Board of Directors

Executive Leadership
Board of Directors
Medical Directors

Board of Directors

Taejoon Ahn, MD MPH CPE
President/Chief Executive Officer
Board Chair

Read Dr. Ahn's bio

Taejoon Ahn, M.D. became the president of John Muir Medical Group (JMMG) in January of 2014. He oversees a medical group of over 300 clinicians, mostly in primary care. JMMG is the exclusive contracted provider of primary care services for John Muir Health, partnering closely for over 20 years. Prior to the presidency, Dr. Ahn served as vice president and medical director of urgent care services for JMMG. He also worked as faculty for the University of California, San Francisco's National HIV/AIDS Clinicians' Consultation Center. He is currently an Assistant Clinical Professor of Family & Community Medicine for UCSF.

Dr. Ahn also serves as director on the board of John Muir Health as well as the board of Canopy Health. Canopy Health is a joint venture between multiple provider groups to offer a large network in the San Francisco Bay Region.

Dr. Ahn received his medical degree from the University of California San Francisco, where he also completed a residency in Family & Community Medicine. He received his Masters in Public Health with an emphasis in Epidemiology from UC Berkeley. He is an alumnus of the California Healthcare Foundation's Leadership Fellowship and is a certified physician executive with the American Association for Physician Leadership (formerly the American College of Physician Executives).

Kishore Nath, MD
Associate Program Director
Family Medicine
Residency Program
Board Vice Chair

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Kishore Nath, MD has been with John Muir Medical Group since October 2009 practicing Family Medicine. As the Medical Director of John Muir Health’s free mobile health clinic since 2010, Dr. Nath has actively pursued his passion for providing care to the vulnerable and underserved. In 2016 he joined the John Muir Health Family Medicine Residency Program, as their first Core Faculty member. Helping develop and implement the John Muir Health Residency program has been a fruitful experience combining his love of teaching and research with high quality patient care.

Dr. Nath is an assistant professor of Family and Community Medicine with UCSF. He is also a Clinical Adjunct Professor of Family Medicine at USC’s Keck School of Medicine, and Adjunct Assistant Professor with Touro University.

Dr. Nath received his undergraduate education at the University of California, Berkeley then returned home to attend medical school at the University of Southern California, Keck School of Medicine and completed his Internship and Residency at Long Beach Memorial Medical Center. He served as Chief Resident from 2000-2001 and received the resident teacher award in 2001 upon graduation from the Society of Teachers in Family Medicine. He is a graduate of the University of California, San Francisco Faculty Development Fellowship as well. Dr. Nath is board certified in Family Medicine.

Born and raised in Southern California, he remains a devoted Dodgers and Lakers fan. He enjoys watching his kids grow and tries to return to the beach whenever he can. Dr. Nath is currently working on a project to bring supplies and evidence based training to a medical clinic on the outskirts of Arequipa, Perú. Service to patients at home and abroad is invigorating for Dr. Nath and teaching the next generation of physicians to serve with humility and enthusiasm is his small contribution to the John Muir Health community.

Michael Schierman, MD
Medical Director Recruitment
Board Secretary

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Dr. Michael Schierman has been working in the San Ramon/Danville area for over 25 years. He and his wife, Suedale, moved to California in 1992 from Calgary, Alberta after completing his Family Medicine Residency at Foothills Hospital, University of Calgary. Dr. Schierman attended the University of Calgary to complete both his undergraduate degree in Psychology and Medical degree, then completed an Internship year at McGill University in Montreal, Quebec.

Dr. Schierman was initially recruited to practice Family Medicine by the San Ramon Medical Center in 1992. He has served in several leadership roles with this institution including Vice Chief of Staff, Secretary Treasurer and Head of Family Medicine. Early in his career, as a member of Hill Physicians, he participated in committee work. As time passed, he became an exclusive member of the Muir Medical Group IPA and served on their Executive Committee as the Vice President and briefly as interim President. Throughout his career with the IPA, he served on a number of IPA and John Muir Health Network committees and represented the IPA on the Network Board.

Dr. Schierman joined John Muir Medical Group in 2012 and is currently the Medical Director for Recruitment and serves on the Compensation committee. Dr. Schierman is also in full-time Family Practice in Danville, CA working with Dr. Christine Chang and Dr. Priya Swamy.

Outside of medicine, he enjoys being a loving husband to Suedale, his wife of 32 years, and also being a great dad to kids, Matt, 20 and Michaela, 18. Musically inclined, Dr. Schierman, plays guitar and enjoys helping Suedale with their church music program. He enjoys getting together with friends, working out and travelling. You may see Dr. Schierman in the Danville July 4^th parade as a "semi-professional" Elvis impersonator.

Bibanjeet Virk
Medical Director Hospitalist
Board Director at Large

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A dedicated hospitalist leader with 15 years of frontline experience bringing deep clinical insight, extensive expertise in healthcare governance, strategic foresight, operational excellence and leadership and unwavering professional integrity to the Board of Directors. Stepping into her role as Board Director at Large, where she chairs the Risk Committee and serves on the Executive and Finance Committees, she leverages her robust clinical background and analytical oversight to champion fiscal responsibility, mitigate organizational risk, and drive balanced, sustainable growth for the medical group.

Dr. Virk's education and professional credentials include:

Certification: Board Certified, American Board of Internal Medicine (ABIM)

Residency: St. Vincent’s Medical Center (Affiliated with UConn), Bridgeport, CT

Medical School: MBBS (Bachelor of Medicine and Surgery), KMC, Manipal Academy of Higher Education, Mangalore, Karnataka, India

Outside of her clinical and governance responsibilities, Dr. Virk enjoys painting with acrylics, cooking and baking. A dedicated soccer and tennis mom, she spends most of her free time cheering on her kids at local practices, games, and tournaments.

Karen Sonnenthal, NP
Director NP/PA and NP/PA Student Coordinator

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Karen L. Sonnenthal has been with John Muir Medical Group since 1997, joining the group after graduating with a Masters in Nursing Science from Oregon Health Sciences University.

Born in California, Karen grew up in Baltimore Maryland, then moved to Oregon where she attended the University of Oregon and received an undergraduate degree in Biology and Psychology.

Karen is currently working as a Family Nurse Practitioner, and is the Associate Medical Director for the NP/PA group within John Muir Medical Group. She is also a member of the Quality and Compensation Committees.

Outside of work she enjoys hiking, gardening and reading as well as spending time with her boys—husband Eric, son Nate, and 2 fur pups Luca and Max.

Rami G. Fasheh, MD
Medical Director of Inpatient Quality

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Rami G. Fasheh MD, has been with John Muir Medical Group since 2013. He is a board-certified Family Medicine physician and the Medical Director of Inpatient Quality at John Muir Health where he has served patients and families for the past eight years, receiving the Top Hospitalist award in 2015.

In his practice, Dr. Fasheh is committed to improving the health of his patients and their communities with quality and compassion. He also teaches medical residents at the UCSF/Family Medicine Residency Program at John Muir Health.

Dr. Fasheh holds a Bachelors’ Degree in Chemistry, minoring in Biology and Mathematics from the University of Louisville and a Medical Degree from the School of Medicine at the University of Dublin, Trinity College. He completed his Family Medicine Residency at Deaconess Hospital in Evansville, Indiana and a Hospital Medicine fellowship at St. Mary’s Medical Center. Dr. Fasheh is also an alum of the Alameda County’s Physician Leadership Program.

In his free time, Dr. Fasheh enjoys hiking, traveling, exercise and spending time with family and friends.

Robin Meezan, MD
Medical Director Pediatrics and Medical Student Coordinator

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Robin Meezan was born and raised in Napa Valley. She went to college at Stanford University where she received a BA in Human Biology. Dr Meezan attended the University of Alabama School of Medicine for her MD and completed her pediatric residency at UCSF Benioff Children's Hospital Oakland. In 2006 she started as a pediatrician in Berkeley, and in 2013 she became a partner with John Muir Medical Group moving her practice to Orinda. Robin Meezan lives with her husband and two children in Orinda, she enjoys making pottery, cooking projects, tending to her fruit trees, and hiking all around the Bay Area.

Dr Meezan enjoys building relationships with parents caring for infants all the way through the teenage years. She has a special interest in helping with sleep and nutrition at all ages. She is the Medical Director for Pediatrics and the Medical Student Liaison for John Muir Medical Group.

Neeta Milasincic, MD
Medical Director Inpatient Services

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Dr. Milasincic is a physician-leader and academic hospitalist with 25 years of experience across ambulatory and inpatient care, with a focus on geriatrics. She earned a B.S. in Electrical Engineering from Baylor University and an M.D. from Baylor College of Medicine, then completed an Internal Medicine residency at Christiana Care Health System. She went on to hold leadership and teaching roles, including Assistant Chief of Staff for the Department of Medicine, Director of the fourth-year student program, and residency faculty member, and also held an appointment as a Clinical Assistant Professor at Sidney Kimmel Medical College. Dr. Milasincic is a Fellow of the American College of Physicians and formerly served as Mid-Atlantic Regional President of the Society of General Internal Medicine (SGIM).

Since joining John Muir Medical Group in 2017, Dr. Milasincic has advanced hospital operations as Hospitalist Medical Director and provided first-line care for hospitalized COVID patients, helping guide respiratory isolation unit workflows during the pandemic. She led development of the geriatric trauma consult service and continues to serve as the Geriatric liaison to the trauma program. Dr. Milasincic is Chair of Hospital Medicine at John Muir Health (Concord) and a Director on the John Muir Medical Group Board of Directors.

Alice Brock-Utne, MD
Pediatrics

Caroline Schreiber
Family Medicine

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Dr. Caroline Schreiber joined John Muir Medical Group in 2018 as Medical Director for the Berkeley Oakland Region after prior experience at Stanford Healthcare managing a medical practice and serving on the Board of Directors. She currently serves as Executive Medical Director of Ambulatory Health. She enjoys the full variety of patients, illnesses and procedures that family medicine offers, particularly pediatrics, adolescent medicine, women’s health and sports medicine.

A third-generation physician, Dr. Schreiber completed her undergraduate at Harvard where she received an AB cum laude in Anthropology. She received her medical degree at the University of Michigan in Ann Arbor. Dr. Schreiber completed her Family Medicine training at Sutter Family Medicine Residency in Sacramento, where she served as Chief Resident in her final year and went on to join the faculty, continuing to teach residents.

A native of Oakland, Dr. Schreiber, is rooted in the Bay Area. In her free time, Dr. Schreiber enjoys playing soccer, cycling, spending time with her family, and watching the Valkyries and Warriors.

Ethan Hollander, MD
Urgent Care

Read Dr. Hollander's bio

Dr. Hollander joined John Muir Medical Group in 2003, practicing in a busy urgent care/family medicine outpatient office serving both adults and children. He enjoys providing a range of services from continuity care of chronic diseases to urgent issues such a upper respiratory infections, orthopedic injuries, lacerations, outpatient gynecology, pediatric issues, and many other acute illnesses. Dr. Hollander first served on the JMMG Board of Directors from 2016 to 2025. When his Board term ended in April of 2025, the Board of Directors nominated him to serve as Partner Member at Large and subject matter expert for JMMG Finance and Partner Management, and Board Observer. When the call came out for Board Directors in the fall of 2025, Dr. Hollander knew he wanted to continue to serve the Group.

Dr. Hollander earned undergraduate degrees in both Philosophy and General Biology from the University of California at San Diego, graduating Cum Laude. He attended Medical School at the University of California at Davis. While in school, he volunteered at a community clinic serving uninsured patients in Sacramento. In addition, he was a member of the ethics committee and participated in Habitat for Humanity building projects. He completed his residency at Harbor Family Practice – University of California at Los Angeles. Dr. Hollander is board certified in Family Practice.

Dr. Hollander’s interests include literature, music, biking, camping and good food. He has lived in both England and New Zealand, each for one year, and has traveled numerous occasions to Thailand, Europe, Costa Rica and Mexico.

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