The country's first known case of the illness that fueled a pandemic and claimed hundreds of thousands of American lives was detected in a man who lived outside of Seattle, Washington.
The man, who was in his 30s, had reportedly traveled to Wuhan and came home two days before the Centers for Disease Control and Prevention began screening travelers.
At the time, health officials knew that the virus claimed six lives in China. With this new case, the U.S. became one of only five countries with reported coronavirus infections.
WATCH: Jan. 21, 2020 news coverage on the nation's first confirmed case of coronavirus
Dr. George Diaz, head of infectious diseases at Providence Medical Center, spoke to KOMO-TV this week about treating "patient one" at a time when little was known about the virus.
A photo taken at Providence in 2020 shows the patient inside an insolation pod that would prevent him from infecting doctors and other hospital staff. Diaz said that isolation was emotionally difficult for his patient.
"He became even more frightened about what was going to happen, as he'd seen reports in China where there were many deaths. He was very fearful that things could go poorly for him as well ... That is one of the hardest parts of taking care of COVID patients is the fear that they have that they are going to die," Diaz said.
He said he was one of the first doctors in the world to administer remdesivir for COVID-19 treatment. Five days after the treatment, the patient was discharged from the hospital. Diaz said that one year later, the two still keep in touch.
As of Thursday, the number of confirmed coronavirus cases neared 97 million worldwide and 24 million in the U.S., according to the Johns Hopkins University dashboard. More than 2 million have died globally, with over 406,000 American deaths.