What is 'long COVID'? Causes, symptoms, and risks may vary

Motorists line up to take COVID-19 tests.

June 28, 2021 2:41 PM PT

For untold numbers of people around the world, a bout with COVID-19 is just the beginning.

Those in this unlucky group may have thought they’d recovered from the disease. But weeks or months later, they find themselves contending with a baffling array of symptoms that don’t quite add up to COVID-19 and just won’t go away.

It’s a condition that has come to be known as “long COVID,” also known as post-acute sequelae of COVID, or PASC.

However, it remains steeped in mystery. Scientists can’t say for certain how many people ultimately suffer from the lingering symptoms, why exactly they occur or whether any particular population is more at risk.

But given that more than 33.4 million people nationwide — including almost 3.8 million Californians — have tested positive for the coronavirus at some point during the pandemic, and the true infection count is likely even higher, officials say it’s important for people to be aware of the possibility, as well as the warning signs.

One study in Italy found that more than half of COVID-19 patients ages 6 to 16 had at least one symptom of long COVID for more than four months, with many experiencing symptoms severe enough to impair their daily activities, said Dr. Christina Ghaly, the Los Angeles County health services director.

A study from the United Kingdom found that of teenagers infected with the coronavirus, 15% suffered from long COVID symptoms that interfered with their daily lives.

Dr. Rochelle Walensky, director of the U.S. Centers for Disease Control and Prevention, said last week that the agency “is continuing to work to identify how common these longer-term effects are, who is the most likely to get them and whether symptoms eventually resolve.”

Here’s a closer look at a condition that threatens to outlast the pandemic:

What is long COVID?

Long COVID is one name for a puzzling syndrome that can afflict people who are infected with the coronavirus.

The condition can last for weeks or months, and perhaps longer.

What are the symptoms?

Some symptoms are the same as regular COVID-19: fever, fatigue, headaches, coughs, difficulty breathing or shortness of breath, and loss of smell or taste.

Others are seemingly unique to long COVID, such as heart palpitations, depression, dizziness upon standing, joint or muscle pain, depression or anxiety, and difficulty concentrating or focusing, a condition sometimes called “brain fog.”

Patients suffering from long COVID say the symptoms can come and go without warning.

“For some people, they can be severely debilitating,” Walensky said during a briefing on Tuesday.

Who is most at risk of getting long COVID?

The CDC says long COVID can affect people who had only mild cases of COVID-19 and even those who were asymptomatic.

However, some experts think there is more convincing evidence that long COVID tends to occur after severe COVID-19 or symptomatic illness.

Well-done studies compare people — over the same period — with coronavirus infections with those who did not have infections. Those studies suggest “true long COVID symptoms are more common after symptomatic or severe disease,” said Dr. Monica Gandhi, a UC San Francisco infectious disease expert.

What causes long COVID?

One plausible explanation is that the body’s immune response to coronavirus infection generates “a massive inflammatory reaction you get to try to fight the virus,” Gandhi said.

Symptomatic or severe illness can produce the kind of “disorganized, innate, inflammatory response” that can lead to long COVID, Gandhi said.

Can vaccines prevent long COVID?

Long COVID is extremely unlikely to occur in someone who is fully vaccinated, Gandhi said.

If the body is exposed to the coronavirus after vaccination, the immune system — instead of producing a disorganized, inflammatory response — is primed to generate “a very organized response to the virus,” making long COVID unlikely, Gandhi said.

Post-vaccination, the immune system basically says, “‘OK, I’m going to adapt to fight this particular virus,’ comes in and saves the day,” Gandhi said. Such an organized response resolves symptoms quickly.

Ghaly agreed, saying, “If the virus can’t take hold in your body — if it can’t get into your system and if it can’t start replicating — then it doesn’t have a chance to get to the point where you might translate into having long-haul symptoms.”

“Whether your concern is serious illness or death from COVID, or your concern is long-haul symptoms from COVID, either way, the vaccine is the best way to protect yourself against either,” she said.

To date, more than 60% of Californians have received at least one vaccine dose, and 49% are considered fully vaccinated, according to the CDC.

Are there any risk factors for getting long COVID?

Women are more likely to contract long COVID than men, Gandhi said, although it’s unclear why.

And people who have preexisting conditions that make them more likely to suffer from severe COVID-19 — such as heart disease or lung disease — are more likely to get long COVID, Gandhi added.

Are vaccines a treatment for long COVID?

Not officially, but about one-third of those with long COVID have reported that their symptoms improved after receiving a dose of COVID-19 vaccine.

Akiko Iwasaki, an immunobiologist at Yale, is one of the principal investigators of the Yale COVID Recovery Study, which seeks to understand whether the vaccines are responsible for this improvement and, if so, why.

She has theorized that COVID-19 survivors still have coronavirus proteins and fragments of viral RNA lingering in their systems, causing an array of problems. If so, a dose of COVID-19 vaccine could be prompting the immune system to clear out the stragglers.

Can long COVID affect people who were in good health before they got COVID-19?

Yes.

Andy Slavitt, who served as a senior advisor to President Biden’s COVID-19 response team, said in May that one of his sons was still suffering from long-term problems half a year after he was infected with the coronavirus.

“He’s young and fit and in the prime of his life,” Slavitt said. “But six months later, he still suffers from tachycardia, shortness of breath and ongoing and frequent flu-like symptoms. His hands are cold to the touch. Neither he nor his parents — my wife and I — are sure how long this will last.

“Many young people are in this situation, and many, many have it worse,” Slavitt added.

Should doctors be on the lookout for post-COVID-19 symptoms in survivors?

Yes. Healthcare providers should be aware of the potential for post-COVID-19 illness, according to recent research published in the CDC’s Morbidity and Mortality Weekly Report.

The report said that among more than 3,000 adult patients who did not need to be hospitalized for their COVID-19 illness, almost 70% had to visit an outpatient facility one to six months after being diagnosed with a coronavirus infection.

Two out of 3 of them were diagnosed with something new, and “symptoms potentially related to COVID-19 were common new visit diagnoses,” the report said.

Generally, visits for these symptoms decreased after two months, the report said, but for some patients, they persisted for as long as six months.

“In other words, even patients who were not hospitalized for COVID-19 infection were commonly referred for additional evaluation for COVID-19-related symptoms and conditions after their initial illness,” Walensky said. “We have seen post-COVID conditions in people of all ages, and this makes it even more important, for anyone who is eligible, to get vaccinated.”