On October 9, 2020, this report was posted as an MMWR Early Release on the MMWR website (https://www.cdc.gov/mmwr). On May 13, 2020, the Wisconsin Supreme Court declared the state's Safer at Home Emergency Order (https://evers. wi.gov/Documents/COVID19/EMO28-SaferAtHome.pdf) "unlawful, invalid, and unenforceable,"* thereby increasing opportunities for social and business interactions. By mid-June, Winnebago County, † Wisconsin experienced an increase in the number of infections with SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19), with the largest increase among persons aged 18-23 years (young adults) (1). This age group § accounts for 12.5% of the population in the county. To identify factors that influence exposure to COVID-19 among young adults in Winnebago County, characteristics of COVID-19 cases and drivers of behaviors in this age group were examined. During March 1-July 18, 2020, 240 young adults received positive SARS-CoV-2 test results, accounting for 32% of all Winnebago County cases. In 30 key informant interviews, most interviewees reported exposure to misinformation, conflicting messages, or opposing views about the need for and effectiveness of masks. Thirteen young adults described social or peer pressure to not wear a mask and perceived severity of disease outcome for themselves as low but high for loved ones at risk. Having low perceived severity of disease outcome might partly explain why, when not in physical contact with loved ones at risk, young adults might attend social gatherings or not wear a mask (2). Exposure to misinformation and unclear messages has been identified as a driver of behavior during an outbreak (3,4), underscoring the importance of providing clear and consistent messages * h t t p s : / / w w w. w i c o u r t s. g o v / s c / o p i n i o n / D i s p l a y D o c u m e n t. pdf?content=pdf&seqNo=260868. † The COVID-19 data provided in this report are specific to the Winnebago County Health Department (WCHD) jurisdiction. Data for the portions of the City of Menasha or City of Appleton that fall within Winnebago County are not included. Data provided on the Wisconsin Department of Health Services website might be different than the information provided by WCHD because the state reports data for the entire county, which includes those portions of Menasha and Appleton. § Percentage of population includes persons aged 18-24 years in Winnebago County, Wisconsin, and were obtained using the U.S.