Evaluation of virological laboratory methods for smallpox diagnosis

Area of Science:

• Virology
• Diagnostic Microbiology

Background:

• Smallpox diagnostic methods were evaluated between 1966 and 1972.
• The emergence of human monkeypox highlighted limitations in existing diagnostic techniques.

Purpose of the Study:

• To assess the sensitivity and specificity of various diagnostic methods for poxviruses, including smallpox, vaccinia, and varicella.
• To determine the adequacy of standard diagnostic approaches for emerging zoonotic poxviruses like monkeypox.

Main Methods:

• Electron microscopy
• Chick embryo chorioallantoic membrane (CAM) cultures
• Agar gel precipitation
• Tissue culture
• Rabbit dermal sensitivity test

Main Results:

• Electron microscopy was effective for varicella but only identified about half of vaccinia infections.
• CAM cultures were less sensitive in field conditions but valuable for poxvirus subgroup identification, especially with tissue culture.
• Agar gel precipitation was the least sensitive but confirmed electron microscopy results.
• Standard methods were inadequate for monkeypox diagnosis.

Conclusions:

• Electron microscopy and CAM cultures are essential for diagnosing poxviruses.
• CAM cultures are vital for vaccinia diagnosis.
• More sophisticated tests, like the rabbit dermal sensitivity test, are necessary for accurate monkeypox diagnosis.