A senior Trump administration official told Efe news in a statement that between May 11-17, nearly 1,800 travellers entered the country from Brazil and that each week more than 1,500 passengers arrive at USA airports on flights from Brazilian territory.
The White House on Sunday announced travel restrictions on Brazil, the nation with the second-highest number of COVID-19 cases.
Brazil has struggled to contain the virus, with President Jair Bolsonaro downplaying the disease as a "little flu" in the early stages of the outbreak.
President Donald Trump had said last week that he was considering limiting travel from Brazil.
The White House says it is prohibiting foreigners from travelling to the United States if they have been in Brazil in the past two weeks.
Earlier Sunday, Robert O'Brien, the USA national security adviser, had said an announcement was likely. "I don't want people to come here and infect our people".
The White House press secretary, Kayleigh McEnany, while speaking on the development noted that non-Americans who has been in Brazil in the last 14-days while seeking a visa to the USA would not be allowed to come to America.
"Because of the situation in Brazil, we're going to take every step necessary to protect the American people", O'Brien added.
O'Brien said the United States will look at restrictions for other countries in the Southern Hemisphere on a country-by-country basis.
"We didn't know at the time but we later learned that the Chinese continued to allow people to travel from Wuhan to Europe", he said.
The White House said Sunday it plans to donate 1,000 ventilators to Brazil. I hope we don't have a problem, "Trump said at the White House".
Coronavirus has yet to peak in Sao Paulo, Brazil's largest and worst-infected city, but the health care system is already beginning to break down.
It does not apply to United States citizens, legal permanent residents, or their family members.
Mr Bolsonaro again flouted social distancing protocols on Sunday, shaking hands and holding a child while not wearing a mask at a gathering of hundreds of supporters in Brasilia.