The progress against the virus, however, is threatened by several new variants, experts said, adding that face masks and social distancing measures were still very much needed.
About 4% of cases in the country are related to a more contagious variant first detected in the United Kingdom, according to Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention.
"We have projections that it may be the dominant strain by the end of March," she told CBS's "Face the Nation" on Sunday.
The country logged more than 639,000 new COVID-19 cases in the week ended Feb. 14, according to a Reuters analysis of state and county reports. Compared to the previous week, new cases increased in only three out of 50 states: Alaska, Nebraska and South Dakota.
(Open https://tmsnrt.rs/2WTOZDR in an external browser to see a state-by-state graphic.)
Deaths fell for a second week in a row, down 1.8% last week to 21,787. Excluding a backlog of deaths reported by Ohio, fatalities were down 15% last week. Cumulatively, nearly 486,000 people have died from the virus in the United States, or one in every 673 residents.
The average number of COVID-19 patients in U.S. hospitals fell to 74,000 last week, the lowest since mid-November, according to a Reuters analysis of data from the volunteer-run COVID Tracking Project.
Nationally, 5.7% of COVID-19 tests came back positive for the virus, the lowest level since the week ended Oct. 25, according to data from the COVID Tracking Project.
