Oct. 5 (UPI) -- The U.S. Centers for Disease Control and Prevention posted a long-awaited update on the agency's COVID-19 website Monday clarifying that the disease can sometimes be spread through airborne transmission and can travel more than 6 feet in unventilated spaces.
The agency said evidence shows the coronavirus can spread from particles that linger in the air even after an infected person has left, like the way tuberculosis, measles, and chicken pox are spread.
"The virus that causes COVID-19 appears to spread more efficiently than influenza but not as efficiently as measles, which is among the most contagious viruses known to affect people," the website said. "People who are infected but do not show symptoms can also spread the virus to others."
The update said that under certain conditions, people with COVID-19 seem to have infected others who were more than 6 feet away in poorly ventilated spaces. Some cases appear to have been transmitted when an infected person was breathing heavily, for example while singing or exercising, the agency's updated website said.
The update is a re-stating of an unapproved draft that appeared earlier on the federal health agency's website and was then removed.
The agency said that so-called aerosol transmission was not the most common way to acquire the virus.
The easiest way to catch the highly contagious disease is to be in close contact (within 6 feet) of an infected person and inhale respiratory droplets when that person coughs, sneezes, sings, talks, or breathes, the agency said.
Wearing a cloth covering over the nose and mouth significantly reduces the spread of both respiratory droplets and airborne transmission, the agency said.
The agency recommended avoiding crowded indoor spaces and making sure that indoor spaces were properly ventilated to bring outdoor air in as much as possible.
"In general, being outdoors and in spaces with good ventilation reduces the risk of exposure to infectious respiratory droplets," the agency's website said Monday.
The CDCs update now aligns with research from the World Health Organization, which has said since July that research showed the virus was spread, in certain cases, by airborne transmission in nursing homes, restaurants, choirs and gymnasiums.