New research indicates the coronavirus could remain in the air for more than eight minutes after talking.
Human speech generates droplets that can carry virus and can linger for 8 to 14 minutes, according to a research by U.S. National Academy of Sciences.
This research put into question over U.S. President Donald Trump's decision to reopen schools.
Trump said earlier he "totally disagreed" with U.S. top infectious disease expert Dr. Anthony Fauci, who advised that the White House should be cautious with reopening schools.
"We're opening our economy. People want it open. The school are going to be open," said Trump on Wednesday.
Previously, Dr. Fauci said that given a lack of vaccination, schools should be closed during the fall even if some students may feel safe doing so, as classrooms are always filled with students and teachers talking.
As the number of confirmed COVID-19 cases in the U.S. tops 1.4 million, some U.S. states like California are planning to reopen their economies this month by allowing access to book stores and hair salons.
In Wisconsin, the state's Supreme Court has also reached a decision to declare its stay-at-home order invalid.
