The coronavirus began quietly spreading in the U.S.

Robert Redfield, director of the CDC, said Friday during a call with reporters.

The CDC traced the early spread in several ways, including what's called syndromic surveillance of emergency department records, tests of respiratory specimens and analyses of the virus's genetic sequences from early cases.

Additionally, three separate COVID-19 cases in California confirmed "cryptic circulation of the virus by early February," the CDC authors wrote.

SARS-CoV-2 is the name of the coronavirus that causes the COVID-19 illness.

"The findings do show that in late February, early March, there were several importations of the virus from Europe to California and northeastern United States and possibly elsewhere," Redfield said.

Health officials announced the first coronavirus case in the U.S.

30 when the CDC announced the first evidence of person-to-person spread — a married couple in Chicago.

It is now clear the virus was indeed spreading, particularly during the month of February.

"Limited community spread of the virus that causes COVID-19 occurred before the two nontravel associated cases that were reported in late February," Redfield told reporters on Friday.

26, health officials in Santa Clara County, California, announced the virus had been spreading in the community: A woman diagnosed with COVID-19 had not traveled to China, and had no contact with the only other known cases in the region.