Coronavirus symptoms — and what to do if you have them

The Reverend Wayne Gadie of Emmanuel Baptist Church in Malden gets a coronavirus test.Pat Greenhouse/Globe Staff

This story was last updated June 29. // See the latest information from the CDC here.

The novel coronavirus COVID-19 continues to spread and disrupt daily life in the United States and around the world, with over 10 million confirmed cases and 500,000 deaths worldwide as of June 29. What are the symptoms of COVID-19, and what should people do if they become ill? Here are some answers.

What are the symptoms of coronavirus?

According to the US Centers for Disease Control and Prevention, the initial symptoms are typical of other common illnesses: fever, cough, and shortness of breath. Since March, the CDC has also added difficulty breathing and more symptoms: new loss of sense of smell (anosmia), new loss of sense of taste (ageusia), chills, repeated shaking with chills, fatigue, muscle or body aches, headache, sore throat, congestion or runny nose, nausea or vomiting, and diarrhea.

The symptoms may appear two to 14 days after exposure to the coronavirus, according to the CDC.

The illness, known officially as COVID-19, can be mild to severe.

Older adults, 65 and older, and people who have severe underlying chronic medical conditions, like heart or lung disease or diabetes, are at a higher risk for getting very sick from the illness, the CDC says.

The CDC says other people who may be at risk are people with HIV, people with asthma, and pregnant women. Recent reports have also noted that younger people can become very ill.

What are the symptoms of coronavirus, and how is it treated?

The US Centers for Disease Control says little is known about the virus, but it still has some tentative answers.

How do you know it’s not just allergies?

Heading into summer, more people will be sniffling, red-eyed, blowing their noses, and sneezing due to seasonal allergies. But they won’t have fevers.

“What really distinguishes allergies from viral infections is the absence of fever,” says Dr. Daniel Kuritzkes, chief of the Division of Infectious Diseases at Brigham and Women’s Hospital. People who suffer from seasonal allergies typically know the difference, he noted.

How do I know it’s not just the cold or the flu?

Colds and the flu, which are both caused by viruses, are harder to differentiate from the coronavirus, Kuritzkes said.

A cold can bring on a sore throat, runny nose, fever, and nasal congestion, though it’s not usually associated — at least early on — with a phlegm-producing cough, he said.

The flu has a “pretty abrupt onset,” with a high fever, headaches, muscle aches, generally feeling terrible, and also possibly a cough. It’s not usually preceded by a sore throat and it may or may not involve nasal congestion, he said.

The bottom line: A severe cold, the flu, and a mild case of coronavirus “could be difficult to distinguish” from each other, Kuritzkes said.

What if you have symptoms?

If you think you have been exposed to COVID-19 and develop a fever and symptoms such as a cough or difficulty breathing, call your doctor for medical advice, the CDC advises.

The CDC offers a “self-checker” on its website to advise you if you might be sick.

The Massachusetts Department of Public Health says you can also call 211 to ask questions about prevention, symptoms, and treatment.

If you’re in a high-risk group, err on the side of caution and call early, even if your illness is mild, CDC says.

The CDC also says that if your symptoms escalate, you should get medical attention immediately. Emergency warning signs include but are not limited to difficulty breathing or shortness of breath, persistent pain or pressure in the chest, new confusion or inability to arouse, and bluish lips or face.

People should “stay vigilant” about whether they are developing fever or other symptoms, Kuritzkes said.

Jaclyn Reiss and Jeremiah Manion of the Globe staff contributed to this report.