• Coronaviruses cause respiratory diseases and so the lungs are generally first affected.
• Early signs include fever , cough and breathlessness. Upon exposure to the virus these occur as early as 2 days, or as long as 14 days.
• But injury, particularly during serious illness, can also occur in other parts of the body.

There’s still a lot we don’t know about the latest coronavirus that has been sickened by more than 3.2 million deaths worldwide, with over 230,000 reported.

Yet one thing that’s clear is that the virus can have a debilitating effect on the body — and not just on the lungs, in serious cases.

Here’s what we know so far about how COVID-19, the disease which causes the new coronavirus, affects the various systems in the body.

COVID-19 affects lungs

As with other diseases of coronavirus — including SARS, MERS and common cold — COVID-19 is a respiratory disease, so the lungs are usually first affected.

Early signs include fever , cough and breathlessness. Upon exposure to the virus these occur as early as 2 days, or as long as 14 days.

Although fever is at the top of the list of symptoms in the Centers for Disease Control and Prevention, not everyone who gets sick has a fever. In one study in the Journal of the American Medical Association, researchers found that around 70 percent of patients hospitalized with COVID-19 didn’t have a fever.

Cough is more common but treatment guidelines developed by Brigham and Women’s Hospital in Boston found that cough occurs in 68 to 83 percent of people who show up with COVID-19 at the hospital.

Only 11 to 40 per cent had breath shortages.

Other symptoms less common include confusion, headache , nausea and diarrhea.

COVID-19 ‘s severity varies from mild or no symptoms to severe or at times fatal illness. Data on over 17,000 reported cases in China revealed that nearly 81 percent of cases were mild. The remainder were serious or critical.

Older people and those with chronic medical conditions tend to be at higher risk for severe illness.

Also reveals this variation in how COVID-19 affects the lungs.

Some people may have only mild respiratory symptoms while others may experience pneumonia that is non-life-threatening. But there is a subset of people who develop severe damage to their lungs.

“What we sometimes see in patients with [COVID-19] is a disease we call acute respiratory distress syndrome, or ARDS,” said Dr. Laura E. Evans, a member of the Critical Care Medicine Leadership Council and an associate professor of pulmonary, critical care and sleep medicine at the University of Washington Medical Center in Seattle.

ARDS isn’t just happening with COVID-19. A number of events can trigger it, including infection, trauma, and sepsis.

These cause lung damage, which contributes to the leakage of fluid from small blood vessels in the lungs. The fluid contains air sacs, or alveoli, in the lungs. That makes transferring oxygen from the air into the blood difficult for the lungs.

Although knowledge about the type of damage that occurs in the lungs during COVID-19 is missing, a recent study indicates it is close to the damage caused by SARS and MERS.

One longitudinal study of 138 people hospitalized for COVID-19 showed that on average, after displaying symptoms, people started having trouble breathing 5 days. On average, ARDS developed 8 days after symptoms.

ARDS treatment requires extra oxygen and mechanical ventilation, with the goal of bringing more oxygen into the blood.

“There is no treatment unique to ARDS,” said Evans. “We just help the individual as best we can during this process, helping their bodies to recover and their immune system to cope with the underlying events.”

One curious thing about COVID-19 is that many patients have potentially dangerous low levels of oxygen in the blood, but do not appear to be desperate for oxygen. This has led some doctors to rethink putting patients on a ventilator simply because of low oxygen levels in the blood.

Other organs affected by COVID-19

The lungs are the principal organs that COVID-19 affects. But in extreme cases it can affect the rest of the body as well.

In extreme cases it may also impact the rest of the body.

“A large proportion of such patients often experience dysfunction in other organ systems in patients who are critically ill,” Evans said.

She says this can happen with any serious infection though.

This damage to the organs isn’t always directly caused by the infection, but can result from the body’s response to infection.

Stomach and intestines

Some people with COVID-19 reported gastrointestinal symptoms, such as nausea or diarrhea, but these symptoms are much less common than lung problems.

Though coronaviruses tend to have an easier time entering the body through the lungs, these viruses don’t have the intestines out of control.

Earlier reports identified the viruses in the intestinal tissue biopsies and stool samples which cause SARS and MERS.

Two recent studies — one in the New England Journal of Medicine and a preprint on medRxiv — report that some people with COVID-19 have tested positive for the virus in stool samples.

However, researchers do not yet know if this virus can be transmitted fecally.

Heart and blood vessels

Evans says that COVID-19 will influence the heart and blood vessels, too. These can occur as abnormal heart beats, not enough blood to get to the tissues, or low enough blood pressure that medication is needed.

So far, however, it’s not obvious whether the virus affects the heart directly.

20 per cent had some form of heart damage in one study of hospitalized patients in Wuhan. In another, 44 percent of those in an intensive care unit (ICU) had an irregular heart rhythm.

Liver and kidneys

When liver cells are inflamed or damaged, they can leak into the bloodstream higher than normal enzyme levels.

Elevated liver enzymes aren’t necessarily a sign of a serious problem, but in people with SARS or MERS this laboratory result was seen.

In one study of hospitalized COVID-19 patients in Wuhan, 27 percent had kidney failure.

One recent report found a person with COVID-19 showing signs of liver damage. Doctors says it’s not clear, though, if the vi

Some people who were hospitalized with COVID-19 often suffered acute kidney damage and sometimes needed a kidney transplant. This happened with SARS and MERS too.

Scientists have found the virus which causes this disease in the tubules of the kidneys during the SARS outbreak.

However, there’s “little evidence” to show that the virus caused the kidney injury directly, according to a report from the World Health Organization.

Dr. James Cherry, a pediatrics research professor at UCLA’s David Geffen School of Medicine, says the kidney damage may be due to other changes that occur during infection with coronavirus or the drugs being used to treat the person caused the damage.

“You have less oxygen circulating when you’re having pneumonia,” he said, “and that can damage the kidneys.”

Immune system

The body’s immune system responds to any infection by attacking the foreign virus or bacteria. While this immune response can rid the infection’s body, it can also occasionally cause collateral damage to the body.

This can come in the form of an extreme inflammatory response, often called a “cytokine storm.” Cytokines are formed by the immune cells to combat infection, but if too many are released, they can cause body problems.

“Much [the body damage during COVID-19] were due to what we’d call a sepsis syndrome, which is due to complex immune reactions,” said Evans.

“The infection itself can produce an intense inflammatory response in the body that can affect multiple organs system function.”

Another thing about the immune system is that there are practically no cases of COVID-19 in children under the age of 9 so far. Scientists aren’t sure whether young children don’t get sick or whether their signs are so mild that nobody knows.

Cherry says children still experience less serious illness during certain forms of illnesses, including measles and pneumococcal illnesses than adults do.

He says this can be because children have a “straightforward immune response,” while older people may sometimes have a “over-response.” It’s this excess immune response that causes some of the damage during infections.

“There was evidence of this happening during SARS,” Cherry said, “and I suspect it could also be playing out here [with COVID-19].”