For many people, what started out as a relatively mild case of COVID-19 persisted into a lingering condition that took weeks or months before their suffering subsided -- some have yet to fully recover. They live with long COVID, a condition health care providers have struggled to treat since the COVID-19 pandemic was declared in March 2020.
It's hard to put a number on what percentage of people have developed long COVID, since many mild cases of the virus go undetected and there's such a wide range of what "counts" as a long COVID symptom. But somewhere between 10% of people who tested positive for COVID-19 but didn't need to be hospitalized, and 50% to 70% of people who were hospitalized, developed some degree of long COVID, according to a major review of long COVID research published at the beginning of this year in Nature Reviews Microbiology.
Fortunately, rates of long COVID, also called "long-haul COVID" or "post-COVID conditions," seem to be declining compared to the pandemic period. According to a report from the US Centers for Disease Control and Prevention published this month, the prevalence of long COVID among American adults who reported having the virus went from about 19% in June 2022 compared to 11% this past June. The CDC notes that after declining, the rate is unchanged since early this year.
The condition can be mildly bothersome or debilitating, running the gamut of faintness, nausea and constipation, to organ damage or life-changing mental or cognitive symptoms. Nonspecific symptoms that can easily fall into the category of other health conditions, like breathlessness, chronic headaches and chest pain, can make accurately diagnosing long COVID feel like catching a shadow.
Despite what researchers are still trying to figure out, including more treatment options and better diagnostic tools, health care providers and scientists have made headway in their understanding of the condition. Here's a roundup of what we know now.
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What are the symptoms of long COVID?
After the initial infection is cleared, COVID-19 has been found to linger in about every system of the body among long COVID patients. Symptoms include heart or cardiovascular problems, respiratory issues, immune system effects, neurological symptoms and even some reproductive issues.
Dr. Nasia Safdar, medical director of infection control at the University of Wisconsin spoke with CNET in 2021, when scientists were first getting a grip on long COVID, that the key to discerning the condition is to pay attention to new symptoms that develop or ones that never go away -- about 30 days post-infection. This separates long COVID from the initial viral infection itself.
The World Health Organization offers a slightly more narrow definition of new or continuing symptoms three months out after the initial infection, lasting for at least two months.
- Difficulty thinking or concentrating ("brain fog").
- Difficulty breathing, shortness of breath or cough.
- Chest pains.
- Headache or migraines.
- Fast-beating or pounding heart.
- Joint or muscle pain.
- "Pins-and-needles" feeling.
- Nausea, diarrhea or other gastrointestinal problems.
- Sleep problems.
- Dizziness upon standing (lightheadedness).
- Mood changes, such as depression or anxiety.
- Change in sense of smell or taste.
- Reproductive system problems, including changes to the menstrual cycle and erectile dysfunction.
In 2021, Safdar said the most common symptoms she saw in her work with patients were symptoms that affected "higher executive functions."
"Concentration, memory, being able to do your job the way you could before," Safdar said. "Those kinds of symptoms are hard for people to describe, but they've clearly noticed a change from the way they were before."
In 2023, cognitive impairment and neurological symptoms are still relatively common for those who experience effects post-COVID-19. The authors of the Nature review called them a "major feature of long COVID," with a meta-analysis finding fatigue in 32% of people with COVID-19 after 12 weeks, and cognitive impairment in 22%.
One set of symptoms of COVID-19 that affected many people sick from earlier variants is the loss of their sense of taste, smell or both, which meddled with their memories and mental health in addition to disrupting their enjoyment of food. Fortunately, this has become a much less common symptom with newer versions of the virus, and the majority people who recovered from COVID-19.
The 'typical' long COVID patient
People ages 36 to 50 were most likely to be diagnosed with long COVID, according to a Fair Health study. The study, which looked at data from more than 78,000 patients from October 2021 through January 2022, also found more diagnoses in women than in men, and that about 30% of people had no prior diagnosis with a chronic health condition.
Other factors that may make a person more likely to develop long COVID is being unvaccinated and having underlying health conditions pre-COVID-19, including type 2 diabetes and a past bout with Epstein-Barr virus (the virus that causes mono), according to the Nature review.
People who need to be hospitalized after contracting COVID-19 are also more likely to develop long COVID. Socio-economic factors also may make someone more susceptible, as having a lower income and being unable to take off work to rest increases the risk of long COVID, per the review.
In short, there is no "typical" patient with long COVID, since people with more mild cases can and do develop the condition, as do children. In children, those who have attention deficit hyperactivity disorder, chronic urticaria and allergic rhinitis (allergic reactions including hives and seasonal allergies) may be more likely to develop long COVID, research shows.
The various conditions or factors that seem to increase someone's chances of developing long COVID highlight the complexity of the disorder, the different ways it interacts with the immune system and brain and its varying causes.
Causes of long COVID
The authors of the Nature review say that there are "likely multiple, potentially overlapping, causes of long COVID." Some of these mechanisms, they conclude, include viral persistence (the virus staying with the body's tissue), neuroinflammation, excessive blood clotting and autoimmunity or disruptions to immune response.
Dr. Devang Sanghavi, a critical care physician with the Mayo Clinic, told CNET in August 2022 that there are a few broad ways to consider the different causes of long COVID: People with severe enough afflictions that they developed organ or cell damage; people who were hospitalized and have lingering health effects from that hospitalization; and people who weren't hospitalized, but developed symptoms as a response to the virus. The last group, in particular, has been the focus of research into how some people's immune systems respond, or even over-respond, to the virus.
The different causes and mechanisms of lingering symptoms and health effects illustrate the complexity of COVID-19 and its ability as a respiratory virus to create lasting impacts on other parts of the body.
No long COVID 'test'
According to the CDC, there is no single test that can determine whether or not you have long COVID. Instead, a health care provider looks at your health history, including if, when and the likelihood you had COVID-19 (based on a positive test result, your symptoms or exposure history), and when symptoms of long COVID began.
This lack of any sort of definitive marker makes a long COVID diagnosis even more frustrating for people suffering. And while health care providers are more aware of its presence this year than earlier in the pandemic, blood work or other routine tests may turn up normal in patients with COVID-19, requiring them to do their own advocacy to get the treatment they need.
"One message that I would like to send out to these patients is that their symptoms are real," Sanghavi said of the difficulties of living with, diagnosing and treating long COVID.
"We may not have answers right now about why and how and what we can do to help them, but they should not be struggling and suffering alone," Sanghavi said.
Because long COVID symptoms are so broad, there is no blanket treatment. Instead, treatment for long-haul COVID will involve doctors working to address your specific symptoms. Various breathing exercises, physical therapy or medications may be prescribed, according to information from Johns Hopkins Medicine.
Trials on the effects of different drugs for treating long COVID, including anti-inflammatory and anticlotting medications and antihistamines, have also been started. However, according to a STAT report, the number of clinical trials researchers with the National Institutes of Health have conducted since getting money from Congress to research long COVID is "underwhelming."
There's also some early information to suggest that COVID-19 antiviral medications, such as Paxlovid, might reduce the risk of long COVID, as Nature reported in a March article, but more research is needed.
Because the symptoms of long COVID can overlap so evenly with symptoms of chronic fatigue syndrome, aka ME/CFS, another disabling and lasting health condition, strategies used for ME/CFS patients may also work for long COVID patients, according to Nature.
The American Academy of Physical Medicine and Rehabilitation, which represents medical experts who work with patients who are disabled or in chronic pain to help them function, has published guidance statements, including what physicians should look for when treating and screening neurological symptoms of long COVID.
Survivor Corps, an organization for people with long COVID, has a map of post-COVID care centers for patients who are looking for more resources or treatments. (As of this past spring, there's a message on the website that says it's not being updated anymore, so some information could be outdated.)
Preventing long COVID and the role of reinfection
Researchers know that having a severe case of COVID-19 can make it more likely for a person to experience long COVID, and that vaccines reduce that risk of severe disease. While research is ongoing, Johns Hopkins Medicine says "it is likely that being vaccinated reduces the risk" of long COVID.
But research on how vaccines impact the symptoms of people who already have long COVID is unclear. One smaller study found that a little more than 16% of people experienced a relief of long COVID symptoms post-vaccine, but about 21% actually experienced a worsening of their symptoms. Most didn't experience a change. A review published online by The Lancet also found mixed results on vaccines for long COVID symptoms.
Because COVID-19 is still around, reports of people getting reinfected with COVID-19 a second, third or even fourth time are becoming more common. The safest bet in reducing long COVID risk seems to be reducing your risk of getting COVID-19 again, and then minimizing your chance of having severe COVID-19 by staying up-to-date on your vaccines (there's an updated booster rolling out this fall) and getting treatment for COVID-19 in the first days of your symptoms if you're at higher risk of getting really sick.