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Monday, January 13, 2003Unequivocal laboratory confirmation is essential when far-reaching decisions depend on it and such diagnosis has been based on electron microscopy, gel diffusion, and egg or cell-culture inoculation, backed up in recent years by nucleic acid amplification methods. To get a reliable answer, and anything less is virtually worthless, all these methods except electron microscopy require time, mostly measured in days to complete, and all require skill and current experience in doing the procedure. Moreover, all except electron microscopy require the prompt availability of reagents or systems not now in routine use. ...Electron microscopy can provide a specific answer either way ("This is definitely a poxvirus", or "Definitely a herpesvirus") and the result can be available within 30 min from receipt of the specimen. This method, therefore, answers both requirements fully and should be the method of choice. All other techniques demonstrate, with varying but less than 100% certainty, the spoor of the virus rather than the culprit itself. Not a bad idea, although I don’t know how easy it is to distinguish the two types of viruses. Electron microscopes are much more plentiful across the nation than special virology labs. The operators would just need training to correctly identify a pox virus. And training the operators would be much cheaper than building labs. He also provides this chilling account of what could happen when the diagnosis is missed: Making a clinical diagnosis, and, in particular, differentiating smallpox from varicella, is difficult even when those concerned are seeing both diseases regularly. On at least two occasions (Knightswood, Glasgow, in 1950, and Burnley in 1956 [A W Downie, personal communication]), smallpox was incorrectly diagnosed clinically as varicella, with tragic consequences in Knightswood when 17 nurses and other contacts caught the disease and five died. Pretty sobering. UPDATE: Here’s an electron microscope image of a herpes virus and here’s the cowpox virus. posted by Sydney on 1/13/2003 08:21:00 AM 0 comments 0 Comments: |
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