Dear Dr. Roach:

We are learning a lot about short-term to long-term impacts from COVID-19, especially on the cardiovascular system. But we don’t hear about “long flu” or similar impacts. Is that because COVID really is different, or is it more the case that we have billions of people affected and an unprecedented amount of money and research going on around the world?

If we studied the flu or other respiratory viruses to the same degree, would we find similar impacts beyond the symptoms of the obviously ill? — B.D.

Answer: I think your question is very insightful, and the answer is that it is a combination of both.

Influenza infection (“the flu”) can lead to people getting persistent symptoms that can last for months after infection. This phenomenon is more common with COVID, and although we don’t really understand why it happens, some excellent work has recently been published.

Symptoms up to a month after a respiratory virus of any kind are common, but having persistent symptoms after three months is one common definition of post- COVID condition, sometimes called “long COVID.”

A study published last September addressed your question directly.

The authors looked at nine separate symptoms known to persist after COVID infection: anxiety or depression; chest or throat pain; abnormal breathing; muscle aches; fatigue; headache; abdominal symptoms; cognitive symptoms (such as “brain fog”); and pain.

All of these symptoms were present in both flu and COVID survivors, but every symptom was more common in COVID survivors compared with flu survivors.

Cardiovascular symptoms were still present in 15% of COVID survivors three months after infection, compared with 8% of those after flu infection. Anxiety and depression were the most common symptoms in both survivors — 20% of COVID survivors and 14% of flu survivors.

There’s one other factor to consider. Since long COVID has been reported, it may also be that people are more attuned to persistent symptoms than they were after other infections in the days before the pandemic.