In a blind study, 14 isolates of herpes simplex virus type 1 (HSV-1) that included nine isolates from a temporal cluster of HSV infections in a hospital Pediatric Intensive Care Unit and five unrelated isolates were analyzed by digestion of their DNA with four restriction endonucleases. These enzymes (HsuI, BglII, EcoRI, and HpaI) cleave the DNA in about 52 sites. To date, at least 16 sites have been found to be variable in the sense that they may be present or absent independently of any other cleavage site. This characteristic is stable, and no change was observed on serial propagation of the strains in culture or following repeated isolation, as long as 12 years apart, from humans. Analyses of the isolates readily discriminated between those belonging to the temporal cluster of hospital infections and the unrelated strains. They also showed that there were two independent introductions of HSV-1 into the Pediatric Intensive Care Unit resulting in two clusters of epidemiologically related infections. This type of analysis has the potential of becoming a powerful tool for tracing the spread of HSV-1 and very likely of other herpesviruses in the human population.
A series of acute herpetic infections occurred among nurses and patients in a pediatric intensive care unit (PICU). Epidemiologic study revealed two separate time clusters of infections, one in early summer and another six weeks later. Restriction endonuclease analysis of DNA extracted from virus isolates showed that each time cluster was associated with a different genetic strain of herpes simplex virus (HSV) type 1 and provided evidence of cross infection between patients and nurses. Three nurses had herpetic whitlow; the husband of one had acute gingivostomatitis; a fourth nurse had acute pharyngitis. They had no previous history of HSV infection and sequential antibody testing of affected nurses showed 19S antibody in all initially positive serums, confirming primary infection. The data provide clear evidence that PICU personnel risk acquiring serious herpetic infections from patients and vice versa unless specific precautions are taken. Restriction endonuclease analysis of HSV DNA was useful in the epidemiologic study of the infections.
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