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bluewater

(5,376 posts) Sun Mar 22, 2020, 01:11 PM Mar 2020

A third of coronavirus cases may be 'silent carriers', classified Chinese data suggests

Source: South China Morning Post [Hong Kong]

The number of “silent carriers” – people who are infected by the new coronavirus but show delayed or no symptoms – could be as high as one-third of those who test positive, according to classified Chinese government data seen by the South China Morning Post. That could further complicate the strategies being used by countries to contain the virus, which has infected more than 280,000 people and killed nearly 13,000 globally.

More than 43,000 people in China had tested positive for Covid-19 by the end of February but had no immediate symptoms, a condition typically known as asymptomatic, according to the data. They were placed in quarantine and monitored but were not included in the official tally of confirmed cases, which stood at about 80,000 at the time.

Scientists have been unable to agree on what role asymptomatic transmission plays in spreading the disease. A patient usually develops symptoms in five days, though the incubation period can be as long as three weeks in some rare cases.
...

A growing number of studies are now questioning the WHO’s earlier statement that asymptomatic transmission was “extremely rare”. A report by the WHO’s international mission after a trip to China estimated that asymptomatic infections accounted for 1 to 3 per cent of cases, according to a European Union paper. “The number of novel coronavirus (Covid-19) cases worldwide continues to grow, and the gap between reports from China and statistical estimates of incidence based on cases diagnosed outside China indicates that a substantial number of cases are underdiagnosed,” a group of Japanese experts led by Hiroshi Nishiura, an epidemiologist at Hokkaido University, wrote in a letter to the International Journal of Infectious Diseases in February.

Based on their research, Nishiura put the proportion of asymptomatic Japanese patients evacuated from Wuhan, ground zero of the outbreak in China, at 30.8 per cent – similar to the classified Chinese government data.

Read more: https://www.scmp.com/news/china/society/article/3076323/third-coronavirus-cases-may-be-silent-carriers-classified

5 replies

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A third of coronavirus cases may be 'silent carriers', classified Chinese data suggests (Original Post) bluewater Mar 2020 OP

When the S. Koreans tested their large group, Igel Mar 2020 #1

+1 interesting points. bronxiteforever Mar 2020 #3

Which is why everyone needs testing. Chicago1980 Mar 2020 #2

I read some study yesterday that said half of cases are asymptomatic. Research shouldn't be JudyM Mar 2020 #4

If we don't test everyone RussBLib Mar 2020 #5

Igel

(35,320 posts)

1. When the S. Koreans tested their large group,

Reply to bluewater (Original post)

Sun Mar 22, 2020, 01:20 PM

Mar 2020

every man, woman, and child, that's about the percentage they found without symptoms.

Now, the question is, What percentage of cases is transmitted by asymptomatic individuals?

One reason WHO low-balled the number was the difficulty in actually identifying instances where somebody who tested positive got it from somebody who was asymptomatic.

I've been assuming that the number was about 1/3 asymptomatic and that they have about the same infectiousness as those with symptoms, based on viral load shedding data. This has been the basis for my opinion that by the time the first case was actually identified in the US, before testing was available (even the flawed CDC test), it was likely spreading in the US. And that even had there been fairly widespread (by S. Korean standards) testing in the US, containment by 1/31 was a delusion. People don't like that because it doesn't assign blame in the location and to the extent they want.

It's been pointed out since then that close contact is needed to get high rates of infection and that it's possible to shed virus in fairly large quantities without being that contagious, which makes things a bit ambiguous again.