Abstract
Diagnostic electron microscopy (DEM) was an essential component of viral diagnosis until the development of highly sensitive nucleic acid amplification techniques (NAT). The simple negative staining technique of DEM was applied widely to smallpox diagnosis until the world-wide eradication of the human-specific pathogen in 1980. Since then, the threat of smallpox re-emerging through laboratory escape, molecular manipulation, synthetic biology or bioterrorism has not totally disappeared and would be a major problem in an unvaccinated population. Other animal poxviruses may also emerge as human pathogens. With its rapid results (only a few minutes after arrival of the specimen), no requirement for specific reagents and its “open view”, DEM remains an important component of virus diagnosis, particularly because it can easily and reliably distinguish smallpox virus or any other member of the orthopoxvirus (OPV) genus from parapoxviruses (PPV) and the far more common and less serious herpesviruses (herpes simplex and varicella zoster). Preparation, enrichment, examination, internal standards and suitable organisations are discussed to make clear its continuing value as a diagnostic technique.
Highlights
There used to be a criticism of diagnostic virology that by the time the result was known the patient was either dead or better
This paper presents the possibilities and advantages of Diagnostic electron microscopy (DEM)
1, other conditions—both infective anxiety that would follow the reappearance of a variola-like disease, it would be necessary for health and non-infective—may resemble smallpox to a greater or lesser extent
Summary
There used to be a criticism of diagnostic virology that by the time the result was known the patient was either dead or better. In the 1960s, before smallpox had been eradicated from the world, an adult male was found in the busy out-patient department (OPD) of a major London hospital late on a Friday where he had been all afternoon. Other viruses cause vesicular lesions which may mimic smallpox. Generalised vesicular rash with large deep-seated vesicles all at the same stage, dimpled at the centre developing into pustules and crusting over later. Occasionally transmitted to man Usually single vesicular or papular lesion, developing into ulcer, and crusting later. There are poxviruses native to animal species, some of of which may infect man but without causing an epidemic. OPV virions are large by virus standards and are brick-shaped with short surface protrusions
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