Herpes Colds Sores and Chicken Pox

The symptoms of infection by varicella zoster are usually unmistakable the slight fever accompanied by a rash, which tends to be concentrated on the central part of the body (the trunk) rather than on the face, arms and legs. The spots (vesicles) resemble drops of water on the skin, and these soon dry to form scabs. The infected child is inconvenienced rather than incapacitated by the infection. In adults, chicken pox can have very serious consequences, and may lead to potentially life-threatening encephalitis or pneumonia. However, the more common form of varicella zoster infection in adults leads to a condition known as shingles. This is manifested as severe inflammation of the sensory nerves, which is usually accompanied by intense pain, and later by a rash. In most instances, it seems that the varicella zoster virus of infancy has lain dormant for many decades in the nerve cells, and has been reactivated in response to some kind of trauma (perhaps depresssion or an infection), to produce an attack of shingles. 

A similar kind of dormancy between attacks is seen with HSV-1 and HSV-2 infections. Most people first encounter HSV-1 in childhood when kissed (for example) by an infected adult. In crowded conurbations, as in a town or city, well over 90% of the population may carry the virus. The virus generally causes the familiar cold sore, which begins with a small area of redness (and a tingling sensation) on the lip, and rapidly evolves into a cluster of tiny vesicles, and thence into a pustule that eventually scabs. The liquid exudate from the pustule contains highly infective virus particles. A cold sore may also occur inside the nostril or within the outer ear, and usually recurs in the same place over many decades. In between infections, the virus appears to lie dormant in nerve cells at the top of the spine. 

Its mode of action was subsequently elucidated through the use of the drug labelled with the radioactive isotopes (14C and tritium). In infected cells, 

DNA polymerases of uninfected cells were thus unaffected, even if ACV entered the cells. 

Notwithstanding these deficiencies, there is no question that acyclovir has had a major impact on the treatment of herpes infections. It is now on sale, in most countries as an over-the-counter (non-prescription) drug and as Gertrude Elion stated in her address to the Nobel Committee in 1989  

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