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Volume 11, Number 11—November 2005

Adventitious Viruses and Smallpox Vaccine

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To the Editor: Recently, Murphy and Osburn (1) strongly argued for testing old smallpox vaccine stocks made in animal skin for adventitious infectious agents such as viruses, mycoplasmas, and eventually, prions. Their argument appears clearly justified after unexpected cases of myopericarditis occurred during recent campaigns of smallpox vaccinations in the United States (2).

To the long list of bovine viruses cited in this paper, it seems necessary to add another, the pseudocowpox virus, a widespread parapoxvirus that may infect humans. During the 1960s, this virus was identified in vaccine lymph from a heifer at the Institut Pasteur, Paris (3).

In humans, this virus is responsible for limited skin lesions, more frequently in immunocompromised patients. Mainly farmers and butchers are affected. Pseudocowpox virus is easily differentiated from orthopoxviruses such as vaccinia virus by the virus's peculiar form on transmission electron microscopy scan, but polymerase chain reaction is probably the best detection method (4). In fact, many other more hazardous viruses may be found in the oldest stocks of smallpox vaccine and deserve more attention than previously considered.


Claude Chastel*Comments to Author 
Author affiliation: *Virus Laboratory, Brest, France



  1. Murphy  FA, Osburn  BI. Adventitious agents in smallpox vaccine in strategic national stockpile. Emerg Infect Dis. 2005;11:10869.PubMedGoogle Scholar
  2. Arness  MK, Eckart  RE, Love  SS, Atwood  JE, Wells  TS, Engler  RJ, Myopericarditis following smallpox vaccination. Am J Epidemiol. 2004;160:64251. DOIPubMedGoogle Scholar
  3. Pournaki  R, Vieuchange  J, Lépine  P, Fasquelle  R. Isolement d'un virus distinct du virus vaccinal au cours de passages d'une lymphe vaccinale de génisse. Ann Inst Pasteur (Paris). 1964;107:17383.PubMedGoogle Scholar
  4. Inoshima  Y, Morooka  A, Sentsui  H. Detection and diagnosis of parapoxvirus by the polymerase chain reaction. J Virol Methods. 2000;84:2018. DOIPubMedGoogle Scholar


Cite This Article

DOI: 10.3201/eid1111.051031

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Table of Contents – Volume 11, Number 11—November 2005


Please use the form below to submit correspondence to the authors or contact them at the following address:

Claude Chastel, Laboratoire de Virologie, Faculté de Médecine, F-29 200, Brest, France; fax: 33-2-98-01-64-74; email:

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