Science Vs Coronavirus: How Many Silent Spreaders Are There?
May 1, 2020
They dig into how many people who test positive never show symptoms and why follow-up tracking changes those estimates. Researchers describe universal testing on a cruise ship and a community antibody survey that found many symptom-free positives. The conversation covers hidden lung changes in some asymptomatic cases and what silent spreaders mean for testing and tracing.
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Passenger Who Didn’t Know He Was Infected
- Mark Jorgensen boarded the Diamond Princess cruise and initially dismissed coronavirus concerns but ended up quarantined when cases appeared onboard.
- He tested negative then later positive while remaining completely asymptomatic throughout his infection.
Antibody Tests Need Symptom Histories
- Antibody tests show prior exposure but cannot tell if someone had symptoms unless you ask them, so serology alone can't measure asymptomatic rates.
- Vivek Naranbhai's Chelsea study combined finger-prick antibody tests with symptom questionnaires to estimate asymptomatic proportion.
Preliminary Chelsea Study Found High Asymptomatic Share
- In Vivek Naranbhai's Chelsea sample 63 people had antibodies and about 40% of those reported no symptoms in the prior four weeks.
- This preliminary, small study contrasts with other studies, showing wide variability in asymptomatic estimates.