fluid and brain tissue on autopsy revealed close similarity to the Osterrieth strain 
of SFV that was used in the experiments, both by size analysis of viral proteins 
and by virus neutralization and hemagglutination assays. 
Viewed against the three decades during which SFV had been safely employed 
in many laboratories worldwide, often with minimal containment, this exceptional 
incident raised several questions. Most important were whether the health of the 
worker was compomised in a way that predisposed her to this infection, whether 
she had received an unusually heavy innoculum, and whether the strain of SFV 
employed was unusually virulent. 
Regarding the innoculum, no useful information is available. Even whether nasal 
injection or aerosol was used to administer the virus has never been certain. 
Relatively little is known of the patient’s health or medications. In their 
published report of this incident, Willems et al. (1979) describe that she had 
endured a purulent bronchitis of one year’s duration at the time of the fatal 
infection. Further information regarding her state of health and 
immunocompetence is unavailable. 
Regarding the virulence of the SFV strain, some helpful information is available. 
According to the published report of this incident (Willems et al., 1978), the 
Osterrieth strain of SFV, prior to use in the fatal experiment, had been passaged 
extensively in animals: Following 13 passages in primary CEF cells, the virus 
was passaged 7 times intracerebrally in four- to five-week-old mice, and once 
subcutaneously in six- to seven-week-old mice. Brain material from these mice 
was then passaged four times intracerebrally in six- to seven-day-old mice, then 
once in BFIK cells. The patient worked with the supernatant of this passage. 
Multiple passage of SFV in mouse brains can be an effective means to select for 
SFV strains with increased virulence for mice (Smithbum and Haddow, 1944). 
Approximately one week after the worker died, two scientists investigating this 
incident (W.R. Willems and G.Kaluza, Institute for Virology, Giessen) compared 
the virulence of four different strains of SFV employed in the Tubingen 
laboratory, plus the virus isolated from clinical material obtained from the patient. 
Each strain was administered by subcutaneous injection (lxlO 7 pfu) into four 
mice, and the time till death was measured. A brief report of this unpublished 
study is summarized here: 
Recombinant DNA Research, Volume 18 
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