The Snowball Study (Duke RDS2: Respondent-Driven Sampling for Respiratory Disease Surveillance, the Snowball Sampling Study) has completed enrollment and is no longer enrolling study participants.

We wish to thank each of the volunteers who have taken part in Snowball, and we look forward to sharing the findings from the study as soon as they are available.

If you have any questions or would like to learn more about the Snowball study, you can contact us via email at

What Is the Snowball Study?

The Snowball Study is testing ways to identify and contact people who may have been exposed to infection by a virus such as SARS-CoV-2 (also known as coronavirus, or COVID-19). The study is led by researchers and physicians at Duke University.

How Does the Snowball Study Work?

The Snowball study uses a person’s social ties – the people they live, work, and spend time with – to trace the spread of respiratory diseases caused by viruses.

Why Are We Doing This Study?

The Snowball Study is intended to help identify people who have been infected with SARS-CoV-2 but don’t yet know it, and to learn about social activities and behaviors that affect the transmission.

Who Can Take Part in the Snowball Study?

The Snowball Study is most interested in finding people who are infected with SARS-CoV-2, also called COVID-19 or the coronavirus, but who don’t know yet that they are infected.

Why Participate in the Snowball Study?

People who choose to take part in the SNOWBALL Study will be taking an active role in helping researchers understand how respiratory diseases like COVID-19 and seasonal flu spread.


If you have any questions or would like to learn more about the Snowball study, please contact the Clinical Research Coordinator at 919-613-1239.

You can also email the Clinical Research Coordinator and the Snowball study principal investigator, Dr. Dana Pasquale, at