Division of Viral Diseases Leadership Bios

Dr. Stephanie Bialek, MD, MPH

Division Director

Dr. Stephanie R. Bialek, MD, MPH, is the director of the Division of Viral Diseases in CDC’s National Center for Immunization and Respiratory Diseases (NCIRD), since 2020. Dr. Bialek, a captain in the United States Public Health Service, leads a division with 4 branches, 27 programs, and over 300 staff, fellows, and contractors.

During her career, Dr. Bialek has worked on a wide range of domestic and international public health programs. She joined CDC as an Epidemic Intelligence Service officer in 1999 and worked in the Division of Viral Hepatitis. After completing the practicum year of her residency in Preventive Medicine at the Georgia Department of Public Health in 2003, Dr. Bialek returned to the Division of Viral Hepatitis as a medical epidemiologist working on hepatitis B vaccine effectiveness and chronic hepatitis B and C.

During 2007-2008, Dr. Bialek worked in the Global Immunization Division on hepatitis B elimination. In 2008, Dr. Bialek became lead of the Herpesvirus Team in the Division of Viral Diseases. In 2015, Dr. Bialek became chief of the Parasitic Diseases Branch in the Division of Parasitic Diseases and Malaria in CDC’s Center for Global Health. Dr. Bialek has authored more than 100 peer-reviewed articles and book chapters on various infectious diseases topics. She has participated in CDC’s responses to SARS, H1N1, MERS, Ebola, and COVID-19.

Dr. Bialek received an undergraduate degree from Wellesley College, a Doctor of Medicine from New York University, and a Master of Public Health from Johns Hopkins University. She is board-certified in Internal Medicine and Preventive Medicine.


Thomas Clark, MD

Deputy Division Director

Dr. Thomas Clark obtained his bachelor’s and medical degrees at Tulane University. He trained in pediatrics at Emory University and in public health and preventive medicine at Oregon Health and Science University. He joined CDC as an EIS Officer in 2001, working in the Mycotic Diseases Branch on endemic mycoses and opportunistic fungal infections. Following EIS, he worked on bacterial zoonoses in the Meningitis and Special Pathogens Branch. Following the agency reorganization in 2006, he served as Epidemiology Team Lead and ultimately as Acting Chief for the Meningitis and Vaccine Preventable Diseases Branch (MVPDB) in NCIRD.

During his nine years in MVPDB, Dr. Clark led laboratory and epidemiologic investigations and vaccine policy development for pertussis, meningitis, and other bacterial vaccine-preventable diseases in the Division of Bacterial Diseases. He played a key role in the successful implementation and evaluation of MenAfriVac—a novel vaccine developed to end the devastating problem of epidemic meningitis in sub-Saharan Africa—and in investigating and responding to the re-emergence of pertussis. He has also led several emergency response efforts, including the first implementation of a new meningitis B vaccine during two outbreaks on college campuses, CDC’s investigation of unexplained neurologic phenomena among US Embassy staff and families in Cuba, and as the Acute Flaccid Myelitis Response incident manager. Dr. Clark joined DVD in 2018.


April Allman

Associate Director for Program Management

April Allman began her career with CDC in 1991 as a Public Health Advisor “Disease Investigative Specialist” in Lauderhill, FL with the STD and HIV programs. This involved front-line work with state and local health departments and public health clinics. In 1993 she was stationed to Memphis, TN with the Shelby County Health Department working in hospital infections and correctional facility health.

Upon accepting a position in Atlanta with the National Center for Emerging and Zoonotic Infectious Diseases (NCEZID), Special Pathogens Branch in 1996, Ms. Allman gained outbreak logistic field experience in several East African countries. She later joined the Division of Parasitic Diseases where she worked on the lymphatic filariasis elimination demonstration projects in Haiti and American Samoa. In 2003 she returned to Special Pathogens as the Branch Program Management Officer (PMO) to focus on budget, operations, and policy while continuing to provide logistics for various outbreaks and public health emergencies (Hurricane Katrina, Tulsa measles outbreak, etc.). In 2006, Ms. Allman joined DVD as Senior Advisor to the Director and attained the ADPM role in 2019.


Umesh Parashar, MD

Chief, Viral Gastroenteritis Branch

Dr. Umesh Parashar is the Chief of Viral Gastroenteritis Branch (VGB) in DVD. After completing medical training in India and the United States, Dr. Parashar joined the CDC as an Epidemic Intelligence Service (EIS) Officer in 1996 and has spent more than 20 years at CDC researching the epidemiology of viral gastroenteritis and methods for its prevention and control, including vaccination strategies against rotavirus gastroenteritis. He was the CDC co-lead of the working group that developed the recommendations for use of the new rotavirus vaccines in the United States. VGB also works with global partners to help accelerate introduction of rotavirus vaccines in developing countries with the greatest burden of rotavirus disease.

Dr. Parashar has published more than 500 scientific papers and book chapters. He has also served as guest editor on 8 supplements in scientific journals and on advisory committees to the World Health Organization. He has received several awards, including 1) the Philip R. Horne award in 2014—National Center for Immunization and Respiratory Diseases’ highest form of recognition for accomplishments and work performance that have had a significant impact on achieving the mission of the Center, 2) Emory University’s Sheth Distinguished International Alumni Award in 2014—to recognize Emory University’s international alumni who have distinguished themselves in service to universities, governments, private sector firms, and nongovernmental organizations, 3) the Oswald Avery Award for Early Achievement from the Infectious Disease Society of America in 2011, 4) the Shepard Award for Best Scientific Paper in the Prevention and Control Category from CDC in 2009, and 5) six awards for Distinguished Service from the Secretary of the US Department of Health and Human Services.


Steve Oberste, PhD

Chief, Polio and Picornavirus Laboratory Branch

Dr. Steve Oberste is Chief of the Polio and Picornavirus Laboratory Branch (PPLB) in DVD. He received a B.S. in Genetics from the University of California, Davis, in 1982, and a Ph.D. in Immunology and Medical Microbiology from the University of Florida College of Medicine, on the biochemistry of poliovirus replication in vitro. He was a postdoctoral fellow at the National Cancer Institute Frederick Cancer Research Facility in Frederick, Maryland, working on animal models for HIV and AIDS. He then spent two years at the US Army Medical Research Institute of Infectious Diseases, also in Frederick, developing vaccines and molecular epidemiological methods for Venezuelan Equine Encephalitis Virus.

In 1996, Dr. Oberste joined the Enterovirus Laboratory at CDC to lead the reference diagnostics team. He and his team developed molecular typing methods for enteroviruses and other picornaviruses that supplanted the traditional antigenic serotyping methods that were the gold standard at the time. Dr. Oberste became Branch Chief in 2012 and is responsible for overall direction and supervision of CDC’s laboratory activities in support of the Global Polio Eradication Initiative, acute flaccid myelitis, and diseases caused by non-polio human picornaviruses (other than hepatitis A virus and rhinovirus). The branch’s activities include assay development, reference diagnostics, laboratory surveillance, genomics, molecular epidemiology, population immunity, new vaccine research, vaccine clinical trials, antivirals, and virus discovery.


Aron Hall, DVM, MSPH

Chief, Respiratory Viruses Branch

Dr. Aron Hall is Chief of the Respiratory Viruses Branch (RVB) DVD. Dr. Hall earned his undergraduate and graduate degrees in Public Health from the University of North Carolina at Chapel Hill, and his Doctor of Veterinary Medicine (DVM) from North Carolina State University. Following completion of academic and clinical training, Dr. Hall joined the CDC as an Epidemic Intelligence Service (EIS) Officer and was assigned to the state health department of West Virginia.

Dr. Hall joined DVD in 2008 to lead and expand the norovirus epidemiology program and has also led efforts to respond to emerging respiratory viruses, including MERS-CoV and SARS-CoV-2. He is a recognized expert in the field, providing consultation within CDC, to state and local health departments, federal regulatory agencies, advisory committees, and international partners. Dr. Hall has authored over 150 journal articles and book chapters, has an adjunct faculty appointment at the Rollins School of Public Health of Emory University, and is board certified as a diplomate in the American College of Veterinary Preventive Medicine (ACVPM).


Paul Rota, PhD

Chief, Viral Vaccine Preventable Diseases Branch

Dr. Paul Rota is the Chief for the Viral Vaccine Preventable Diseases Branch (VVPDB) in the Division of Viral Diseases at the Centers for Disease Control and Prevention in Atlanta, GA. He is also an Adjunct Professor of Microbiology at Emory University, Atlanta, GA and at the University of Georgia, Athens, GA. He is a member of American Association for the Advancement of Science, American Society for Microbiology, and American Society for Virology.

VVPDB provides laboratory and epidemiologic support for measles mumps, rubella, and varicella/zoster control programs in the US, and laboratory support for international measles and rubella control programs. Dr. Rota is a subject matter expert for measles, mumps, and rubella and has been working in the CDC Measles Laboratory since 1991. One of his major responsibilities is to support laboratory-based surveillance for measles and rubella on a global scale. Dr. Rota works closely with WHO Global Measles and Rubella Laboratory Network and is a member of the WHO Measles and Rubella SAGE Working Group and the Regional Verification Commission for the Western Pacific Region. Dr. Rota’s main research interest is development of a microneedle patch vaccine for measles and rubella.