The pathogen has already done a fair bit of damage. It has only been five days since the patient began exhibiting typical COVID-19 symptoms, but already, menacing shadows can be seen in the CT scans of the lungs.

„It’s like frosted glass,” is how Christian Strassburg, a professor of internal medicine at the Bonn University Hospital, describes the changes made visible by the scan. „The lung tissue is saturated with fluid.” Secretions and dead cells are gumming up the walls of the pulmonary alveoli „like Jell-O,” he says.

„It is extremely difficult for oxygen to permeate a layer like that to get from the lung into the bloodstream,” the professor explains. It is a phenomenon he has been seeing frequently in recent weeks and it is caused by the novel coronavirus, SARS-CoV-2. The number of confirmed COVID-19 patients worldwide is now well over 4.2 million and the number of deaths is approaching 300,000. Meanwhile, doctors and biologists are doing all they can to gain a better understanding of the pathogen behind the pandemic.

SARS-CoV-2 behaves differently than almost any other virus that humans have faced before, and even now, several months into the pandemic, there is disagreement as to what percent of COVID-19 patients experience severe symptoms. Estimates tend to come in at around 5 percent of all infections. And in those cases, the virus unfolds unfathomable destructive power.

The epicenter of such infections is almost always the lungs. But as medical professionals now realize, the virus can also affect other organs and tissues – including the heart, the brain, the kidneys and the bowels. In the worst case, the body begins attacking itself. When the immune system spins out of control like that, doctors call it a „cytokine storm,” and when patients die as a result, multiple organ failure tends to be the cause.

Over 100 vaccine candidates are currently being developed worldwide to combat SARS-CoV-2, but in the worst-case scenario, it could take years before a vaccine is available. Until it is, the virus will still be with us. Even if the pandemic does weaken a bit, experts believe a second wave is just around the corner.

Early talk of COVID-19 as being mostly a mild illness has been proven to be „dangerously false,” Richard Horton, editor-in-chief of the medical journal The Lancet, has written. At the bedside, he says, it is „a story of terrible suffering, distress and utter bewilderment.” U.S. cardiologist Harlan Krumholz described the ferocity of COVID-19 in the magazine Science as „breathtaking and humbling.” The disease, he continued, „can attack almost anything in the body with devastating consequences.”

The best way to learn more about SARS-CoV-2 is to start small. Coronaviruses are a mere 160 nanometers in size. In order to multiply, the tiny pathogens are reliant on the cells belonging to a different organism.

The novel coronavirus likely comes from bat viruses, and it is thought that, even before it made the jump to humans, it developed the mechanism allowing it to bind with human cells. Some bat viruses are able to bind to a receptor called ACE2. This molecule can be found on the surface of human cells and helps regulate blood pressure. But it also functions as a kind of doorway to the interstices of the cell, and viruses that have the key can get inside.

Researchers believe that bats carry around 3,200 different coronaviruses. Chance, time and opportunity fueled the creations of the SARS-CoV-2 virus, which ultimately managed to jump to humans.

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