR, the gold standard for HSV detection in clinical samples.
Shedding was intermittent, but overall, 49 participants (98%) shed HSV-1 DNA at least once during the study. Thirty-seven participants (74%) had positive blood test results. The percentages of positive results between the eye and mouth swabs were approximately equivalent, but one measure showed higher volume in saliva than in tears. Only one participant did not shed any HSV-1 DNA. Three participants shed HSV-1 DNA in their tears but not their saliva and two had only positive saliva swabs.
Population demographics play a fundamental role in the prevalence of HSV infections. Other documented significant predictors include age, stress, socioeconomic status, level of education, age of first intercourse and total years of sexual activity. Several studies have noted an increase in herpetic disease with increased age. This could be a result of repeated infection and/or reactivation of the primary HSV infection. Also, natural stress factors such as sunlight exposure may have been a contributing factor to HSV-1 DNA shedding. UV exposure is a known trigger to activate latent HSV.
"The fact that HSV-1 DNA was discovered in such a high percentage of healthy people in the general population tells us that the virus is everywhere and it's unavoidable," said Dr. Kaufman, who developed the first effective antiviral drug for herpes infections of the eye.
In addition to Dr. Kaufman, the research team included Drs. James Hill, Hilary Thompson, Gregory Sloop, as well as Emily Varnell and Ann Azcuy. They concluded that control of virus excretion could well limit transmission, especially of more virulent strains of virus. More important, if such a high proportion of adults excrete virus, the reduction and/or prevention of virus excretion may be a simple, cost-effective way to evaluate new antiviral drugs.
The research was supported in part by a grant by the National Eye Institute and by a Senior Scientific Investigator award from Research to Prevent Blindness, Inc.
Journal
Investigative Ophthalmology & Visual Science