FILE - A transmission electron microscope image shows SARS-CoV-2, also known as the 2019 novel coronavirus, which causes COVID-19, isolated from a patient in the United States.
Note the crown-like spikes on the outer edge of the virus, hence the term (NIAID-RML)RELATED: UK variant, South Africa variant, Brazil variant: A guide to known coronavirus mutationsAdvertisementIn the United States, a study found that 10% of Marine recruits who had evidence of prior infection and repeatedly tested negative before starting basic training were later infected again.
That work was done before the new variants began to spread, said one study leader, Dr. Stuart Sealfon of the Icahn School of Medicine at Mount Sinai in New York."Previous infection does.