Even a mild case of COVID-19 can come with some pretty miserable symptoms, including debilitating headaches, extreme fatigue and body aches that make it feel impossible to get comfortable.

To make matters worse, it's becoming more and more apparent that a subset of people who've "recovered" from COVID-19 will go on to experience symptoms that linger well beyond testing negative for the virus. These individuals are sometimes referred to as "COVID long-haulers," and experts are searching for answers about this condition that's now being termed post-COVID syndrome.

"We're seeing continued evidence that a fair number of people who have had COVID-19 continue to feel the effects of this illness for weeks to months after recovering from the worst of their symptoms or complications," says Dr. Sandeep Lahoti, gastroenterologist at Houston Methodist. "We still don't understand how long these symptoms can truly persist, but we do know that many of these people would benefit from specialized care and, in some cases, regular follow up."

What are the symptoms of post-COVID syndrome?

Just as COVID-19 itself can come with a range of symptoms, so, too, can post-COVID syndrome.

The most common symptoms that can linger include:

• Fatigue
• Difficulty breathing
• Joint pain
• Chest pain
• Brain fog, including an inability to concentrate and impaired memory
• Loss of taste and/or smell
• Sleep issues
  
  

"We're not sure exactly how long these symptoms can persist, but we know that they can last at least six months or longer in some people," Dr. Lahoti says. "The manifestations of these symptoms are interesting and somewhat unique. For instance, MRI scans show myocarditis in some of these people, indicating that the heart muscle can remain inflamed several months out — even if heart-related symptoms weren't prevalent during their illness."

As for the cause and long-term consequences of these lingering symptoms? That's still unclear, too.

"We don't yet know why post-COVID syndrome occurs, but hypotheses range from hidden areas of infection to a prolonged inflammatory response," explains Dr. Lahoti. "We're also not sure what the long-term outcomes of these lingering symptoms might be, if any. We know this syndrome can certainly impact quality of life, but right now we don't expect any severe impacts, such as ongoing organ damage."

Can anyone experience lingering COVID-19 symptoms?

When it comes to the life-threatening cases of COVID-19, doctors expect people who were hospitalized for severe pneumonia or stroke to need specialized care and frequent follow-up after being discharged.

But, although not completely defined just yet, post-COVID syndrome isn't exclusive to people who experienced organ damage during their illness. It's also not exclusive to people whose symptoms warranted a trip to the emergency room.

"Post-COVID syndrome can be seen in people who went to the ER with concerning symptoms or who had advanced symptoms that required a brief hospital stay, but it can also occur in people who had mild symptoms and self-treated at home," warns Dr. Lahoti. "The important thing to note is that these are people who might not have required care from a specialist during their actual illness, but may now benefit from specialized care as these lingering symptoms continue to affect their daily lives."

The actual frequency of post-COVID syndrome is still largely up for debate, and different studies find this condition to be more or less common in various groups of people.

"Some studies show that only 10% of people with COVID will go on to develop post-COVID syndrome, while other studies are showing much higher percentages — some even suggest that up to 70% of people experience persistent symptoms," says Dr. Lahoti.

According to Dr. Lahoti, there are hints and suggestions as to who's most likely to develop lingering symptoms, though.

Those who seem to be most at risk of developing post-COVID syndrome include:

• Adults over the age of 50
• People who experienced a more severe case
• Individuals with underlying health conditions, particularly cardiopulmonary issues, hypertension, diabetes or obesity
  
  

What should someone who's experiencing post-COVID syndrome do?

For those who experienced only a mild illness and self-treated at home but are now dealing with post-COVID syndrome symptoms, Dr. Lahoti recommends scheduling an appointment with your primary care physician.

"Your doctor can diagnose the severity of your lingering symptoms, helping to treat the ones that are mild and referring you to a specialist for any that are more advanced," explains Dr. Lahoti.

If you were hospitalized for more severe symptoms during your illness, you may already have a cardiologist you can follow up with about any heart issues, such as chest pain, or a pulmonologist you can check in with to address any lung issues, such as difficulty breathing. Talk to your primary care doctor about whether you might benefit from being referred to one of these specialists if you don't already have one.