COVID-19, influenza attack heart in different ways, study says

Healthcare experts warn about a possible fall and winter surge of COVID-19 to go along with the yearly influenza surge.

That’s just one the ways SARS-CoV-2 and influenza have been linked. COVID-19 and influenza both present as respiratory illnesses. Also, an individual can get both at the same time, which can make things even more complicated, especially from a diagnostic standpoint.

In fact, symptoms of the two resemble each other so much that it’s created a “COVID is just like the flu” mantra among some in the public and media, despite the Centers for Disease Control and Prevention pointing out that COVID-19 and influenza go their separate ways at certain points. There are differences.

In fact, there may be profound differences, as a recent study in Immunology points out. John Fraser, Ph.D., one of the study’s co-authors from the University of Queensland, Australia, said in a press release that “the two viruses appear to affect cardiac tissue very differently, which we want to get a better understanding of in larger cohort studies. What we have categorically shown is that COVID is not ‘just like the flu.’”

Researchers found that the damage in the DNA in the hearts of patients who’ve died from COVID-19 does not at all resemble the way influenza works. 

Arutha Kulasinghe, Ph,D., the study’s corresponding author, told Fierce Healthcare that “it makes sense to compare COVID to flu, specifically the 2009 influenza virus, because this is the last known pandemic. Both viruses cause respiratory illnesses, and, in our study, we sought to identify the changes, if any, between how severe COVID compared to severe influenza. Our study, whilst small, shows clear differences between the two viruses.”

The researchers studied the hearts of seven individuals who died from COVID-19 from Brazil along with the hearts of two people who died from flu and six patients who died from other causes. They examined the DNA of the samples using transcriptomic profiling. The invasiveness of obtaining heart biopsy samples limited previous studies of the effects of COVID-19 to a review of blood biomarkers and physiological measurement.

Aside from noting the difference between how influenza and SARS-CoV-2 attacks the heart, the study could perhaps lead to a better understanding of long COVID, Kulasinghe tells Fierce Healthcare. “What surprised us was that we were expecting very similar molecular differences in COVID and flu—which is not what we found. The DNA damage signature (fingerprint) was in stark contrast to that of flu. In fact, the inflammatory signals were all suppressed in COVID. We are not sure what this means clinically at this stage and need to do a lot more work. I think what it is showing us is that there are clear biological differences between COVID and flu and this might help obtain biomarkers associated with a long COVID phenotype.”

The cardiac samples from the influenza patients showed that the flu caused excess inflammation of the heart. That wasn’t the case with the heart samples of the individuals who died from COVID-19. Fraser said in the press release that “COVID-19 attacked the heart’s DNA—probably directly and not just as a knock-on from inflammation.”

The study states that “pandemic H1N1 influenza drives a cytokine storm of generalized inflammation disrupting the heart which presents with fever, tachycardia, and arrhythmias. In contrast, COVID-19 drives a now recognized syndrome which can result in acute myocardial infarction, myocardial injury, heart failure, disseminated thrombosis, hypotension, arrhythmias and sudden cardiac death.”

And even though SARS-CoV-2 can attack multiple organs, COVID-19 is not like HIV, either, Kulasinghe tells Fierce Healthcare. “HIV is quite different in mode of action, spread and complications. I would hesitate to compare this to COVID.”

Not all experts are convinced.

A study in January 2021 in the International Journal of Medical Sciences is titled “Similarities and Differences Between HIV and SARS-CoV2.” In that study, Spanish researchers conclude that “although at first sight these viruses do not resemble each other, the molecular mechanisms used are common: the increased of pro-inflammatory cytokine synthesis, the modifications in intestinal microbiota, the NETs formation. Basic science has been trying to understand these mechanisms for years and the greater the knowledge, the lesser the damage to the population in this pandemic and in the future.”

The small study with a narrow focus on heart damage done by University of Queensland researchers might be a step toward determining what damage COVID-19 can do to other organs and bodily functions. Damaged DNA is linked to chronic diseases like neurodegenerative disorders, atherosclerosis, diabetes and cancer.

The study states that “further work is warranted to discern whether direct SARS-CoV-2 infection of cardiac tissue or other physiological events are responsible for the cardiac injury observed in our cohort.”