Some patients with Covid-19, the disease caused by the new coronavirus, have mild symptoms and experience quick, full recoveries, while others face an extended path to recovery and can experience long-lasting health effects. In short, the virus looks different on everyone, experts say.

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There are some common symptoms that most people with Covid-19 experience, such as fever and a dry cough, but no symptoms are universal—and the severity of symptoms vary from person to person, Rosny Daniel, an ED doctor at the University of California-San Francisco who has recovered from Covid-19, told NPR's "Shots." For example, Daniel said patients who start feeling better after just a few days could see their symptoms return. He noted that, at first, he experienced aches and chills but quickly started to feel better. Then, seven days after Daniel contracted the disease, his symptoms returned and he started having trouble breathing, Daniel said.

In comparison, Darren Klugman, a pediatric cardiologist who also has recovered from Covid-19, told "Shots" that he initially developed "intermittent chills and body aches" as well as a low fever and a "very prominent cough." Ten days after his symptoms began, Klugman was "feeling [as if his] energy level was near normal," though his cough persisted a little longer, he said.

Fiona Lowenstein, a producer and yoga teacher who has recovered from Covid-19, wrote in the New York Times that she has seen a number of people have different experiences with the disease. Lowenstein wrote that she experienced gastrointestinal problems, a loss of smell, and "intense sinus pressure." Later, she developed fatigue, headaches, a sore throat, problems with focusing, and short-term memory loss.

Meanwhile, Charlie, a 24-year-old who is in a support group with Lowenstein, said he had a "relatively mild" case of Covid-19, though he was still experiencing fever, coughing, and shortness of breath 23 days into the disease.

Overall, Kenneth Lyn-Kew, an associate professor of pulmonology and critical care medicine at National Jewish Health, told Kaiser Health News that the majority of people with Covid-19 will experience a mild case of the disease and recover in "a couple of weeks," while some may have no symptoms at all. Those with a moderate case of Covid-19 likely will spend a few days in the hospital, often because they need oxygen support or because they have high fevers or a diarrheal illness that requires IV fluids.

Those with a severe case of Covid-19 experience acute respiratory distress syndrome and typically need to be placed on a ventilator, Lyn-Kew said.

When is a patient 'recovered' from Covid-19—and no longer contagious?

Because patients' symptoms can vary so much, it's difficult to determine when they will recover from the disease. "It's incredibly confusing, and there is a big amount of unpredictability to it," Daniel told "Shots."

Also, it's not currently known exactly how long a person infected with the new coronavirus can transmit the virus to others, making it difficult to determine when it's safe for Covid-19 patients to leave isolation.

CDC guidelines suggest that a patient with Covid-19 is able to leave isolation once they are free of fever for 72 hours or they have tested negative for the new coronavirus from at least two separate samples taken at least 24 hours apart. However, Lowenstein writes that it can be difficult for patients to receive follow-up tests. "My discharge instructions told me I'd need to be retested before I could be determined noncontagious. But, when I reached out to the Department of Health as instructed, I was told I couldn't be tested," she writes. "Instead, I was told to wait seven days from the first day of symptoms and to make sure the last three days were fever-free."

According to Ben Cowling, a professor of public health at the University of Hong Kong, that guidance is in line with experts' general understanding of other infections. "A rough guide for other infections is that infectiousness drops when the fever subsides," Cowling told "Shots."

But Aaron Carroll, a pediatrician and a professor at Indiana University School of Medicine, told NPR that some health care providers are uneasy with CDC's guidelines. "I will tell you that I think a lot of people I know are uncomfortable with that guidance," he said, adding, "They think that it may not be as conservative as it needs to be."

It's also unclear whether a person who contracts the new coronavirus develops an immunity that can protect them from becoming infected in the future.

As such, Daniel said he takes precautions to hopefully prevent himself from becoming re-infected. "I hope that my antibodies are all ramped up and I'm protected from getting sick again, but I don't know that for sure," he said. "So I'm treating it as if I don't have immunity, and I wear full protection at all times, by our hospital's guidelines, to make sure I'm still protecting myself" (Aubrey, "Shots," NPR, 4/13; Lowenstein, New York Times, 4/13; Graham, Kaiser Health News, 4/9).