The FBI is monitoring the investigation into the disappearance of a Harvard biologist because of his research into potentially lethal viruses, including Ebola.

Dr. Don C. Wiley, 57, was last seen in Memphis, Tenn., where he attended the annual meeting of the Scientific Advisory Board of the St. Jude Children's Research Hospital. His car was found on Nov. 16 on a bridge over the Mississippi River, with a full fuel tank and the key in the ignition.

Wiley had left the Peabody Hotel just four hours before the rental car was discovered. He was supposed to have met his wife and two children that same day in Cambridge, Mass.

FBI agents took an interest in Wiley's disappearance because of his expertise and "given our state of affairs post-Sept. 11," FBI agent William Woerner in Memphis told The Boston Globe.

Wiley, a Harvard biochemistry and biophysics professor, is considered a national expert on Ebola, HIV and influenza. Ebola is a highly contagious virus that kills 50 to 90 percent of its victims; there is no vaccine.

In 1999, Wiley and another Harvard professor, Dr. Jack Strominger, won the Japan Prize for their discoveries of how the immune system protects humans from infections.

Wiley's wife, Karen Valgeirsdottir, doesn't think his disappearance is related to his work because most of it is available in books and on the Internet.

"That just doesn't seem plausible," she said.

Wiley's sister-in-law, Susan Wiley, who lives in the Memphis area, has said it is uncharacteristic for Wiley not to leave a note. Days before his disappearance, he left a note for his 85-year-old father telling him when he planned to return from a jog, she said.