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Since the COVID-19 pandemic began, many people have compared the novel coronavirus to the flu. That makes sense, considering that flu is so familiar to most of us. The problem, however, is that such comparisons have led some people to minimize the severity of COVID-19 by dismissing it as “just like the flu.” Translation: We deal with some version of this every year, and it’s not that big a deal.

But the past year has proven that COVID-19 is, in fact, a very big deal. According to the World Health Organization (WHO), nearly 3 million people worldwide have died from COVID-19 as of April 2021. In contrast, the WHO estimates that about 290,000 to 650,000 people worldwide die from the flu each year (which is not insignificant but considerably smaller than the number of COVID-19 deaths over the past year).

While many people who contract either the flu or COVID-19 develop only mild symptoms, at the moment it seems clear that COVID is more apt to lead to serious — including sometimes fatal — complications.

What’s more, a new study suggests that COVID-19 tends to be more dangerous than the flu specifically for people who have an underlying autoimmune condition.

The study, which was published in the journal Rheumatology, includes data on 133,589 autoimmune disease patients who contracted COVID-19 in the U.S., Spain, or South Korea between January and June 2020. Of that group, 48,418 people had to be hospitalized. The researchers compared this subgroup to 70,660 autoimmune disease patients who had been hospitalized with influenza between 2017 and 2018.

The most common autoimmune diseases among patients were psoriasis (PsA), rheumatoid arthritis (RA), and vasculitis.

According to their findings, “those admitted with admitted with COVID-19 had more respiratory complications including pneumonia and acute respiratory distress syndrome, and higher 30-day mortality” compared to those who were hospitalized with the flu, the authors wrote.


  • 15 to 43% of patients admitted with COVID-19 had acute respiratory distress syndrome, compared to 17 to 29% percent of patients admitted with the flu.
  • 13 to 53% of patients admitted with COVID-19 had pneumonia, compared to 19 to 36% percent of patients admitted with the flu.
  • 6 to 25% percent of patients admitted with COVID-19 had a higher mortality rate, compared to 2 to 4% percent of patients admitted with the flu.

While it’s not clear exactly why COVID patients were more likely to face more respiratory complications and death, inflammation in the blood vessels likely plays an important role. Both the flu and COVID are usually described as “respiratory” viruses, but COVID often causes vascular damage as well.

“Our study showed that up to 8 percent of hospitalized patients with COVID-19 and prevalent autoimmune diseases suffered VTE [venous thromboembolism, a type of dangerous blood clot] and the incidence of VTE is higher in hospitalized COVID-19 patients versus influenza patients in most of the databases. There are extensive evidence demonstrating increased risk of thromboembolism among patients with autoimmune disease,” the authors noted.

In comparison to COVID patients with autoimmune disease who were able to recover at home, those who were sick enough to require hospitalization were more likely to be female, older, and have hypertension, chronic kidney disease, or heart disease.

“Compared to influenza, COVID-19 is a more severe disease, leading to more complications and higher mortality,” the researchers concluded. “Future studies should investigate predictors of poor outcomes in COVID-19 patients with autoimmune diseases.”

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Global Influenza Programme. World Health Organization. https://www.who.int/teams/global-influenza-programme/surveillance-and-monitoring/burden-of-disease.

Tan EH, et al. COVID-19 in patients with autoimmune diseases: characteristics and outcomes in a multinational network of cohorts across three countries. Rheumatology. March 16, 2021. doi: https://doi.org/10.1093/rheumatology/keab250.

WHO Coronavirus (COVID-19) Dashboard. World Health Organization. https://covid19.who.int.

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