WASHINGTON, Dec. 10 (Xinhua) -- U.S. researchers have found antibodies against COVID-19 in blood samples dating back to mid-December 2019, weeks before the country's first officially-confirmed infections of the disease.

In a study conducted by scientists from the U.S. Centers for Disease Control and Prevention (CDC), residual archived samples from 7,389 routine blood donations collected by the American Red Cross from Dec. 13, 2019 to Jan. 17, 2020, from donors resident in nine states were tested at the CDC for anti-coronavirus antibodies.

Of the 7,389 samples collected from the states of California, Connecticut, Iowa, Massachusetts, Michigan, Oregon, Rhode Island, Washington, and Wisconsin, 106 were reactive by pan-immunoglobulin. Further confirmation testing of 90 samples suggests the presence of anti-SARS-CoV-2-reactive antibodies.

Specimens collected on Dec. 13-16, 2019, and those collected between Dec. 30, 2019 to Jan. 17, 2020, were summarized separately.

The results of the research were published late last month on the Clinical Infectious Diseases journal.