https://blogs.bmj.com/bmj/2020/05/04/...
Between 5% and 80% of people testing positive for SARS-CoV-2 may be asymptomatic
Symptom-based screening will miss cases, perhaps a lot of them
Some asymptomatic cases will become symptomatic over the next week (i.e. pre-symptomatic)
Children and young adults can be asymptomatic
There is not a single reliable study to determine the number of asymptotics
Population based antibody testing required
Diamond Princess
https://www.ncbi.nlm.nih.gov/research...
3,711 people tested
634 tested positive
18%
Vo’Euganeo, (50Km west of Venice)
https://www.bmj.com/content/368/bmj.m...
All 3,000 people in village tested
50 – 75% asymptomatic
Asymptomatics infectious
represented ‘a formidable source’ of contagion
328 adults in Shanghai
https://www.clinicalmicrobiologyandin...
328 adults were diagnosed with COVID-19 in Shanghai
Among them, 13 patients were asymptomatic at time of diagnosis
No subjective symptoms 2 weeks before admission
All of the 13 (4%) them were close contacts of the confirmed cases
Japanese nationals evacuated from Wuhan
https://www.ijidonline.com/article/S1...
565 citizens had been evacuated
30.8% (7.7– 53.8%).
30 days after evacuation
Asymptomatic and Pre-symptomatic SARS-CoV-2 Infections in Residents of a Long-Term Care Skilled Nursing Facility - King County, Washington
https://www.ncbi.nlm.nih.gov/research...
CDC 76 residents
categorized as asymptomatic or symptomatic at the time of testing and for previous 14 days
23 (30%) residents, antigen positive and symptomatic
13 (57%) were asymptomatic
10 of these 13 previously asymptomatic residents developed symptoms within 7 days
Therefore 3 (4%) out of 76 truly asymptomatic
RT-PCR) values indicated large quantities of viral RNA in asymptomatic, pre-symptomatic, and symptomatic residents
Symptom based screening on a particular day could fail to detect half of positive cases
Iceland
https://www.nejm.org/doi/full/10.1056...
Population screening, 57% symptomatic, 43% asymptomatic
CDC, Interim Clinical Guidance for Management of Patients with Confirmed Coronavirus Disease (COVID-19)
https://www.cdc.gov/coronavirus/2019-...
13% of positive children asymptomatic
Risk of transmission is thought to be greatest when patients are symptomatic since viral shedding is greatest at the time of symptom onset and declines over the course of several days to weeks.
WHO
81% of infections show mild symptoms
14% exhibit severe symptoms
5% fall critically ill
Asymptomatic coronavirus infection: MERS-CoV and SARS-CoV-2 (COVID-19)
https://www.sciencedirect.com/science...
The extent of asymptomatic MERS-CoV (2012) cases is about 9.8%
How much is covid-19 spreading via asymptomatic versus symptomatic infections? (4th May)
https://www.cebm.net/covid-19/covid-1...
Mathematical models SEIIR
Susceptible
Exposed
Infected, symptomatic
Infected, asymptomatic
Recovered
Therefore, need widespread antibody testing and contact tracing as soon as possible.
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