JOIN USUS: 1st locally transmitted case of COVID-19 detailed
Scientists have detailed the first known locally-transmitted case in the US of the novel coronavirus infection, COVID-19, tracing it to a man who contracted the disease from his wife travelling from Wuhan, China.
According to the researchers, person-to-person transmission of the deadly coronavirus, SARS-CoV-2, occurred between the two people with prolonged, unprotected exposure while the first patient showed symptoms.
They said despite active monitoring and testing of 372 contacts of both cases, no further transmission was detected.
The study, published in the journal The Lancet, noted that on January 23, 2020, Illinois reported the US state Chicago's first laboratory-confirmed case, or index case, of COVID-19 in a woman in her 60s returning from Wuhan, China in mid-January, 2020.
Subsequently, the scientists said, the first evidence of secondary transmission in the US was reported on January 30, when her husband, who had not travelled outside the US but had frequent, close contact with his wife since her return, tested positive.
Following this, public health authorities conducted an intensive epidemiologic investigation of the two confirmed cases, the researchers noted in the study.
In the research, the scientists report the clinical and laboratory features of both patients and the assessment and monitoring of several hundred individuals with potential exposure to SARS-CoV-2.
In total, they identified 372 individuals as potential contacts with 347 of them actively monitored after confirmation of exposure to the woman or her husband on or after the day of symptom onset.
This included 152 community contacts, and 195 healthcare professionals, the study mentioned.
There were 25 people that had insufficient contact information to complete active monitoring, the scientists said.
They said they also tested a convenience sample of 32 asymptomatic healthcare personnel contacts.
According to the study, these 347 contacts underwent active symptom monitoring for 14 days following their last exposure.
Of these, 43 people developed fever, cough, or shortness of breath were isolated and tested for SARS-CoV-2, as well as asymptomatic healthcare professionals.
The scientists noted that all 75 individuals tested negative for SARS-CoV-2.
Assessing the data, the researchers observed that on December 25, 2019, the female patient travelled to Wuhan where she visited a hospitalised relative and other family members with undiagnosed respiratory illness.
On her return to the US on January 13, 2020, the study noted that she experienced six days of mild fever, fatigue, and cough before being hospitalised with pneumonia and testing positive for SARS-CoV-2.
Prior to hospitalisation she was living with her husband who has chronic obstructive pulmonary disease (COPD) and chronic cough, it said.
These conditions, the researchers said, made it difficult to determine the timing of his symptom onset related to COVID-19.
Eight days after his wife was admitted to hospital, the husband was also hospitalised with worsening shortness of breath and coughing up blood, and also tested positive for SARS-CoV-2, according to the study.
The scientists said both patients recovered, and were discharged to home isolation, which was lifted 33 days after the woman returned from Wuhan, following two negative tests for SARS-CoV-2 taken 24 hours apart.
"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", said Jennifer Layden, Chief Medical Officer of the Chicago Department of Public Health, US, who co-led the research.
"Our experience of limited transmission of SARS-CoV-2 differs from Wuhan where transmission has been reported to occur across the wider community and among healthcare professionals, and from experiences of other similar coronaviruses," Layden said.
She said healthcare 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.
The scientists emphasised that individuals who think they might have been exposed to COVID-19, and experiencing a fever, cough, shortness of breath, or other symptoms consistent with COVID-19 should call their healthcare provider before seeking help so that appropriate preventive actions can be taken.
They warned that without adequate protective equipment even people living together are at risk of contracting the deadly disease from their companions.
"Without using appropriate facemasks or other personal protective equipment, individuals living in the same household as, or providing care in a non-healthcare setting for, a person with symptomatic COVID-19 are likely to be at high risk of infection," said study co-lead author Tristan McPherson from the Chicago Department of Public Health.
"Current CDC recommendations for individuals with high-risk exposures to remain quarantined with no public activities might be effective in reducing onward person-to-person transmission of SARS-CoV-2," McPherson said.
The researchers, however, said these data are preliminary and note several limitations, including that the report describes only one known transmission event, therefore the findings may not be generalisable or representative of broader transmission patterns.