Articles

If you’re unfortunate enough to catch COVID-19, symptoms can linger long after the initial infection ⁽¹⁾. The same is true if you catch the flu ⁽¹⁾.

A recent study ⁽²⁾ found that some people who contract either COVID-19 or the flu still experience various symptoms three to six months after their infection. These symptoms include abnormal breathing, fatigue, pain, and anxiety ⁽²⁾.

What is long flu?

The study looked at the medical records of more than 270,000 COVID-19 patients and just under 115,000 flu patients ⁽¹⁾⁽²⁾. It discovered that around 42% of the COVID-19 patients and 30% of the flu patients experienced at least one symptom between three and six months after their infection ⁽¹⁾. Of the flu patients ⁽²⁾:

• more than 14% experienced anxiety or depression
• around 5% experienced abnormal breathing
• just under 4% experienced fatigue
• 5% experienced headaches
• just under 7% experienced abdominal symptoms and
• just under 2% experienced cognitive problems (‘brain fog’ ⁽³⁾).

The presence of lingering symptoms has led some to suggest the existence of so-called ‘long flu’ ⁽³⁾ – the flu equivalent of ‘long COVID’. The World Health Organization defines long COVID ⁽⁴⁾, or ‘Post COVID-19 condition’ ⁽⁵⁾, as a condition that usually occurs three months from the onset of COVID-19 and with symptoms that last for at least two months.

However, more research is needed to confirm the existence of long flu ⁽³⁾.

Long-flu versus complications of the flu

In addition to the possibility of long flu, the flu comes with a wide range of severity of illness ⁽⁶⁾. While the flu is just an unpleasant illness with minor symptoms for most people, the flu can be very serious for some.

The most common complications of the flu are bronchitis and pneumonia due to bacterial infections on top of the infection with the flu virus ⁽⁶⁾. Possible rarer, more severe complications include encephalitis (inflammation of the brain) and generalised whole-body infections ⁽⁶⁾. These often require hospital treatment ⁽⁶⁾. These more severe illnesses are more common in the elderly, the very young and people with chronic medical conditions, such as diabetes or heart disease ⁽⁶⁾.

A 2017 study followed the progress of 56 patients hospitalised with the flu. It specifically looked at their progress during the two years after their discharge from the hospital ⁽⁷⁾. The study discovered that some patients had long-term psychological difficulties and lung issues ⁽⁷⁾. More than half of patients were still experiencing difficulties at their two-year follow-up ⁽⁷⁾.

Annual vaccination is the most effective way to protect yourself against the flu and serious complications, especially if you’re in one of the high-risk groups ⁽⁸⁾.

Sources
(1) https://www.forbes.com/sites/roberthart/2021/09/29/long-flu-also-exists-but-is-less-common-than-long-covid-study-suggests/
(2) https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1003773
(3) https://www.sciencefocus.com/news/long-flu/
(4) https://www.who.int/publications/i/item/WHO-2019-nCoV-Post_COVID-19_condition-Clinical_case_definition-2021.1
(5) https://www.who.int/news/item/12-08-2021-post-covid-19-condition-who-supports-standardization-of-clinical-data-collection-and-reporting
(6) https://www.ecdc.europa.eu/en/seasonal-influenza/facts/questions-and-answers-seasonal-influenza
(7) https://www.nature.com/articles/s41598-017-17497-6
(8) https://www.who.int/news-room/feature-stories/detail/five-simple-steps-to-protect-against-flu