It said that if a person came in contact with someone infected with the virus that causes COVID-19 "you do not necessarily need a test" if you don't exhibit any symptoms, but that local public health officials or health care providers might still recommend one.
"Some medical procedures can produce very small droplets [called aerosolised droplet nuclei or aerosols] that are able to stay suspended in the air for longer periods of time", the World Health Organization website says.
"In general, indoor environments without good ventilation increase this risk", it read. It restricted the spread of respiratory droplets "when an infected person coughs, sneezes or talks".
The NYT also reported that scientists at the CDC strenuously objected to the new guidelines but were told by senior staff in an email obtained by the NYT that: "We do not have the ability to make substantial edits".
Previously, CDC suggested maintaining "good social distance" of about 6 feet, washing hands, routinely cleaning and disinfecting surfaces and covering your mouth and nose with a mask when around others.
According to the guidance, the CDC website states that in addition to using a mask, washing hands and staying "at least six feet away" from others, people should stay home and isolate themselves when they are sick and " use air purifiers to reduce airborne germs.
"Airborne viruses, including COVID-19, are among the most contagious and easily spread", the CDC said. "People who have COVID-19 can still spread the virus before they show symptoms (presymptomatic spread) or if they don't develop symptoms (asymptomatic spread)".
On Thursday, the NYT reported that the CDC was not only forced to accept the changed guidelines but that the changes were made without going through the CDC's standard scientific review process.
The revised guidance notes that the virus can additionally be spread by means of "small particles, such as those in aerosols" that linger in the air, and that breathing and singing can also lead to transmission.
"Current guidance from many global and national organizations focuses on hand washing, maintaining social distance and water droplet precautions", the scientists wrote in a letter published in the journal Medical Infectious Diseases.
After the letter is published, The WHO released a statement Describes how the corona virus can travel from one person to another, through the air during certain medical procedures, including air in congested indoor spaces.
Donald Milton, a professor of environmental health who studies how viruses spread and one of the 239 scientists that wrote the letter, said the CDC's update was a major improvement and that he was encourage to see the health institute paying attention.