A new study pins down the source of the 'rapid spread' of the coronavirus in China - people with little or no symptoms
- A new study estimates that 86% of COVID-19 infections in China went undiagnosed before the country's travel ban was enacted on January 23.
- People who had not been diagnosed with COVID-19 were the source of 79% of reported cases in China.
- If undiagnosed people hadn't spread the virus, the number of cases could have been reduced by 66% in Wuhan and 79% across all of China, the study reports.
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In China, an estimated 86% of COVID-19 infections went undiagnosed before the country's travel ban was enacted on January 23, according to a new study published in Science on Monday.Because there were so many undocumented cases of infection in China at that time, it was these people with undiagnosed COVID-19 coronavirus who spread it the most, leading to the "rapid spread of the virus throughout Chinam," the researchers report.
The researchers found that undocumented cases transmitted the new coronavirus about half as often as documented cases. But there were a lot more of undocumented cases. As a result, people who had not been diagnosed were the source of about eight out of every 10 infected cases in China prior to January 23.The authors - who included researchers from the MRC Centre for Global Infectious Disease Analysis at Imperial College London and collaborators from universities in New York, California, Beijing, and Hong Kong - noted that those who don't get diagnosed often have mild or even non-existent symptoms.
Consequently, these patients "can expose a far greater portion of the population to virus than would otherwise occur," the researchers wrote. They concluded that if the virus among undiagnosed people hadn't spread, the cases could have been reduced by 66% in Wuhan and 79% across all of China.
As widespread testing lags, public health officials are asking people to stay home to stop the spread of COVID-19Who does and does not get tested for the COVID-19 virus continues to be a dilemma in many parts of the world. Many jurisdictions have challenges around offering to test people, getting access to chemicals for tests, and other barriers. Many in the US who want to be tested are struggling to get access to a swab. And many of the tests distributed across the country in late January didn't work. The federal government is ramping up testing nationwide, but it's taking time to get people tested.
Canada currently has a national policy that people with no symptoms are not being tested. Prime Minister Justin Trudeau has been exposed, as his wife Sophie tested positive for the virus, but he has not been tested. He is under a self-imposed 14-day quarantine.
In the UK, however, while celebrity actor Idris Elba had no symptoms, he took a test that revealed he has COVID-19.It's this asymptomatic transmission that is why the Trump administration is asking Americans to stay home if they can, avoid groups larger than 10 people, and to stop going to public places like bars and restaurants.
During a press briefing on Monday, Dr. Deborah Leah Birx, the White House's coronavirus response coordinator, encouraged all Americans - young people in particular - to socially distance themselves in order to curb the spread of COVID-19.
"The reason we're taking these strong and bold steps is because we know there is virus spread before you develop symptoms," she said, "and then we know that there's a large group - we don't know the precise percent yet - that actually is asymptomatic or has such mild cases that they continue to spread the virus."
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