Briefing

What we know about long COVID

Understanding the symptoms, treatments, and causes of this mysterious illness

COVID-19 infections are on the rise again in America, prompting renewed concerns about so-called "long COVID." Here's everything you need to know about the condition, its causes, and its treatments:

What is long COVID?

"Long COVID" refers to long-term health problems that linger after a coronavirus infection, including fatigue, headache, brain fog, and digestive problems, among other symptoms per the Centers for Disease Control and Prevention. The unvaccinated, those who contract a serious bout of the virus, and those with underlying health conditions are believed to be at increased risk of developing these "post-COVID conditions," as the CDC refers to them, but anyone who contracts the virus is susceptible. 

Long COVID also does not affect everyone the same way, often complicating diagnosis. Further, it's not yet clear how much of a difference the vaccine makes: A large U.S. study published in May indicated coronavirus inoculation only slightly protects against long COVID, while a meta-analysis from early December estimated that at least one dose of the vaccine is almost 30 percent effective against the condition. 

What causes long COVID?

No one is 100% sure. For instance, some experts think an intense immune response during a primary COVID-19 infection may lead to inflammation and damage throughout the body, eventually resulting in long COVID, while some believe that the immune system just never really returns to normal after a patient recovers. Others point to possible virus-inflicted damage to the brain or the vagus nerve, which could explain symptoms like cognitive decline and gastrointestinal problems, respectively.

And then, among other theories, there are those researching the microscopic blood clot theory, which suggests long COVID symptoms are caused by post-infection microclots that block various blood vessels and disrupt the flow of oxygen throughout the body.

How is it diagnosed?

Given the condition's wide array of symptoms, doctors must rely on patient descriptions — and a process of elimination — to diagnose long COVID, the Times says. But some researchers are working to identify biomarkers that correspond to certain post-COVID conditions, like inflammation.

How long does it last?

Symptoms are typically first identified about four weeks after an initial infection and can then last weeks or even months, in some instances coming and going. 

But a new large study has found that, for most mild infections, long COVID symptoms often resolve after one year. Researchers for the study, which was published Jan. 11 in the journal The BMJ, analyzed almost 2 million records from a health maintenance organization in Israel, comparing the roughly 300,000 patients who tested positive for COVID and were not hospitalized to those who tested negative for the virus, Stat News summarizes. What they found was that, though patients with a mild case of COVID complained of varying long COVID symptoms in the year following their initial infection, those problems were often cleared up by year's end. The study also suggested that vaccinated individuals are at lower risk of developing breathing problems following a breakthrough infection than unvaccinated individuals; for other symptoms, the risk between the two demographics remains similar.

"The general message that symptoms improve over time is encouraging, but it may take a year or so for some symptoms to resolve," said Peter Openshaw, an experimental medical professor uninvolved with the research. "The study adds to the evidence that outcomes are improved by vaccination, even if vaccines don't prevent viral transmission very well."

Regarding flaws in their findings, researchers acknowledged that their results are from one country and might therefore prove difficult to graft onto others, and that the study "does not contradict evidence that a small number of patients do suffer from long-lasting symptoms," per Stat News.

Is there a cure for long COVID? 

Not at the moment. But there are certain steps long-haulers can take to hopefully ease and treat their symptoms. Make sure to talk to your primary care doctor; if you're concerned that what you're feeling is COVID-related, there is no need to wait. Otherwise, you might check out a post-COVID clinic, a number of which are cropping up nationwide and offer multidisciplinary and individualized care, both the Times and The Washington Post report. Be warned, however: Accessing a clinic might mean out-of-state travel, and can also prove difficult depending on your insurance. If you're medically eligible and also dealing with a bout of the virus, you might even try the COVID antiviral Paxlovid — a large study published in November found that those who ingested the drug within days of being infected appeared less likely to encounter long COVID months later. The study was not peer-reviewed, though, and it suggests Paxlovid could lessen the risk of long COVID in older adults or those with certain health problems, not necessarily in younger, healthier individuals. 

Experts have indicated that "rehabilitation through low-paced gradual increases in activity is key to recovery," in addition to symptom-specific treatment, the Post writes. But overall, experts advise remembering that healing isn't linear and will take time.

How common is long COVID?

A large CDC study from May 2022 found that one in five previously-infected adults under the age of 65 has experienced at least one symptom that could be considered long COVID. In those older than 65, that breakdown increases to one in four. And, "in an indication of how seriously the [agency] views the problem of long COVID," writes the Times, the authors of the study recommended "routine assess­ment for post-COVID conditions among persons who survive COVID-19."

For both age groups — above and below 65 years old — COVID patients' risk of developing respiratory symptoms and lung problems doubled compared to uninfected individuals, the study found. Regardless of age, the most commonly reported post-COVID infection symptoms were respiratory issues and musculoskeletal pain.

Long COVID "is real, definable, and causes significant patient suffering," Bruce Levy of the Brigham and Women's Hospital in Boston told the Post in February 2022. "The majority of people who got acutely infected felt totally normal before they had their infection, and now they don't feel normal. That's jarring."

Update Jan. 12, 2023: This article has been updated throughout to include new findings about long-term symptoms.

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