Herpes Simplex Virus, Type 1, HSV-1, is one of two herpes simplex infections that can infect humans. The other is Herpes Simplex Virus, Type 2, HSV-2. A general rule of thumb is that HSV-1 causes viral outbreaks above the waist, while HSV-2 infects below the waist, notes the Textbook of Bacteriology. Though general, the rule is not exclusive and each type of HSV can infect both above, as in the case of so-called cold sores, and below the waist, as in the case of genital herpes.
Herpes Simplex Virus, Type 1, Oral
A phenomenon of herpes viruses is that after infection, they establish latency. HSV-1, like HSV-2 and the herpes virus that causes chickenpox, is neurotropic, meaning that it infects nervous system tissue. After it first infects a person, and that person's immune system becomes aware of the pathogen and launches a counter-attack, the virus retreats to the nervous system, where it hides out and hibernates. In the case of oral herpes, the virus retreats to the trigeminal ganglia, a cluster of nerve cells near the ear, according to the American Social Health Association. At certain times, often in response to stress or overexposure to sunlight, the virus reactivates and returns to the skin. During subsequent infections, called recurrences, the virus can return to the original site of infection. It can however, follow nerve pathways to other, nearby sites, including the mouth, chin, nose, cheeks and eyes.
Herpes Simplex Virus, Type 1, Genital
While HSV-2 causes the majority of genital herpes outbreaks, according to the Centers for Disease Control and Prevention, HSV-1 proves responsible for about 10 percent. HSV-1 genital herpes can become transmitted during oral-to-genital sex, or during genital-to-genital sex with a person already infected with HSV-1 in the genital area. HSV-1 genital infections usually prove less active than HSV-2 infections in the area.
Herpes Simplex Virus, Type 1, Ocular
The University of Illinois Medical Center's Department of Ophthalmology reports that some 25 million people experiences recurrences of oral, or facial, herpes each year. Occasionally, HSV-1, when it reawakens, travels not to the original site of infection, but to the eye. When it does, it will more likely occur only in one eye. When this happens, the cornea, the clear cover of the eye, is usually the area affected, though infection can go deeper. An ocular herpes infection can cause faulty or blurred vision, sensitivity to light, pain, and loss of vision or even blindness.
Neonatal Herpes
Herpes can transfer from a mother to baby during vaginal delivery. The University of Washington Academic Medical Center, UWAMC, reports that 2 out of 1,000 mothers are HSV positive at the time of delivery, even though most mothers are asymptomatic. When a baby becomes infected during delivery, a range of serious complications, including seizures and shock, can occur. Eighty percent of babies infected during birth die as a result of the infection. UWAMC reports that the majority of those who survive will become seriously impaired.
