The authors describe the investigations conducted into the first case of COVID-19 in Illinois, USA. They defined patients with confirmed COVID-19 as being those with a positive SARS-CoV-2 PCR result. Contacts were people with exposure to a case-patient on or after the patient’s symptom onset date. All contacts underwent active symptom monitoring for 14 days following their last exposure. Contacts who developed fever, cough or shortness of breath were tested for SARS-CoV-2. A convenience sample of 32 asymptomatic healthcare personnel contacts were also tested. The first case-patient was a woman in her 60s who returned from China in mid-January 2020. One week later, she was hospitalised with pneumonia and tested positive for SARS-CoV-2. Her husband (Patient 2) did not travel but had frequent close contact with his wife. He was admitted 8 days later and also tested positive for SARS-CoV-2. 372 contacts of both cases were identified; 347 underwent active symptom monitoring, including 152 community contacts and 195 healthcare personnel. Of these monitored contacts, 43 were further investigated. These 43 and all 32 asymptomatic healthcare personnel tested negative for SARS-CoV-2. Therefore in the US, person-to-person transmission of SARS-CoV-2 occurred between two people with prolonged, unprotected exposure.
Read more here