Department of Epidemiology and Center for AIDS and STD, University of Washington, Seattle, WA.
The author would like to thank Matthew Golden for his helpful comments.
Supported by NIH/NIAID U19 AI31448 and NIH/NIAID R01 AI072728 (to L.E.M.).
Correspondence: Lisa E. Manhart, PhD, Department of Epidemiology, Center for AIDS and STD, University of Washington, 325 9th Ave, Box 359931, Seattle, WA 98104. E-mail: email@example.com.
Received for publication July 15, 2009 and accepted July 29, 2009.