The CDC posted new guidance on its website warning people about airborne spread.
A pandemic of the novel coronavirus has now killed more than 1 million people worldwide.
Over 35.3 million people across the globe have been diagnosed with COVID-19, the disease caused by the new respiratory virus, according to data compiled by the Center for Systems Science and Engineering at Johns Hopkins University. The criteria for diagnosis -- through clinical means or a lab test -- has varied from country-to-country. Still, the actual numbers are believed to be much higher due to testing shortages, many unreported cases and suspicions that some national governments are hiding or downplaying the scope of their outbreaks.
Since the first cases were detected in China in December, the virus has rapidly spread to every continent except Antarctica.
The United States is the worst-affected country, with more than 7.4 million diagnosed cases and at least 210,013 deaths.
California has the most cases of any U.S. state, with more than 833,000 people diagnosed, according to Johns Hopkins data. California is followed by Texas and Florida, with over 791,000 cases and over 717,000 cases, respectively.
More than 190 vaccine candidates for COVID-19 are being tracked by the World Health Organization, at least seven of which are in crucial phase three trials.
The U.S. death toll from COVID-19 has now surpassed 210,000, according to data compiled by the Center for Systems Science and Engineering at Johns Hopkins University.
The death toll reached 200,000 on Sept. 22 and continues to climb as several locations around the country see rises in cases.
The U.S. leads the world in COVID-19 deaths, followed by Brazil, which has over 146,000 and counting, and India, which has over 102,000 and counting.
After a back and forth last month, the U.S. Centers for Disease Control posted new guidance Monday on its website once again warning people about airborne spread of the coronavirus.
The updated guidelines state some infections can be spread by exposure to the virus in small droplets and particles that can linger in the air for minutes to hours.
The CDC added that those transmissions can take place, "within enclosed spaces that had inadequate ventilation. Sometimes the infected person was breathing heavily, for example while singing or exercising."
"Today’s update acknowledges the existence of some published reports showing limited, uncommon circumstances where people with COVID-19 infected others who were more than 6 feet away or shortly after the COVID-19-positive person left an area," the agency said in a statement.
The updated language does not change CDC recommendations on social distancing, mask wearing, avoiding large gatherings, and conducting any event or gathering outside as much as possible.
The new guidance came a month after the agency was criticized for posting guidance on airborne transmission on its site and then removing it two days later.
John Brooks, the chief medical officer for CDC’s COVID-19 response, apologized for the changes during a Sept. 21 briefing and told reporters that the initial posting went up too early since they were still conducting a scientific review.
-ABC News' Stephanie Epps
All New York City public schools located in the nine ZIP codes that have been deemed hot spots for rising COVID-19 cases will be closed, New York Gov. Andrew Cuomo announced on Monday.
The nine zip codes, located in Brooklyn and Queens, have seen a recent rise in positive tests -- about 100 public schools will be affected.
Mayor Bill de Blasio sent a proposal on Sunday to the state government requesting the closure of all schools and nonessential businesses in those ZIP codes. Cuomo approved the proposal on Monday.
The schools will be closed beginning Tuesday.
There were 12,594 new cases of COVID-19 and 19 fatalities confirmed in the United Kingdom over the past 24 hours.
The latest daily tally is just short of the records set over the weekend when Public Health England said 15,841 cases between Sept. 25 and Oct. 2 were not included in the United Kingdom's reported daily case counts due to a technical issue. The unreported cases were added retroactively to reach Saturday's count of 12,872 new case and Sunday's 22,961.
The cumulative total is now at 515,571 cases with 42,369 deaths, according to the latest data from the U.K. government.
ABC News' Joseph Simonetti and Christine Theodorou contributed to this report.
