Investigation and Serologic Follow-Up of Contacts of an Early Confirmed Case-Patient with COVID-19, Washington, USA

Chu, Victoria T.; Freeman-Ponder, Brandi; Lindquist, Scott; Spitters, Christopher; Kawakami, Vance; Dyal, Jonathan W.; Clark, Shauna; Bruce, Hollianne; Duchin, Jeffrey S.; DeBolt, Chas; Podczervinski, Sara; D’Angeli, Marisa; Pettrone, Kristen; Zacks, Rachael; Vahey, Grace; Holshue, Michelle L.; Lang, Misty; Burke, Rachel M.; Rolfes, Melissa A.; Marlow, Mariel; Midgley, Claire M.; Lu, Xiaoyan; Lindstrom, Stephen; Hall, Aron J.; Fry, Alicia M.; Thornburg, Natalie J.; Gerber, Susan I.; Pillai, Satish K.; Biggs, Holly M.

We describe the contact investigation for an early confirmed case of coronavirus disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), in the United States. Contacts of the case-patient were identified, actively monitored for symptoms, interviewed for a detailed exposure history, and tested for SARS-CoV-2 infection by real-time reverse transcription PCR (rRT-PCR) and ELISA. Fifty contacts were identified and 38 (76%) were interviewed, of whom 11 (29%) reported unprotected face-to-face interaction with the case-patient. Thirty-seven (74%) had respiratory specimens tested by rRT-PCR, and all tested negative. Twenty-three (46%) had ELISA performed on serum samples collected ≈6 weeks after exposure, and none had detectable antibodies to SARS-CoV-2. Among contacts who were tested, no secondary transmission was identified in this investigation, despite unprotected close interactions with the infectious case-patient.