One of the more common viral infections affecting man is that caused by the herpes simplex virus. Its most common manifestation, the "fever blister," is so familiar to the layman that a medical diagnosis is not sought. However, the manifestations of the herpes virus are so protean that they may range from severe encephalitis, to the moderately severe stomatitis frequently seen in the very young, to the mild "fever blister" just mentioned. The more severe manifestations are due to a primary infection which occurs after an incubation period of three to five days, whereas the "fever blister" is felt to be the result of an upset in an otherwise symbiotic relationship between host and virus. Between 65% and 98% of adults, depending on areas sampled, will show neutralizing antibodies to the herpes simplex virus.
Since the initial case report of herpes simplex infection in the newborn by Haas 1 in
MITCHELL JE, McCALL FC. Transplacental Infection by Herpes Simplex Virus. Am J Dis Child. 1963;106(2):207-209. doi:10.1001/archpedi.1963.02080050209015