SARS-CoV-2 Coronavirus Outbreak in the USA
Sustained coronavirus person-to-person transmission has not been observed in the USA during 2020
Since December 2019, an outbreak of coronavirus disease 2019 (COVID-19), has been impacting the world’s health status and economies.
According to the US Centers for Disease Control and Prevention (CDC) report on March 3, 2020, the disease spread widely in China, and, as of February 26, 2020, COVID-19 disease cases had been identified in 36 other countries and territories, including the USA.
Person-to-person transmission of the coronavirus SARS-CoV-2 has been widely documented, and a limited number of countries have reported sustained person-to-person spread.
On January 20th, state and local health departments in the USA, in collaboration with teams deployed from CDC, began identifying and monitoring all persons considered to have had close contact† with patients with confirmed COVID-19.
The aims of these efforts were to ensure rapid evaluation and care of patients, limit further transmission, and better understand risk factors for transmission.
As of February 26th, 12 travel-related COVID-19 cases had been diagnosed in the USA, in addition to 3 COVID-19 cases in patients with no travel history and 46 cases reported among repatriated U.S. citizens.
Following confirmed diagnosis, the 12 patients with travel-related COVID-19 were isolated in the hospital if medically necessary, or at home, once home care was deemed clinically sufficient.
Among the first 10 patients with travel-related confirmed COVID-19 reported in the USA, a total of 445 persons (range = 1–201 persons per case) who had close contact with one of the 10 patients on or after the date of the patient’s symptom onset were identified.
- Nineteen (4%) of the 445 contacts were members of a patient’s household, and five of these 19 contacts continued to have household exposure to the patient with confirmed COVID-19 during the patient’s isolation period;
- 104 (23%) were community members who spent at least 10 minutes within 6 feet of a patient with the confirmed disease;
- 100 (22%) were community members who were exposed to a patient in a health care setting; and
- 222 (50%) were health care personnel.
During the 14 days of active symptom monitoring, 54 (12%) close contacts developed new or worsening symptoms deemed by local public health authorities to be concerning for COVID-19 and were thus considered persons under investigation (PUIs) and subsequently were tested for SARS-CoV-2.
Two persons who were household members of patients with confirmed COVID-19 tested positive for SARS-CoV-2.
This yielded a symptomatic secondary attack rate of 0.45% (95% confidence interval [CI] = 0.12%–1.6%) among all close contacts, and a symptomatic secondary attack rate of 10.5% (95% CI = 2.9%–31.4%) among household members.
Both persons with confirmed secondary transmission had close contact with the respective source patient before COVID-19 was confirmed and were isolated from the source patient after the patient’s COVID-19 diagnosis.
No other close contacts who were tested for SARS-CoV-2 had a positive test, including the five household members who were continuously exposed during the period of isolation of their household member with confirmed COVID-19.
An additional 146 persons exposed to the two patients with secondary COVID-19 transmission underwent 14 days of active monitoring.
Among these, 18 (12%) developed symptoms compatible with COVID-19 and were considered PUIs.
All tested negative, and no further symptomatic COVID-19 cases (representing tertiary transmission) have been identified.
In the USA, two instances of person-to-person transmission of SARS-CoV-2 have been documented from persons with travel-related COVID-19 to their household contacts.
Since February 28th, an increasing number of newly diagnosed confirmed and presumptive COVID-19 cases have been in patients with neither a relevant travel history nor clear epidemiologic links to other confirmed COVID-19 patients.
However, despite intensive follow-up, no sustained person-to-person transmission of symptomatic SARS-CoV-2 was observed in the United States among the close contacts of the first 10 persons with diagnosed travel-related COVID-19.
Analyses of the timing of exposure during each patient’s illness as well as the type and duration of exposures will provide information on potential risk factors for transmission.
Infection control and prevention efforts by patients with COVID-19, their household members, and their health care providers, in combination with contact tracing activities, are important to mitigate community spread of the disease.
Furthermore, as of March 3, 2020, the CDC has not recommended any preventive vaccine for this novel coronavirus nor therapeutic treatment for the COVID-19 disease.
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