By Stephanie Stahl

PHILADELPHIA (CBS) — Headaches and sore throats are being added to an expanding list of possible COVID-19 symptoms. It means more people could be infected and eligible for testing.

The Centers for Disease Control and Prevention has expanded its list of possible symptoms of the coronavirus. Officials say they’re learning this virus is unpredictable, with a growing list of symptoms and strange side effects.

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“Literally every day we’re learning more, learning what it can do to the body,” Dr. David Agus said.

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New symptoms include: chills, repeated shaking with chills, muscle pain, headache, sore throat and loss of taste or smell.

The initial symptoms were fever, cough, shortness of breath and difficulty breathing.

“I think that we’ll have somewhat expanded criteria for what constitutes symptoms. I don’t think we want to test everybody who has a headache,” said Philadelphia Health Commissioner Dr. Thomas Farley.

The expanded list of symptoms means more people could be eligible for testing, but Farley says limited supplies remain an issue.

“I don’t think it’s gonna make a huge difference. What’s gonna make the biggest difference as far of the number people we test is how many swabs we have and how many tests our laboratories can run,” Farley said.

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For people with positive cases, some are developing widespread blood clots.

Most patients with serious cases of COVID-19 have lung damage but now doctors are seeing blood clots in places like the brain and kidneys.

“That is an absolutely new frontier. We don’t even know what will be the other atypical and unusual presentation of COVID-19,” cardiologist Dr. Samin Sharma said.

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It’s unknown whether the coronavirus itself causes blood clots or an inflammatory response.

“We’re seeing it in 30, 40, 50-year-olds — many times people that are not that symptomatic with the virus,” Agus said.

Blood thinners, the standard treatment for blood clots, don’t appear to work as well with COVID-19 patients. Doctors don’t know why.

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They say a variety of experimental treatments for COVID-19 have been disappointing.

Stephanie Stahl