Gregg Allman and Natalie Cole perform at the Tune In to Hep C benefit concert at the Beacon Theatre in New York on July 27, 2011. Both singers have battled chronic hepatitis C. Rob Bennett/AP Images for TuneInToHepC.com hide caption

itoggle caption Rob Bennett/AP Images for TuneInToHepC.com

This photo provided by the U.S. Attorney's Office in New Hampshire shows David Kwiatkowski, a former lab technician at an Exeter, N.H., hospital. AP Photo/U.S. Attorney's Office hide caption

itoggle caption AP Photo/U.S. Attorney's Office

Dr. Paul J. Pockros, a liver specialist at Scripps Green Hospital in San Diego, talks with hepatitis C patient Loretta Roberts in Jan. 2011. Lenny Ignelzi/AP hide caption

itoggle caption Lenny Ignelzi/AP