New Delhi (NVI): Coronavirus has majorly appeared as a respiratory virus, primarily affecting the periphery of lungs, and any theory of it infecting the blood vessels and circulating through the body is virtually unheard of.

However, in April, when the deadly pandemic was at its peak in most of the countries in the world, blood clots emerged as one of the many mysterious symptoms attributed to Covid-19. The disease had initially been thought to largely affect the lungs in the form of pneumonia.

Next followed the reports of young people dying due to coronavirus-related strokes, and then it was ‘Covid toes’- red, sore and sometimes itchy swellings on toes.

What all of these symptoms had in common was an impairment of blood circulation in the body. According to a report, 40 per cent of Covid deaths are related to cardiovascular complications.

“All these Covid-associated complications were a mystery. We see blood clotting, we see kidney damage, we see inflammation of the heart, we see stroke, we see encephalitis (swelling of the brain),” William Li, MD, president of the Angiogenesis Foundation was quoted as saying by Elemental.

“A whole myriad of seemingly unconnected phenomena that you do not normally see with SARS or H1N1 or, frankly, most infectious diseases,” he told the publication.

Mandeep Mehra, MD, medical director of the Brigham and Women’s Hospital Heart and Vascular Center says, “If you start to put all of the data together that’s emerging, it turns out that this virus is probably a vasculotropic virus, meaning that it affects the blood vessels.”

Mehra and a team of scientists discovered that the SARS-CoV-2 virus can infect the endothelial cells that line the inside of blood vessels. The findings were published in a paper in April in the scientific journal The Lancet.

The function of endothelial cells is to protect the cardiovascular system and release proteins that influence everything from blood clotting to the immune response. In the paper, the scientists showed damage to endothelial cells in the lungs, heart, kidneys, liver, and intestines in people with Covid-19.

According to Mehra, a growing body of evidence suggests that Covid-19 is not a respiratory illness alone. “This is a respiratory illness to start with, but it is actually a vascular illness that kills people through its involvement of the vasculature,” he told Elemental.

As per the latest research, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) enters the body through ACE2 receptors present on the surface of cells that line the respiratory tract in the nose and throat. Once in the lungs, the virus appears to move from the alveoli, the air sacs in the lung, into the blood vessels, which are also rich in ACE2 receptors.

Further explaining, Mehra says, “The virus enters the lung, it destroys the lung tissue, and people start coughing. The destruction of the lung tissue breaks open some blood vessels.”

“Then it starts to infect endothelial cell after endothelial cell, creates a local immune response, and inflames the endothelium,” he says.

On the other hand, influenza viruses like H1N1 are not known to do this, and the original SARS virus, a sister coronavirus to the current infection, did not spread past the lung. Other types of viruses, such as Ebola or Dengue, can damage endothelial cells, but they are very different from viruses that typically infect the lungs.