The study followed up with 347 contacts of a coronavirus patient to see if they developed symptoms.
The first known case of person-to-person transmission of the novel coronavirus happened while the first patient was symptomatic but exposure was prolonged and unprotected, according to research published in The Lancet.
This was the first known laboratory-confirmed case in Illinois and the United States, investigators from the US Centers for Disease Control and Prevention said. They wanted to document the case to provide details of the investigation, which involved local, state, and federal public health agencies.
A woman in her 60s visited family members in Wuhan, China who were hospitalized with undiagnosed respiratory illness. She returned to the US on January 23, 2020 and experienced 6 days of mild fever, fatigue and cough. She was hospitalized for pneumonia and later tested positive for COVID-19.
A second patient—the woman’s husband—did not travel but was reported to have frequent contact with his wife, according to the study authors. They also said that he had comorbid chronic obstructive pulmonary disease (COPD) and chronic cough, which made it difficult to determine his coronavirus symptom onset. He experienced worsening shortness of breath and coughing up blood. He was admitted to the hospital 8 days later and also tested positive for coronavirus.
The agencies identified 372 contacts of the couple. In total, 347 underwent active symptom monitoring, of which 152 were community contacts and 195 were health care personnel. There were 43 contacts who became persons under investigation (including the husband); they all tested negative for coronavirus despite developing fever, cough, or shortness of breath.
All 32 asymptomatic health care personnel tested negative for coronavirus, as well, the study authors said. They also noted that 25 people that had contact with the patient had insufficient contact information to complete active monitoring.
The husband and wife were discharged to home isolation for more than a month. The woman completed 2 negative coronavirus tests taken 24 hours apart lifting the home isolation period, which lasted 33 days.
“This report suggests that person-to-person transmission of SARS-CoV-2 might be most likely to occur through unprotected, prolonged exposure to an individual with symptomatic COVID-19,” co-lead researcher Jennifer Layden, MD, chief medical officer of the Chicago Department of Public Health, said in a statement. “Health care facilities should rapidly triage and isolate individuals suspected of having COVID-19, and notify infection prevention services and local health departments for support in testing, management, and containment efforts.”
Another study author, Tristan McPherson from the Chicago Department of Public Health, said that people who share a home with coronavirus patients are likely to be at high risk of infection themselves, especially if they are not appropriately using facemasks or other personal protective equipment. By following US Centers for Disease Control and Prevention (CDC) recommendations for these individuals with high-risk exposures, McPherson said, individuals may be able to help reduce further person-to-person transmissions.
The study authors admitted that this case was documented before the most up-to-date recommendations on self-isolation and social distancing behaviors were created. Therefore, not all of the contacts the couple made in the community may have been documented, leading to possible missed cases.
“Although further detailed reports of contact investigations of COVID-19 cases could improve our understanding of the transmissibility of this novel virus, the absence of COVID-19 among healthcare professionals supports CDC recommendations around appropriate infection control,” concluded co-lead author Isaac Ghinai from the Illinois Department of Public Health.