What Does Coronavirus Do to the Body?

What Does Coronavirus Do to the Body?

March 12,2020

As cases of coronavirus infection proliferate around the world and governments take extraordinary measures to limit the spread, there is still a lot of confusion about what exactly the virus does to people’s bodies.
The symptoms — fever, cough, shortness of breath — can signal any number of illnesses, from flu to strep to the common cold. Here is what medical experts and researchers have learned so far about the progression of the infection caused by this new coronavirus — and what they still don’t know.

 How does this coronavirus cause infection?

The virus is spread through droplets transmitted into the air from coughing or sneezing, which people nearby can take in through their nose, mouth or eyes. The viral particles in these droplets travel quickly to the back of your nasal passages and to the mucous membranes in the back of your throat, attaching to a particular receptor in cells, beginning there.

Coronavirus particles have spiked proteins sticking out from their surfaces, and these spikes hook onto cell membranes, allowing the virus’s genetic material to enter the human cell.
That genetic material proceeds to “hijack the metabolism of the cell and say, in effect, ‘Don’t do your usual job. Your job now is to help me multiply and make the virus,’” said Dr. William Schaffner, an infectious disease specialist at Vanderbilt University Medical Center in Nashville.

How does that process cause respiratory problems?
As copies of the virus multiply, they burst out and infect neighboring cells. The symptoms often start in the back of the throat with a sore throat and a dry cough.The virus then “crawls progressively down the bronchial tubes,” Dr. Schaffner said. When the virus reaches the lungs, their mucous membranes become inflamed. That can damage the alveoli or lung sacs and they have to work harder to carry out their function of supplying oxygen to the blood that circulates throughout our body and removing carbon dioxide from the blood so that it can be exhaled.

What trajectory does the virus take in the lungs?
Dr. Shu-Yuan Xiao, a professor of pathology at the University of Chicago School of Medicine has examined pathology reports on coronavirus patients in China. He said the virus appears to start in peripheral areas on both sides of the lung and can take a while to reach the upper respiratory tract, the trachea and other central airways.

Dr. Xiao, who also serves as the director of the Center For Pathology and Molecular Diagnostics at Wuhan University, said that pattern helps explain why in Wuhan, where the outbreak began, many of the earliest cases were not identified immediately.
The initial testing regimen in many Chinese hospitals did not always detect infection in the peripheral lungs, so some people with symptoms were sent home without treatment.

Are the lungs the only part of the body affected?
Not necessarily. Dr. Compton-Phillips said the infection can spread through the mucous membranes, from the nose down to the rectum.So while the virus appears to zero in on the lungs, it may also be able to infect cells in the gastrointestinal system, experts say. This may be why some patients have symptoms like diarrhea or indigestion. The virus can also get into the bloodstream, Dr. Schaffner said.The , but that it’s unclear whether infectious virus can persist in blood or stool.

“The virus will actually land on organs like the heart, the kidney, the liver, and may cause some direct damage to those organs,” Dr. Schaffner said. As the body’s immune system shifts into high gear to battle the infection, the resulting inflammation may cause those organs to malfunction, he said.As a result, some patients may endure damage that is inflicted not just by the virus, but by their own immune system as it rages to combat the infection.

Why do some people get very ill but most don’t?
About 80 percent of people infected with the new coronavirus have relatively mild symptoms. But about 20 percent of people become more seriously ill and in about 2 percent of patients in China, which has had the most cases, the disease has been fatal.Experts say the effects appear to depend on how robust or weakened a person’s immune system is. Older people or those with underlying health issues, like diabetes or another chronic illness, are more likely to develop severe symptoms.

What do scientists still not know about coronavirus patients?
A lot. Although the illness resembles SARS in many respects and has elements in common with influenza and pneumonia, the course a patient’s coronavirus will take is not yet fully understood.Some patients can remain stable for over a week and then suddenly develop pneumonia, Dr. Diaz said. Some patients seem to recover but then develop symptoms again.Dr. Xiao said that some patients in China recovered but got sick again, apparently because they had damaged and vulnerable lung tissue that was subsequently attacked by bacteria in their body. Some of those patients ended up dying from a bacterial infection, not the virus. But that didn’t appear to cause the majority of deaths, he said.Other cases have been tragic mysteries. Dr. Xiao said he personally knew a man and woman who got infected, but seemed to be improving. Then the man deteriorated and was hospitalized.