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