He took a residency in pathology, as well as training in molecular biology, at Yale University, then went to work at the National Institutes of Health.
He has been a professor at the University of California, San Diego, a consulting pathologist at the National Cancer Institute, and director of anatomic and molecular pathology at Cedars Medical Center in Miami, Florida.
[2] He co-wrote the chapter on coronaviruses in the book Comprehensive Virology[3] and has published extensively on the subject.
[4][5] In February 2020, he wrote a "Dear colleagues" open letter detailing his advice on how to avoid contracting COVID-19 and similar diseases.
In March 2020, this open letter received multiple on-line re-postings and obtained wide attention.