Dr. Karl Habel, 73, a retired chief of the laboratory of infectious diseases and the biology of viruses at the National Institutes of Health, died Friday at the Manor Care nursing home in Wheaton following a heart attack.

Dr. Habel, who was born in Philadelphia, graduated from the University of Pennsylvania and earned his medical degree at the Jefferson Medical College. He joined the Public Health Service and moved to Washington in 1938, when he began his career at NIH. A pathologist by training, his career was in research and administration in that field. He was a rabies expert with the World Health Organization.

In 1967, when he retired from the PHS and NIH, he joined the staff of the Scripps Clinic and Research Foundation in La Jolla, Calif. He also taught at the University of California Medical School at San Diego. He retired in 1970 for reasons of health.

Dr. Habel received the Public Health Service's Distinguished Service Medal and the R. E. Dyer Lectureship at NIH in 1966.

He was a member of the American Academy of Microbiology, the Washington Academy of Medicine and other learned societies.

His wife, the former Ruth Carter, died in 1970.

Dr. Habel, who returned to the Washington area earlier this year, is survived by a daughter, Grethchen Hill of Rockville; a son, Kurt of Derwood, Md.; a sister, Claire Piltz of Hanover, Pa.; and five grandchildren.