Harold Ginsberg, 85, a microbiologist who pioneered the study of viruses and infectious diseases, died of pneumonia Feb. 2 in Woods Hole, Mass.

Dr. Ginsberg headed the microbiology departments at Columbia University and the University of Pennsylvania, and conducted research for the National Institutes of Health. Colleagues said his work laid the foundation for the field of virology, which is the study of viruses and viral diseases.

In the 1950s, Dr. Ginsberg showed that common childhood infections such as atypical pneumonia and pharyngitis were caused by adenoviruses -- which can survive long periods outside a host. His research led to the development of vaccines.