TABLE 2.

Pairwise distances among proviral HIV-1 env sequences^a

Subject	Date(s) of samples	Comparison categoryb	No. of comparisons	% Difference
				Mean	Range
Surgeon	1995	A	10	8.2	4.3–11.4
	1996	A	6	9.6	1.2–17.0
	1995 and 1996	B	36	10.6	1.2–18.9
Surgeon’s patient	1996	A	28	5.2	1.2–9.0
Surgeon and surgeon’s patient	1995 and 1996	C	72	15.2	11.8–18.7

^aDistances between DNA sequences of the env genes from the samples described in Table 1. A matrix of pairwise DNA distances was generated by using CLUSTAL W, excluding positions with gaps and with correction for multiple substitutions. The distances are expressed as percent differences. 

^bA, comparison of sequences from the surgeon or his patient; B, comparison of sequences obtained from the surgeon at different times; C, comparison of sequences from the surgeon with those from his patient.