Public health experts initially advised people that the three most common symptoms of Covid-19 were fever, dry cough, and shortness of breath, but researchers and providers are finding that Covid-19 can manifest in various ways and cause many different symptoms. Here's a breakdown of reported symptoms so far.

Covid-19 guidance from clinicians at the forefront

The 3 'standard' symptoms of Covid-19—and why they were an initial focus

When the new coronavirus first began spreading, physicians around the globe reported that they were seeing three standard symptoms among a large number of Covid-19 patients: fever, dry cough, and shortness of breath.

A systematic review of medical literature performed by Charitini Stavropoulou, an associate professor in health services research at City, University of London, in March found that fever was reported among 82% to 87% of patients with mild to moderate cases of Covid-19.

David Aronoff, chief of the Division of Infectious Diseases at Vanderbilt University Medical Center, told NPR's "Goats and Soda" that the severity of fever can vary between cases. However, he said, "I think if someone has a fever, regardless of how long it's lasting, unless they can clearly attribute it to something else, that's a very reasonable symptom to seek an evaluation for" Covid-19.

Meanwhile, coughing "appears … two out of three times for patients with Covid-19," Stavropoulou told NPR. Aronoff explained that, given the effects Covid-19 can have on a patient's lungs, dry cough is a "very, very common symptom of the pneumonia that the [new coronavirus] can cause."

When it comes to shortness of breath, Stavropoulou's review found that the symptom occurred in fewer than 8% of milder cases but occurred more frequently in severe cases of the disease. Stavropoulou's review stated that some studies found shortness of breath "was a marker of severe" cases of Covid-19.

CDC recognizes 6 additional symptoms of Covid-19

But as the number of reported cases of Covid-19 increased globally, so did the number of reported symptoms associated with the disease. Based on new reports and research, CDC last month officially recognized six additional Covid-19 symptoms: chills, muscle pain, headache, sore throat, loss of smell, and loss of taste.

Aronoff explained that patients often experience chills and shaking before a fever. Meanwhile, a report published by the World Health Organization (WHO) in February noted that almost 15% of nearly 56,000 Covid-19 patients in China had experienced muscle pain.

Claire Steves, a geriatrician and senior lecturer at King's College London, told NPR that research also shows headache is "an important" early symptom of Covid-19 that often occurs alongside other standard symptoms of the disease.

Like muscle aches, headaches can be a symptom of a wide range of ailments, but Aronoff said patients should consider a headache to be a sign of Covid-19 if the symptom "is sticking around a bit longer than they are used to" or is associated with other symptoms associated with the disease.

Aronoff also told NPR that a sore throat is a "minor symptom" seen in Covid-19 patients. Data published by WHO in March showed that fewer than 14% of Covid-19 patients experienced a sore throat.

In comparison, Carol Yan, an otolaryngologist and head and neck surgeon at UC San Diego Health, told NPR that loss of smell or taste have become strong indicators of Covid-19. Research conducted by Yan found that about 70% of Covid-19 patients included in the study reported a loss of smell or taste.

As such, Yan said if a patient is experiencing those symptoms, she "would tell them that they should consider self-quarantining themselves and contacting their health care providers."

Emerging symptoms of Covid-19

Providers and researchers in recent weeks have continued reporting new findings on and additional symptoms of Covid-19 as they learn more about the disease.

Specifically, while researchers and physicians originally focused on how the novel coronavirus affects the lungs, experts and clinicians are now realizing the virus is capable of attacking multiple parts of the body and causing various symptoms and complications ranging from stroke and hallucinations to rashes and a rare inflammatory syndrome.

In one example, clinicians around the world have reported that some Covid-19 patients experience cardiac symptoms such as myocarditis and irregular heart rhythms that sometimes lead to cardiac arrest—even in patients with no underlying heart conditions. Kidney damage also is becoming a commonly reported issue among Covid-19 patients, as well as blood clots that can travel from patients' veins to their lungs, brains, and other organs.

Some emerging symptoms of the disease are disproportionately impacting younger patients. For instance, doctors in recent weeks have reported a rising number of cases of a deadly inflammatory syndrome that afflicts children within days or weeks after they become infected with the new coronavirus.

Meanwhile, dermatologists are increasingly reporting cases of so-called "Covid toes," which manifests as redness, burning, itching, and/or swelling in the toes of patient with Covid-19. Doctors say the condition resembles chilblains, which is an inflammatory reaction usually seen on the extremities of people who spent too much time in cold or damp weather. In some cases, the Associated Press reports that Covid toes may be the first or only symptom of Covid-19 patients with the disease experience.

Doctors are reporting other skin-related symptoms among Covid-19 patients, as well. According to AP, in one study of 88 patients at an Italian hospital, one out of five patients experienced skin symptoms, the most common of which was a rash on the patient's midsection.

So far, an international Dermatology Covid-19 Registry has received more than 400 reports of skin manifestations from dermatologists in 21 countries, NPR reports.

Doctors also are reporting a growing number of Covid-19 patients with symptoms of neurological damage, including confusion and hallucinations, as well as gastrointestinal symptoms.

"Older and frailer and more co-morbid people tend to be getting this cluster of abdominal symptoms and delirium symptoms and headache as well," Steves told NPR.

Reports of emerging symptoms indicate new coronavirus becomes a 'global disturbance' to the body

As providers and researchers continue to uncover new symptoms tied to Covid-19, they are recognizing that the novel coronavirus is more complicated than other respiratory viruses they have seen.

Geoffrey Barnes, an assistant professor at the University of Michigan, said there's still a lot that experts don't know about the new coronavirus, which "literally did not exist in humans six months ago." He said, "We had to rapidly learn how this virus impacts the human body and identify ways to treat it literally in a time-scale of weeks."

Mandeep Mehra, a professor of medicine at Harvard Medical School, said the increasing reports of new symptoms tied to the virus shows in severe cases it can cause widespread disruption in the body—which ultimately can lead to death. "What this virus does is it starts as a viral infection and becomes a more global disturbance to the immune system and blood vessels—and what kills is exactly that."

Still, public health experts note that the majority of people who become infected with the new coronavirus experience only mild cases of Covid-19.

Esther Freeman from Massachusetts General Hospital said while there still is more researchers and providers can learn about the new coronavirus and Covid-19, "[t]he public health message is not to panic" (Neergaard, Associated Press, 5/17; Bernstein/Cha, Washington Post, 5/10; Godoy, "Goats and Soda," NPR, 5/6).