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1 exercises, in spite of periodic spills of these organisms 
2 and obvious infection. 
3 This experience also illustrates the well-known 
4 fact that so-called "escape" of microbes from the laboratory 
5 or infection of a laboratory worker is far from equivalent 
6 to disease production, let alone epidemic disease, which is 
7 almost unheard of as a result of laboratory infection. 
8 I would argue that a century of experience with 
9 safe handling of real pathogens should influence the 
10 requirements for handling non-pathogenic organisms containing 
11 foreign DNA whose potential pathogenicity is and always has 
12 been entirely conjectural. 
13 In regard to viruses, the proposed revisions are 
14 based on a similar principle; namely, that as a rule condi- 
15 tions used to work with a virus itself are adequate to work 
16 with recombinants containing sections of the viral genome, 
17 or even with defective virus vectors. In most instances, I 
18 might point out -- in nearly all instances -- the recommen- 
19 dations which are in the proposed guidelines in regard to 
20 virus vectors or use of bacteria to clone segments of 
21 viral DNA, generally provide for greater physical contain- 
22 ment than that ordinarily used to handle the virus itself. 
23 It is difficult to imagine how E. col i K 12 
24 containing a segment, say, of SV 40 DNA could be more 
25 hazardous than the SV 40 virion itself. Likewise, defective 
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