COVID-19, the illness caused by the coronavirus, starts when someone is infected, likely by the virus being carried in droplets from an infected person’s cough, sneeze, or breath.

These droplets could be in the air or on a surface that you touch and then if you touch your eyes, nose, or mouth, you can be infected.

What makes this coronavirus so dangerous to humans is simply that it’s “novel,” meaning it’s new to humans. We don’t have any immunity to this virus - our bodies don’t have any way to fight it. It is also highly transmissible and easy to get like the common cold, but much more dangerous.

Once the virus enters your body, it infects healthy cells. There, it makes copies of itself and multiplies throughout your body. About 80 percent of the time, symptoms are mild, but 20 percent of the time, the immune system fights back and the lungs become inflamed. One expert described it as “millions of cells from the immune system invade the infected lung tissue and cause massive amounts of damage in the process of cleaning out the virus and any infected cells.”

Some patients develop acute respiratory distress syndrome or severe breathing difficulties that lead them to be put into a medically induced coma and intubated (have a breathing tube put down their throats so a machine can breathe for them) for many weeks. As the patient’s body struggles for oxygen, organs essential for life can shut down. Studies show that the majority of patients that are intubated do not make it.

The Washington Post reports that clinicians around the world “are seeing evidence that suggests the virus also may be causing heart inflammation, acute kidney disease, neurological malfunction, blood clots, intestinal damage and liver problems.” There are so many patients in kidney failure in New York hospitals that they have sent out an urgent call for kidney specialists and dialysis machines from around the country.

Aaron Olver, Wisconsin’s former Secretary of Commerce, recently described how he was almost killed by a very similar respiratory virus -- H1N1 -- and how the experience transformed his life. In his 30s, he survived a month of medically induced coma and intubation during which he shed 30 pounds. He recently wrote in an op-ed “I nearly died from H1N1. I can tell you this: social distancing is the best potion we have to fight coronavirus in Wisconsin.” His story can educate us about the significant impacts on his physical and mental health. Patients recovering from COVID-19 tell similar harrowing tales, as you can learn from this National Public Radio report. Doctors are finding that some patients with mild symptoms in their 30s and 40s are suffering from unusual strokes and other complications.

These stories are scary, and a good reminder of how important it is for us to prevent the transmission of this virus. As I wrote about yesterday, the best way to prevent severe cases of COVID-19 is to lower the overall number of cases by preventing transmission. Because we don’t yet have a vaccine, the single best way to prevent transmission is to keep our distance from each other. Hand washing, wearing face coverings, and cleaning frequently touched surfaces are important as well.

We are doing a good job here in Madison so far, but we can’t relax our vigilance against this nasty virus until we have more tools to use in the fight against it. Over the next few days, I’ll be blogging more about some of those tools.

Stay tuned, and follow Public Health Madison & Dane County on Twitter and Facebook for more good information.