Coronavirus leaves the lungs unable to get enough oxygen in and carbon dioxide out of the blood, thus severely affecting breathing

As coronavirus is spreading fast in different parts of the world, scientists are toiling to understand the disease it causes.

Simply put, coronavirus causes respiratory illness.

It may sound simple but the effect the virus has on our body is not.

It starts with cough and fever

Coronavirus multiplies in the lower respiratory tract where symptoms develop.

In the beginning, patients have fever and cough. These are common symptoms that many deal with in the winter season.

The good news is that most people with fever and cough will recover within a few days.

However, about 20 percent go on to develop serious pneumonia as their lungs become inflamed.

Breathing is severely affected

Widespread inflammation in the lungs causes patients to develop Acute Respiratory Distress Syndrome (ARDS).

The main complication in ARDS is that fluid leaks into the lungs, making breathing difficult or impossible.

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Coronavirus leaves the lungs unable to get enough oxygen in and carbon dioxide out of the blood.

"The virus sets up cascading inflammation of organs, and severely inflamed organs cannot do what they are supposed to do," explains Dr Bharat Pankhania of the University of Exeter in the UK.

"It sets up such a huge degree of inflammation that you succumb. It becomes a multi-organ failure."

Cytokine storm

In some of the most severe cases, there can even be a "cytokine storm" in which the immune system goes into overdrive.

When this happens, the immune system overwhelms the body with cells and proteins that destroy other organs.

If the immune system cannot get on top of the virus, the latter will eventually spread to every corner of the body where it can cause even more damage to inflamed organs.

The virus can also stop the kidneys from cleaning the blood and damage the lining of intestines.

Older people, whose immune defence has declined with age, and those with underlying health conditions are much more vulnerable to the virus than the youths.