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

I n December 2019, a viral pneumonia outbreak caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in Wuhan, China, before spreading rapidly to other provinces in China and then internationally (1).On January 20, 2020, the Centers for Disease Control and Prevention (CDC) confirmed a US case of coronavirus disease (COVID-19), the disease caused by SARS-CoV-2, in a traveler who had recently returned to Washington state from Wuhan (2).We investigated contacts of the confirmed case-patient to describe transmission to inform public health recommendations and control measures. MethodsWashington state and local health officials interviewed the case-patient to identify contacts and activities during time of symptom onset until appropriate isolation of the patient.Because contact investigations for COVID-19 had not been conducted in the United States, the Washington State Department of Health (WA DOH), in consultation with CDC, developed contact definitions based on the best evidence available at the time, which are not necessarily consistent with those currently in use (Table 1).We tailored the contact definitions after the case-patient interview based on the known movement and activities of the case-patient.We categorized contacts into community or healthcare contacts.For this investigation, we defined community contact as any close contact (being within 6 feet of the case-patient) for a prolonged Investigation and Serologic Follow-Up of Contacts of Early Confirmed Case-Patient with COVID-19, Washington, USA