"In these outbreaks, aerosol transmission, particularly in these indoor locations where there are crowded and inadequately ventilated spaces where infected persons spend long periods of time with others, can not be ruled out", it had suggested.
Butler said there was no external political pressure behind the change in this instance. But the agency continues to believe larger and heavier droplets that come from coughing or sneezing are the primary means of transmission, Butler said.
The CDC also added that if you have pending COVID-19 test results, you should self-quarantine/isolate at home and "stay separated from household members". Aerosol particles are smaller and can linger in the air, moving with air currents from which they can be inhaled. In response to growing pressure, World Health Organization officials revised their guidelines slightly July 9, granting that some outbreaks may have been caused by aerosols, but saying that airborne transmission had not been definitively demonstrated.
Despite several studies that have shown the novel coronavirus can spread through small particles in the air, the CDC page now says that COVID-19 is thought to spread mainly between people in close contact - about 1.8 metres - and "through respiratory droplets produced when an infected person coughs, sneezes or talks".
Now, that update is nowhere to be found, prompting even more questions about the Trump administration's politicization of USA health organisations and information about the coronavirus.
The CDC had changed its language on asymptomatic transmission.
"I think that the science behind what turned out to be a draft statement is strong and agrees with my understanding of the data", Milton said. "To rectify the latest challenge, the CDC must acknowledge that growing scientific evidence indicates the importance of airborne transmission through aerosols, making mask wearing even more critical as we head into the hard fall and winter season".
On Friday, the agency reversed its new guidance on testing, published in August, that suggested people who have possibly been exposed to the coronavirus don't necessarily need to get tested for infection.
Jose-Luis Jimenez, a University of Colorado Boulder physicist and aerosol scientist, said Monday that he was surprised to see that the draft CDC guidance described the coronavirus as an "airborne virus".
Eric Feigl-Ding, an epidemiologist and senior fellow at the Federation of American Scientists, accused the Trump HHS of "muzzling" the CDC.