Noteworthy are several outbreaks of human illness, in Africa, Russia, Finland, 
and Sweden, ascribed to another alphavirus closely related to SFV, Sindbis virus 
(Reviewed in: Griffin, 1986; and Acha and Szyfres, 1980). Manifestations of 
Sindbis virus infection can include fever, rash, joint pain, tendonitis, headache, 
nausea, vomiting, sore throat, periocular pain, and mild jaundice. Seropositivity 
is common in endemic regions, but overt disease is relatively unusual. 
Nevertheless, joint pain associated with Sindbis infection can persist for several 
weeks, and one case experienced an hemorrhagic rash with multiple recurrences 
over a period of four months (Guard et al. , 1982). Sindbis virus is classified for 
use at biosafety Level 2 containment (BMLB, 1988). 
2. Experimental SFV Infection 
The virulence of SFV in laboratory animals varies markedly with the strain of 
SFV employed, the age of the animal, and the route of administration. From four 
early isolates of SFV, numerous strains are available for study (Bradish, 1971). 
Mice up to 15 days of age are uniformally killed by low numbers of all strains 
of SFV (1-3 PFU/LD 5q ) administered by any route. After 15-20 days of age, mice 
become totally resistant ( > 10 7 PFU/LDso) to certain strains (A7, and derivatives), 
but are lethally infected (100 PFU/LD 50 i.p.; 1-3 pfu/LDso i.c.) by all other 
strains, including L10 (Bradish, 1971). Cause of death is acute encephalitis with 
glial and neuronal necrosis, associated with high titres of virus in the brain 
(reviewed by Griffin, 1986). 
3. Human Infections In The Laboratory and SALS Classification of SFV 
On December 7, 1977, William Scherer, Chairman of the Subcommitee on 
Arbovirus Laboratory Safety (SALS) of the American Committee on Arthropod- 
borne Viruses, wrote to several hundred laboratories worldwide summarizing the 
results (described below) of a SALS survey conducted in 1976 of safety practices 
and experience with arboviruses. Scherer included a proposed classification by 
SALS of biocontainment levels for each of the arboviruses listed, anticipating 
publication of a final set of recommendations in 1979. Among the arboviruses 
listed, SFV was recommended for biocontainment level 2, as was Sindbis virus. 
When SALS issued its final reccommendations, approximately one year later, 
however, SFV was listed at Biosafety Level 3. 
The deciding factor that changed the classification of SFV was a fatal SFV 
infection in a laboratory worker on June 16, 1978, in Tubingen, Germany 
(Willems et al., 1979). While conducting experiments with nasal innoculations of 
mice with SFV, this worker contracted a rapidly progressive encepalitis, that 
proved fatal approximately one week later. Virus isolated from the cerebrospinal 
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Recombinant DNA Research, Volume 18 
