In language posted Friday and now removed, CDC said Covid-19 most commonly spread between people who are in close contact with one another, and went on to say it's known to spread "through respiratory droplets or small particles, such as those in aerosols, produced when an infected person coughs, sneezes, sings, talks or breathes".
According to the CDC, these particles can be inhaled into the nose, mouth, airways, and lungs and cause infection.
The posting appeared to confirm emerging research that suggests tiny particles can transport the virus some distance, especially in indoor or poorly ventilated environments.
Explaining the spread between animals and people, the page said, "At this time, the risk of COVID-19 spreading from animals to people is considered to below".
"Most public health organisations, including the World Health Organisation, do not recognise airborne transmission except for aerosol-generating procedures performed in healthcare settings".
People who do not have symptoms and are not close contacts of an infected person still do not need a screening, unless it is recommended by a medical provider or public health official, according to the latest CDC statement.
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".
The warning came as the CDC recently added language to its website recognizing the possibility that the virus can spread through aerosols, small particles that can linger longer in the air than larger droplets, which the CDC had previously pointed to as the major suspect in transmission.
The reversal was lauded by the president of the Infectious Diseases Society of America, Thomas File, who on Friday said "the return to a science-based approach to testing guidance from the [CDC] is good news for public health and for our united fight against this pandemic". Spread from touching surfaces is not thought to be the main way the virus spreads, clarified CDC.
They also updated the guidance that particles can remain in the air longer and travel farther than originally thought.
"Evidence has been accumulating for some time".
The World Health Organization recognized the threat of aerosols in July, after hundreds of scientists urged the global body to address airborne spread.
In a decision that has left many public health experts confused and suspicious, the Centres for Disease Control and Prevention has abruptly changed its testing guidelines for covid-19. "And 6 feet apart may be insufficient, esp indoors w/ poor ventilation".
It also points out that the use of masks should not replace other prevention measures, but be complementary to them. "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".