THURSDAY, Nov. 19 (HealthDay News) -- People infected with herpes simplex virus 2 (HSV-2) experience almost constant releases of small numbers of viruses from the neurons that host them into the genital tract, which may make prevention of person-to-person transmission difficult, according to a mathematical model of HSV-2 behavior described in a paper published online Nov. 18 in Science Translational Medicine.

Joshua T. Schiffer, M.D., of the University of Washington in Seattle, and colleagues used daily swabs of HSV-2 from 81 patients with herpetic genital ulcers and derived curves for viral quantities that were fitted to a mathematical model of HSV-2 pathogenesis. The model was used to estimate HSV-2 shedding frequency and herpetic lesion frequency and diameter.

The researchers found that the most realistic output from the model was produced when the amount of virus shed from neurons into the genital tract daily was assumed to be minimal. The model demonstrated that minor changes in the quantity of HSV-2 released from neurons influenced the frequency of detectable shedding. Therefore, frequent HSV-2 shedding episodes are the result of an almost constant release of small quantities of viruses from neurons in the genital tract.

"The findings of our model suggest a formidable challenge in controlling HSV shedding and person-to-person transmission. In persons infected with HSV, successful antiviral medication or immunotherapy will need to completely eliminate the frequent trickle of HSV from the neurons into the genital tract," the authors write.

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