The original compounds used were 5-iodo-2-deoxyuridine, AKA idoxuridine, IUdR, or(IDU) and 1-β-D-arabinofuranosylcytosine or ara-C, later marketed under the name cytosar or cytarabine. The usage expanded to include topical treatment of herpes simplex, zoster, and varicella. Some trials combined different antivirals with differing results. The introduction of 9-β-D-arabinofuranosyladenine, (ara-A or vidarabine), considerably less toxic than ara-C, in the mid-1970s, heralded the way for the beginning of regular neonatal antiviral treatment. Vidarabine was the first systemically administered antiviral medication with activity against HSV for which therapeutic efficacy outweighed toxicity for the management of life-threatening HSV disease. Intravenous vidarabine was licensed for use by the U.S. Food and Drug Administration in 1977. Other experimental antivirals of that period included: heparin, trifluorothymidine (TFT), Ribivarin, interferon, Virazole, and 5-methoxymethyl-2-deoxyuridine (MMUdR). The introduction of 9-(2-hydroxyethoxymethyl)guanine, AKA aciclovir, in the late 1970s raised antiviral treatment another notch and led to vidarabine vs. aciclovir trials in the late 1980s. The lower toxicity and ease of administration over vidarabine has led to aciclovir becoming the drug of choice for herpes treatment after it was licensed by the FDA in 1998. Another advantage in the treatment of neonatal herpes included greater reductions in mortality and morbidity with increased dosages, which did not occur when compared with increased dosages of vidarabine. However, aciclovir seems to inhibit antibody response, and newborns on aciclovir antiviral treatment experienced a slower rise in antibody titer than those on vidarabine.
Concurrent infections, such as viral upper respiratory tract infection or other febrile diseases, can cause outbreaks. Reactivation due to other infections is the likely source of the historic terms cold sore and fever blister. Other identified triggers include local injury to the face, lips, eyes, or mouth; trauma; surgery; radiotherapy; and exposure to wind, ultraviolet light, or sunlight.The frequency and severity of recurrent outbreaks vary greatly between people. Some individuals outbreaks can be quite debilitating, with large, painful lesions persisting for several weeks, while others experience only minor itching or burning for a few days. Some evidence indicates genetics play a role in the frequency of cold sore outbreaks. An area of human chromosome 21 that includes six genes has been linked to frequent oral herpes outbreaks. An immunity to the virus is built over time. Most infected individuals experience fewer outbreaks and outbreak symptoms often become less severe. After several years, some people become perpetually asymptomatic and no longer experience outbreaks, though they may still be contagious to others. Immunocompromised individuals may experience longer, more frequent, and more severe episodes. Antiviral medication has been proven to shorten the frequency and duration of outbreaks. Outbreaks may occur at the original site of the infection or in proximity to nerve endings that reach out from the infected ganglia. In the case of a genital infection, sores can appear at the original site of infection or near the base of the spine, the buttocks, or the back of the thighs.