I can't make sense of the data. This update from 12th of March but the European Center for Disease Control gave this apparently conflicting statement:
Infection in asymptomatic individuals: The virus has been detected in asymptomatic persons. On a rapidly evolving cruise ship outbreak, where most of the passengers and staff were tested irrespective of symptoms, 51% of the laboratory confirmed cases were asymptomatic at the time of confirmation [33]. In Italy, 44% of the laboratory-confirmed cases have been asymptomatic [34]. In Japan, 0.06% of reported cases have been asymptomatic [35]. These proportions based on nationally notified cases likely reflect laboratory testing algorithms rather than true estimates of asymptomatic infections.
Based on Chinese data, the international WHO mission report indicates that up to 75% of initially asymptomatic cases will progress to clinical disease, making the true asymptomatic infection rather rare (estimated at 1-3%) [16].
Both viral RNA and infectious virus particles were detected in throat swabs from two German citizens evacuated from Hubei province on 1 February 2020, who remained well and afebrile seven days after admission to a hospital in Frankfurt [36]. Both a mother and a child in a family cluster remained asymptomatic (including normal chest CT images during the observation period) with qRT-PCR positive nasopharyngeal swab samples [37]. Similar viral load in asymptomatic versus symptomatic cases was reported in a study including 18 patients [38]. Persistent positivity of viral RNA in throat and anal swabs were reported in a asymptomatic female patient after 17 days of clinical observation and treatment [39].
Potential transmission from an asymptomatic person has been reported in a familial cluster of five COVID-19 patients hospitalised with fever and respiratory symptoms that had contact before their onset of symptoms with an asymptomatic family member, a young 20-year-old woman, upon her return from Wuhan [40]. She remained asymptomatic for the whole duration of laboratory and clinical monitoring (19 days).
The first paragraph confirms what you just said. Other experience in China indicates most of those initially diagnosed as infected but asymptomatic eventually show symptoms, hence the 1%-3% estimate.
I think it's a fine point and maybe I don't understand the difference in importance. Whether or not a person who is infected will show symptoms is less important than the finding that:
a) People in a closed community, i.e. a cruise ship, a nursing home, or a remote Italian village, where a large enough sample or sick and asymptomatic people have been tested, show more than 40% were infected.
b) People who are asymptomatic can infect others.
Maybe you have drawn different conclusions?
To me, what health officials are saying about what to do still holds. Don't go out. What the general public can do is slow the spread of this disease so that the health care system can continue to operate. Flatten the curve. The area under the curve is probably baked in. The spread of the curve is what we can affect by our actions.
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