There are eight known human herpes viruses:
- Herpes simplex I (oral-facial-ocular) and II (genital)
- Herpes viruses 6 & 7 (roseola infantum) and herpes virus 8 (Kaposi sarcoma and lymphoma)
- Varicella-Zoster, CMV, Epstein-Barr
Man is the only known natural host for Herpes simplex viruses. Herpes simplex keratitis (HSK) is a leading cause of corneal blindness worldwide. Herpes simplex ocular disease incidence is 8 cases/100,000 people/year. Incidence of all herpetic disease is 300/100,000. 50,000 cases of new or recurrent ocular disease occur each year in the US. 400,000 total Americans are afflicted.
90% of US population over the age of 15 has antibodies to Herpes simplex virus. Passive immunity is gotten from mother's antibodies up to six months of age then no longer protected. Most will get a primary infection by age five, but only 10% will have clinically evident disease.
After primary exposure, the virus lays dormant in neural ganglia (carried by axonal flow), including the trigeminal and sacral ganglia. Dormant virus has been recovered from the cornea.
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