Fever, cough, shortness of breath.
Those are the three symptoms prominently listed on the Centers for Disease Control and Prevention's website under coronavirus symptoms.
But as case counts continue to rise in the United States and across the world, it's clear that COVID-19, the disease caused by the virus, causes a much wider range of symptoms. The more detailed descriptions of the illness that are emerging show how doctors and researchers are still learning about the disease, which was first reported just three months ago, in real time.
COVID-19 can begin in similar ways among patients, regardless of a person's age or health status.
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Medical student warns young people about seriousness of coronavirusApril 1, 202002:37
Very often, extreme fatigue hits first.
Hedy Bauman, 74, was so weak she could barely make it home from a short walk to the store. Reading a few pages of the newspaper was exhausting.
"My bathroom is maybe 15 steps from my bed," Bauman, of Silver Spring, Maryland, told NBC News. "I wasn't sure I could get from the bathroom to my bed." She developed chills, but no fever.
Bauman's doctor said her symptoms were consistent with what physicians are learning about other coronavirus cases, though they are still waiting for the results from Bauman's COVID-19 test.
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Brendan McLaughlin, 28, felt lightheaded and weak before the fever, chills and body aches began.
McLaughlin went to the emergency room at Holy Name Medical Center in Teaneck, New Jersey, where he works as a security guard, thinking maybe he had the flu.
That test was negative, but a test for the coronavirus was positive. McLaughlin said he'd never felt so sick in his life.
"I'd been healthy," McLaughlin said. "I try to eat right. I take care of myself."
One of the first major reports on coronavirus symptoms was published by the World Health Organization in February, following their mission to China. That report, based on nearly 56,000 cases there, found the most common symptoms were fever (88 percent) and dry cough (68 percent). Nearly 40 percent of those patients experienced fatigue. Shortness of breath, stomach issues and weakness were less common.
Since that report, other symptoms related to COVID-19 have emerged.
Many patients who've either tested positive for the coronavirus, or have been told by their physicians to assume they have it, also develop a headache and sore throat. Others become sick to their stomach with nausea or diarrhea.
Some patients say they have no interest in eating. Many report they're losing their senses of taste and smell, the British Rhinological Society said recently.
Just this week, a small study published in JAMA Ophthalmology added another potential COVID-19 warning sign: pink eye, also known as conjunctivitis. A third of the 38 patients in the report had the inflammatory eye condition.
But it's also becoming more clear that some infected people spreading the virus don't have any symptoms at all.
Contagious before symptoms
Dr. Robert Redfield, director of the CDC, told NPR this week that as many as a quarter of patients are asymptomatic. And a report published by the CDC Wednesday found evidence that infected people can spread the virus before they develop symptoms, although it seems to be rare.
The phenomenon is called "presymptomatic transmission," which is also a known way that the flu spreads.
The CDC report was based on 243 coronavirus cases in Singapore. Researchers there carefully traced all of individuals that patients had been in contact with before becoming ill.
They ultimately determined 6.4 percent of transmissions in the study were from presymptomatic patients.