A version of this story appeared in the September 21 edition of CNN’s Coronavirus: Fact vs. Fiction newsletter. Sign up here to receive the need-to-know headlines every weekday.

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“Airborne viruses, including COVID-19, are among the most contagious and easily spread,” the US Centers for Disease Control and Prevention (CDC) says in an updated guidance page on its website.

Scientists have noted the likelihood of the transmission of coronavirus through viral particles in the air for months, pushing health agencies to acknowledge it. The CDC changed its advice on Friday.

It now says the virus can commonly spread “through respiratory droplets or small particles, such as those in aerosols,” which are produced even when a person breathes. Previously, the CDC said that Covid-19 was thought to spread mainly between people in close contact – about 6 feet – and “through respiratory droplets produced when an infected person coughs, sneezes or talks.”

The CDC also added measures based on protecting yourself and others. It now says people should “stay at least 6 feet away from others, whenever possible,” and continues to direct people to wear a mask and routinely clean and disinfect. However, it also now says people should stay home and isolate when sick, and “use air purifiers to help reduce airborne germs in indoor spaces.”

The new guidance comes as the US fast approaches 200,000 deaths, and most of the country is headed in the wrong direction in terms of case numbers. In 31 states, the number of new Covid-19 cases has increased by at least 10% this past week compared to the previous week, according to data Sunday from Johns Hopkins University.

YOU ASKED. WE ANSWERED

Q: How can I tell if I have coronavirus or the flu (or both)?

A: Both the flu and Covid-19 can give you a fever, cough, shortness of breath, fatigue, sore throat, body aches and a runny or stuffy nose, the CDC said.

“Some people may have vomiting and diarrhea, though this is more common in children than adults,” it added.

But unlike the flu, Covid-19 can cause a loss of taste or smell.

And about half of coronavirus transmissions happen before any symptoms show up. (Many of those people spreading the virus silently are pre-symptomatic and are more contagious before they start showing symptoms.)

So the best way to know if you have the novel coronavirus or the flu (or both) is to get tested. The CDC has created a test that will check for both viruses, to be used at CDC-supported public health labs.

Send your questions here. Are you a health care worker fighting Covid-19? Message us on WhatsApp about the challenges you’re facing: +1 347-322-0415.

WHAT’S IMPORTANT TODAY

Police stop and question drivers at a checkpoint in Albury, Australia, on July 8.

Could Australia’s lockdown be a model for the US?

The Australian state of Victoria recorded just 11 new coronavirus cases Sunday, down from over 670 daily infections last month. Victoria’s experience shows once again that targeted lockdowns are effective in containing the virus: driving down infections, relieving pressure on health systems and creating space for contact tracing and mass testing. Elsewhere, however, strategies have been less successful, with partial closures bringing with them the misery of a full lockdown while not actually containing infections. James Griffiths reports.

Boris Johnson can’t wake up from his Covid-19 nightmare

The number of coronavirus cases in the UK is doubling roughly every seven days, according to the country’s chief scientific advisor, Patrick Vallance. If that rate continues to grow unabated, “by mid-October you would end up with something like 50,000 per day,” which “could lead to 200 deaths a day” by November, Vallance warned at a Monday press briefing.

The comments have fueled speculation that the government is preparing the ground for a second national lockdown, or other hard measures, in order to get cases back to a sustainable level.

Welcome to a week of high-level “digital diplomacy”

This week is the United Nations General Assembly – normally the Super Bowl of international diplomacy. But the pandemic means the UN’s 75th anniversary assembly will be a very different sight. Instead of mingling in the corridors of UN HQ in New York, the leaders’ faces will beam into the hall from thousands of miles away through hundreds of pre-recorded remarks. “The COVID-19 pandemic is a crisis unlike any in our lifetimes, and so this year’s General Assembly session will be unlike any other, too,” said UN Secretary-General Antonio Guterres at a news conference.

ON OUR RADAR

TODAY’S TOP TIP

Got a stress headache? This routine brings relief

As Covid-19 intensified, so did levels of stress and depression, according to a new study published in the Science Advances journal. If stress causes you a headache, try this quick workout to relieve the pain.

TODAY’S PODCAST

“Before you run off to the movies or your favorite restaurant, you do need to think carefully about how to balance the risks and the benefits, and what precautions you can take to try and keep safe.” – CNN’s Chief Medical Correspondent Dr. Sanjay Gupta

As some states move forward with reopening, many people are still uncertain about the safest way to eat out at a restaurant, go to the movies, or hit the gym. CNN’s Dr. Sanjay Gupta answers your questions and offers guidance for how public health measures can help keep us safe. Listen Now.