Test stored blood samples for COVID-19 antibodies
Blood samples that were taken in Italy during the period September 2019 to March 2020 have been tested for COVID-19 antibodies, with as many as 10% of patients testing positive for COVID-19 in spite of those samples pre-dating widespread infection in the area. Some of the samples that tested positive dated back to earlier than the first reported case of COVID-19 worldwide. These findings have been predominantly interpreted to indicate that COVID-19 began circulating far sooner than previously thought, but it is also possible that the positive tests instead are the result of antibodies to a different pathogen with sufficient overlap to result in positive tests. This possibility could be tested by simply testing even older blood samples. Such samples could be sourced from long-term research projects such as the Framingham Heart Study, or alternately even from anti-doping agencies such as WADA, which retains athletes' blood samples for later re-testing.
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