Coronavirus was on 'low-level circulation' in US from December 2019, finds US-based study

Coronavirus was present in the United States as far back as in December 2019, weeks before the first-ever case was confirmed officially on January 21 by the Chinese government, a new antibody testing study by the National Institutes of Health (NIH) published Tuesday has found. Researchers at NIH identified a limited number of cases of SARS-CoV-2 infection in at least five US states—Illinois, Wisconsin, Pennsylvania, Mississippi, and Massachusetts, that broke out as early as January 7, 2020. 

NIH collected samples under the All of Us Research Program. The results also expanded on the findings from US Centers for Disease Control and Prevention (CDC) study that suggested SARS-CoV-2, the virus that causes COVID-19 had spread in the US two years ago and was circulating at low levels. This implies that the Americans were already infected with the novel coronavirus in December 2019 even before the disease was publicly declared spreading out of China’s Wuhan, the then epicenter of the virus outbreak. The breakthrough findings came to light after the researchers analysed more than 24,000 stored frozen blood samples contributed by program participants across all 50 states between January 2 and March 18, 2020. 

“This study allows us to uncover more information about the beginning of the U.S. epidemic and highlights the real-world value of longitudinal research in understanding dynamics of emerging diseases like COVID-19,” said Josh Denny, M.D., M.S., chief executive officer of All of Us and an author of the study. 

The NIH researchers detected antibodies against SARS-CoV-2 using two different serology tests that have emergency use authorization from the FDA in at least nine participants’ samples. These samples were all from outside the major urban hotspots of Seattle and New York City, the key points of entry of the virus in the US at the time. The positive samples came as early as January 7 from participants and were collected “prior” to the first reported cases in those states. "These included individuals with specimens collected January 7 from Illinois, January 8 from Massachusetts, February 3 from Wisconsin, February 15 from Pennsylvania, and March 6 in Mississippi,” the All of Us researchers said in the journal Clinical Infectious Diseases. 

Due to limited SARS-CoV-2 testing capacity in the US at the start of the epidemic (during January – March), testing was focused only on symptomatic patients. To minimize the possibility of false positives, researchers worked with Quest Diagnostics and followed CDC guidance to use sequential testing on two separate platforms,  Abbott Architect SARS-CoV-2 IgG ELISA and the EUROIMMUN SARS-CoV-2 ELISA (IgG). 

"Antibody testing of blood samples helps us better understand the spread of SARS-CoV-2 in the US in the early days of the US epidemic when testing was restricted," said lead author Keri Althoff, an associate professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health. “This study also demonstrates the importance of using multiple serology platforms, as recommended by the CDC.”

Low-level circulation of SARS-CoV-2 in 2019

As now the scientific community with more understanding of the coronavirus is aware that the antibodies take two weeks after infection to build in the recovered patients, the findings indicate that some of the participants were already infected in December. "Among the first 12 known cases of SARS-CoV-2 infection in the United States officially, the earliest recognized symptoms onset date was January 14, 2020, and all 12 cases had recently traveled to mainland China,” the researchers explained. But at the time the US federal government only recommended testing people with symptoms and now the NIH study “contributes to the evidence of low-level circulation of SARS-CoV-2 in many states in the US at the start of the epidemic,” the study purported. 

The study, however, does not focus on the overall origin of the coronavirus spread in the world, but that around the time, it may have transmitted across to the US. Scientists do not have evidence if the infected participants had travelled to China or had contracted the virus via community spread that had already started happening within the country.