Worcester County District Attorney Joseph Early said during a press conference on Thursday that the person of interest is described as a Hispanic or Latino man with an athletic build, light or medium skin, and shaved or very short hair.
The man is believed to be about 30 years old and would have had scratches shortly after the murder from a struggle with Marcotte.
Police suspect the man was driving a dark-colored SUV.
"We want to do everything we can to find this killer," said Early.
Steven Therrien, Marcotte's uncle, told WBZ-TV that he hopes the DNA can help find his niece's killer.
"We're very heartened by the fact that this might ultimately be a tool that the D.A. and the State Police can use to find the person who committed this atrocious crime," said Therrien. "We hope that it happens, and we hope that it happens soon. And we hope for our friends & neighbors that this person can be taken off the streets and not harm anybody the way that he did Vanessa."
Anyone with information on the person of interest is asked to call the Massachusetts State Police tip line at (508) 453-7589.
So far, police have received more than 1,300 tips about Marcotte's death.
Early said that many have asked about a connection between Marcotte's murder and the killing of a jogger in New York City. But during Thursday's press conference, Early said that possibility has been ruled out.
"It wouldn't be the same suspect or person of interest," Early said.
D.A. Joseph Early Provides Update on Vanessa Marcotte Murder Investigation
The DNA recovered by investigators has been run through a national database, but there were no matches.
Marcotte, a Google executive and 2011 Boston College grad, was visiting from New York, and went for a run in the afternoon of August 7. Her body was found naked and burned off Brooks Station Road just a half mile from her mother's home.
Her murder shocked the small town of about 4,000.
The new break has renewed hope that police will catch the killer.
"We've been pretty discouraged that there hasn't been progress for a long time," said Hubbardston resident Roger Poluded. "I'm glad to hear that."
"The whole town is waiting for it. It's great news," said Princeton resident Lynn Dalbeck.
Though hundreds of tips have come in, nobody has been charged; in December, Marcotte's family pleaded with the public for information.
WBZ NewsRadio 1030's Lana Jones reports
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