Study shows that COVID-19 was present in five U.S. states in December 2019, even before the first reported case in China

By Angela Betsaida B. Laguipo, BSNJun 21 2021Reviewed by Benedette Cuffari, M.Sc.

In a recent study published in Clinical Infectious Diseases, a group of researchers aimed to identify exactly how early the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was circulating throughout the United States. In their work, the researchers tested residual archived samples from routine blood donations collected by the American Red Cross.

Study: Serologic Testing of US Blood Donations to Identify Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2)–Reactive Antibodies: December 2019–January 2020. Image Credit: Diana Sklarova / Shutterstock.com

The SARS-CoV-2 spread

SARS-CoV-2, which is the virus behind the coronavirus disease 2019 (COVID-19), was first reported in Wuhan, China in December 2019. Since then, SARS-CoV-2 has continued to spread to 192 countries and regions around the world, infecting over 177 million people as of June 19, 2021.

The United States reported its first case of SARS-CoV-2 on January 21, 2020, in a 35-year-old American citizen traveling from Wuhan, China to his home in Washington state. This individual had a symptom-onset date of January 19, 2020. Importantly, two other individuals of the 12 cases that were first identified in the United States around this time identified their symptom-onset dates to be January 14, 2020.

It was not until much later in 2020 that researchers at the U.S. Centers for Disease Control and Prevention (CDC) discovered that people in several states in the U.S. were infected with SARS-CoV-2 much earlier than January 2020.

The study

The researchers aimed to determine if SARS-CoV-2 was present in the United States earlier than what was previously reported by identifying whether reactive antibodies were present in the blood samples that were collected before January 21, 2020. To this end, the team assessed residual archived samples from 7,389 routine blood donations collected by the American Red Cross between December 13, 2019, and January 17, 2020.

The samples were from donors in nine states including Connecticut, California, Iowa, Michigan, Massachusetts, Oregon, Rhoda Island, Wisconsin, and Washington. The team tested the samples for anti-SARS-CoV-2 antibodies.

Samples were first tested by pan-immunoglobulin (pan-Ig) enzyme-linked immunosorbent assay (ELISA) against the full spike protein. Those that were found to be reactive by this assay were subsequently tested by immunoglobulin G (IgG) and IgM ELISAs, a microneutralization test, Ortho total Ig S1 ELISA, and receptor-binding domain RBD)/angiotensin-converting enzyme 2 (ACE2) blocking activity assay.

Of the 7,389 blood samples that were tested, 106 were found to be reactive by the pan-Ig ELISA. Of these 106 reactive specimens, 90 samples were subjected to further tests. The researchers found that 84 of these 90 samples exhibited neutralizing activity. Further, one of these samples was found to exhibit S1 binding activity, whereas another was found to demonstrate RBD/ACE2 blocking activity of more than 50%, thereby suggesting the presence of reactive antibodies against SARS-CoV-2 in these samples.

“The findings of this report suggest that SARS-CoV-2 infections may have been present in the United States in December 2019, earlier than previously recognized.

The CDC is continuing to work with federal and nongovernmental partners to conduct ongoing surveillance using blood donations and clinical laboratory samples for SARS-CoV-2 infection in multiple sites across the United States.”

Notably, antibodies to SARS-CoV-2 were identified among donations from Iowa, Connecticut, Massachusetts, Wisconsin, and Rhode Island. This is important, as these samples were collected several months before SARS-CoV-2 was officially identified to be circulating in these states.

Shedding light on the dynamics of how SARS-CoV-2 spread from the earliest months of the COVID-19 pandemic will assist scientists who are looking to better understand the mechanisms by which this virus spreads. This information can also help organize, plan, and inform the allocation of resources and, at the same time, help prevent future outbreaks.