Infectious Diseases Experts

Mary K. Hayden, MD 

Director of Infectious Diseases
Mary Hayden is an expert in epidemiology, infection prevention, antibiotic resistance and emerging infectious diseases. Her recent projects have investigated factors associated with transmission of SARS-CoV-2 in healthcare settings and enterobacterales and Candida auris in long-term care facilities. She also is director of the Division of Clinical Microbiology and RUSH Medical Laboratories. She is co-principal investigator of the Regional Innovative Public Health Laboratory at RUSH.

Media Clips:
COVID-19 Testing Is Still Crucial to Ending Pandemic, Experts Say
Is a Negative COVID-19 Test Result Truly Negative?
Illinois’ First Omicron Case Detected by Special Lab at RUSH 


Mary Hayden, MD

Colleen Nash, MD, MPH

Pediatric Infectious Diseases
Colleen Nash is division chief of pediatric infectious diseases and an expert in antibiotic resistance, neonatal infections, infections in immune-compromised children and public health issues. Among her research topics are COVID-19 and the proper use of antimicrobials.

Media Clips:
Unprecedented surge in RSV cases cause Chicago area children’s hospitals to run out of beds
A new back-to-school worry for Chicago Public Schools parents: COVID’s raging Delta variant


Colleen Nash, MD

John Segreti, MD

Hospital Epidemiologist | Infection Prevention
Languages: English, Spanish

John Segreti is the medical director of infection control and prevention at RUSH. He has expertise in preventing the spread of infectious diseases, including COVID-19. He also is an expert in bone and joint infections, blood-stream infections and the use of antibiotics. 

Media Clips:
What to know about the symptoms and treatment of norovirus as it spreads across the US
Can Licking Envelopes Spread Covid-19? We Asked Experts 


John Segreti, MD