All of our highly specialized providers currently on staff are American Academy HIV Specialist (AAHIVS) certified, or training for the certification. They are constantly looking for ways to promote our services and hone their skills, conducting research and attending conferences and meetings. Together, they work to create a pertinent conversation on the developments of HIV and hepatitis. The program has grown rapidly from a single provider in 2011 to several HIV and hepatitis C specialists working at four separate locations in Riverside County and San Bernardino County. Their compassionate approach to treatment is well regarded by our patients.


If you would like to make an appointment, please call (760) 676.5800.

Clayton Barbour, MD

Medical Director of Specialty Services

Dr. Clayton Barbour graduated from the University of Miami School of Medicine in 1982 and subsequently completed his postgraduate medical education at the University of Florida School of Medicine. During his professional training in Miami, he was involved with caring for some of the first AIDS patients in the United States. In 1984, Dr. Barbour was one of the founding members of the AIDS Coalition Duval County, and then, almost a decade later, he established a practice at Davies Medical Center in the Castro District in San Francisco. There, he also served on the HIV Services Committee and the Community Consortium of Bay Area HIV Health Care Providers.


From September 1994 to June 2011, he served as the Medical Director for Desert AIDS Project’s HIV Health Center in Palm Springs. In his current position as the Medical Director of Specialty for Borrego Health, Dr. Barbour has been instrumental in redefining a medical program for the treatment of HIV/AIDS and chronic hepatitis C.

Gennady "Henry" Nosovitsky, PA-C

Medical Provider


Joined Borrego in June 2016. Specializes in the management of HIV (including PrEP and PEP), HIV/Hepatitis B Co-infection, Hepatitis C and sexual health (including the treatment of sexually transmitted infections, such as syphilis, gonorrhea, chlamydia, etc.).

Robert Fontanilla, PA-C

Medical Provider


Before earning his master’s degree as a certified physician assistant from Touro University California, Robert Fontanilla had a successful career in the pharmaceutical industry for many years, holding various positions, including Executive Account Consultant for HIV products. For his degree, Robert completed his clinical training at Indian Health Services, Dallas Methodist Medical Center, and various private practices in California, Arizona, and Texas. In addition to his role as a physician assistant, he holds a master’s in Public Health, with an emphasis in Global Health and completed his field study at a community hospital in Sucre, Bolivia, where he was involved in health education for patients and providers.


Upon joining Borrego Health Specialty Clinic, he began specializing in the treatment of hepatitis C, HIV, and trans people. He lectures for Marshall B. Ketchum University and California Baptist University physician assistant programs and serves as a preceptor, teaching future medical providers about specialty health and patient care. Robert has presented for many conferences, county public health departments, and is a faculty member for Gilead Sciences.   


Robert is a member of the Phi Theta Kappa academic honor society, the California Academy of Physician Assistants, American Academy of Physician Assistants, and American Academy of HIV Medicine.

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Ashraf Zadshir, MD

Director of Residency and Medical Education


Dr. Zadshir is the founder and Director of the Department of Residency and Medical Education of Borrego Health. She is a clinical assistant professor of family medicine at the Keck School of Medicine of the University of Southern California and clinical associate professor at the School of Medicine of St. George's University. In Addition, she is the EMC-FMR Assistant Program Director.


A native from Iran, Dr. Zadshir attended the Heinrich Heine University in Dusseldorf, Germany where she graduated with a medical degree. After that, she started her post-graduate training in internal medicine and rheumatology. In 2008, after completing her Family Medicine Residency Program at USC, she joined Borrego Health and, in 2009, became Borrego Health's Regional Medical Director for Riverside County. In 2012, Dr. Zadshir founded the Department of Residency and Medical Education at Borrego Health establishing a unique collaboration of Borrego Health with multiple residency programs  Riverside.

Daniel Pearce, DO, BS

Medical Provider


Dr. Daniel Pearce graduated with a Bachelor of Science degree in Biology, Honors in Research from the University of California, Irvine and with his medical degree from the College of Osteopathic Medicine and Surgery, Des Moines and then completed 4 years of training, graduating from his Internal Medicine Residency at Wayne State University, Detroit where he saw his first HIV patient in 1983.  He worked in the Michigan Department of Corrections and then in multiple rural areas of the Dominican Republic where he learned Spanish. In San Diego, he completed an AIDS Mini-Residency at the University of California’s Owen Clinic in 1988. 


He then moved on to Los Angeles as the Director of Research for AltaMed, and then Pomona—where he was an Associate Professor of Medicine at Western University of Health Sciences while being a hospitalist at Arrowhead Regional Medical Center.  He then moved to the Department of Public Health for Riverside County as the main HIV specialist, and then to Borrego Health in San Bernardino, Riverside, and San Jacinto. He relieves the hospitalist on vacation at Malamulo Hospital, Malawi each year for a couple of weeks since 2011.


Dr. Pearce is a Clinical Associate Professor of Medicine at Loma Linda University and an Adjunct Professor of Internal Medicine and HIV at two institutions: Touro University-California College of Osteopathic Medicine and Midwestern University Arizona-College of Osteopathic Medicine. He has completed a national and two California academic clinical trial courses and has performed many clinical trials resulting in being the primary or co-author of 31 abstracts or posters, and 23 journal publications.  He has written a monthly medical column for a Latino gay men’s publication for over 10 years.


Making sure each patient is heard and that their needs are met is a priority for him.