What Researchers Know So Far

What Researchers Know So Far
What Researchers Know So Far

Key Takeaways

  • Viruses other than COVID-19, like influenza, may cause lingering symptoms weeks after the fact, new research has found.
  • These could cause “long colds” that last as long as COVID symptoms.
  • Experts say it’s too early to compare the two conditions or the long-term impacts they may have.

New research has found that COVID-19 may not be the only respiratory virus that results in lingering symptoms. A study conducted by researchers at Queen Mary University of London and published in The Lancet’s eClinical Medicine suggests that some non-COVID viruses may cause “long colds” similar to long COVID.

The fact that other infections can cause lingering symptoms—collectively called “post-infection syndromes”—is not new, Giulia Vivaldi, statistician and PhD candidate at Queen Mary University and first author of the new report, told Verywell. “Post-infection syndromes that cause ongoing symptoms after infection crop up in history,” Vivaldi said.

“After the Spanish flu pandemic of 1918, for example, you get hints of people struggling with ongoing problems after these infections.” Until now, however, researchers haven’t known much about the topic. “They’re historically understudied and poorly understood,” Vivaldi said.

However, the COVID-19 pandemic brought a renewed focus to post-infection syndromes, Neha Vyas, MD, a family medicine doctor at Cleveland Clinic, told Verywell. “Long COVID has put the spotlight on [this aspect] of respiratory illnesses,” she explained.

Long-Term Cold vs. COVID Symptoms May Differ

The new research relied on data from COVIDENCE UK, a population-based observational study launched in May 2020.

Vivaldi and her team analyzed data from 10,171 people who had previously tested positive for COVID-19 and 472 who had a non-COVID acute respiratory infection. The other infection could have been pneumonia, bronchitis, influenza, tonsillitis, pharyngitis, the common cold, an ear infection, or a different upper or lower respiratory infection. Most of the participants were white and female.

The data was collected via questionnaires from January 21 to February 15, 2021, and none of the participants were vaccinated against COVID-19. People who had previously been infected with COVID-19 or a different respiratory illness within the four weeks leading up to the survey were excluded from the study so the researchers could focus solely on long-term effects.

The participants were asked whether they were still experiencing many different symptoms at least four weeks after their illnesses, including:

  • Coughing
  • Problems with sleep
  • memory problems
  • Difficulty concentrating
  • Muscle or joint pain
  • Problems with the sense of smell or taste
  • Diarrhea
  • Abdominal (stomach) pains
  • voice changes
  • Hair loss
  • Unusual heart racing
  • Lightheadedness or dizziness
  • Unusual sweating

They found that some people in both groups—those who had COVID-19 and those who had a different infection—experienced symptoms up to 12 weeks after their illness began.

People with a history of COVID-19 were more likely to experience problems with taste or smell and lightheadedness or dizziness. Those with a long cold were more likely to experience prolonged coughing, stomach pain, and diarrhea.

Vivaldi said she didn’t expect the participants to experience so many different symptoms. “The number of symptoms they were presenting with is what surprised us most,” she said. However, the study authors wrote that they saw “little difference” between the two groups.

She added that they still don’t know how prevalent long colds are, how long the symptoms of long colds generally last, or who is more likely to get a long cold. “People have asked, ‘What is a long cold?’ and they’re almost expecting a formal definition,” she explained. “We just don’t have that yet.”

It’s Too Early to Compare Long Colds vs. Long COVID

The new study was limited in a few key ways, Thomas Russo, MD, an infectious diseases expert at the University of Buffalo Jacobs School of Medicine and Biomedical Sciences, told Verywell. For starters, he said, some participants in the non-COVID group probably had COVID.

“If you had a negative home test, they lumped you in with the non-COVID group, but we know that test is imperfect,” Russo explained. Home tests are thought to detect COVID-19 80% of the time when a person is infected; PCR tests, on the other hand, are believed to detect COVID-19 95% of the time. “I suspect the non-COVID group was polluted by a lot of COVID,” Russo said.

It’s also worth noting the different sample sizes of people who had COVID-19 versus other respiratory illnesses, Vyas said. “This study was extremely skewed toward COVID, so you can’t make a whole lot of conclusions based on this study alone,” she said.

The demographics also make it difficult to generalize the findings, Vyas added: The participants were “mostly white, mostly female, mostly over 50, and that’s a very skewed population,” she said. “So you really have to take this study with a grain of salt.”

Thomas Russo, MD

I don’t think we want to equate [long colds] and long COVID. What we’re seeing with COVID has really been unique. We’ve had coronaviruses around forever, but we didn’t have [treatment] clinics popping up like we do now.

—Thomas Russo, MD

Russo said that while we don’t have enough data on long colds to talk about how prevalent or severe they usually are, we do know how debilitating and frequent long COVID-19 is. “We’ve been studying COVID very hard, and the seriousness of long COVID is a whole different order of magnitude,” he said.

Research suggests that, among people infected with COVID-19, up to 20% of 18 to 64-year-olds and 25% of adults 65 and older develop long COVID. Severe illness from COVID-19 and some underlying health conditions, including diabetes, asthma, and autoimmune diseases, increase the likelihood of long COVID. Being unvaccinated can also increase your risk.

Preventing Long-Term Symptoms and Complications

Staying up-to-date on all vaccinations and wearing a mask in crowded public areas when case counts rise are the best ways to avoid respiratory viruses and, therefore, long-term complications from them, Russo said.

If you notice lingering symptoms of any infection, it’s worth speaking to a healthcare provider, Vyas said. “If you’re miserable and it’s keeping you up at night, by all means, talk to your doctor,” she said. “You don’t have to grin and bear it.”

A healthcare provider can recommend treatments for your specific symptoms. “It really is dependent on the person, so I can’t generalize, but we’ve used over-the-counter [medications]nasal steroids, inhalers, oral steroids—many different things.”

What This Means For You

COVID-19 isn’t the only infection that can cause lingering symptoms ranging from annoying to debilitating. If you’re still experiencing symptoms weeks after an illness, experts recommend speaking with a healthcare provider about how to proceed. They may recommend over-the-counter or prescription medications that can make you more comfortable as you heal.

The article is in Portuguese



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