How does the Wuhan coronavirus cause severe illness?

Wuhan Coronavirus Cause Severe Illness

We generally consider viral respiratory infections, such as the common cold, as mild nuisances that pass within a few days. But Wuhan's coronavirus turned out to be different. Among those infected, about 2% are believed to have died, but the true mortality is unknown.

There is still a lot to learn about this new virus, but we know that it often causes pneumonia, an infection of the lungs that produces pus and fluid and reduces the ability of the lungs to absorb oxygen.

Of the first 99 severely infected people, three-quarters had pneumonia affecting both lungs. About 14% appeared to have lung damage caused by the immune system, while 11% suffered from multi-organ system failure, or sepsis.

Others are at risk of complications from treatment in hospitals, such as acquiring other infections.

At this point, we know that some people only develop a mild infection, while others become seriously ill, but the exact proportion of each is not yet clear.

Overall, Wuhan coronavirus can cause four serious illnesses in four key ways, and some can happen at the same time.

Direct viral damage

For SARS (severe acute respiratory syndrome) coronavirus, direct viral damage was probably the most common way in which infection caused disease. This is probably the case with Wuhan coronavirus.

Initial studies have revealed that Wuhan coronavirus attaches to a particular receptor found in lung tissue. It is like a locking and key mechanism allowing the virus to enter the cell, and it is the same receptor as the SARS coronavirus used.

Viruses "hijack" the mechanisms of the host cell to create more copies of itself. The damage results either from virus completely invading the cell and killing it, or from immune cells recognizing the viral infection and mounting a defense, triggering cell death.

If a large number of cells die, the affected organ cannot function effectively.

Studies of patients who have died from the SARS coronavirus have shown that the virus damages not only the lungs, but also other organs of the body. Initial research suggests that Wuhan coronavirus can also damage other organs, including the kidneys.

Pneumonia

While we are still in the process of reconstructing the relationship between Wuhan coronavirus and pneumonia, we can learn a lot from the flu.

Influenza is a virus but it usually leads to bacterial pneumonia - this is called a secondary infection.

The flu virus is thought to weaken the lung's usual protective mechanisms, allowing bacteria to establish and multiply. This is especially true in children, the elderly and those with weakened immune systems.

Secondary bacterial pneumonia is more serious than the flu alone - in hospital patients, about 10% of people with flu and pneumonia die, compared to about 2% of those without pneumonia.

Wuhan's coronavirus appears to cause pneumonia in two ways: when the virus gets into the lungs and through secondary bacterial infections, however, the first method seems to be more common.

Sepsis

Sepsis is a serious illness that can be caused by many infections.

When we get an infection, we need to develop an immune response to fight the pathogen. But an excessive immune response can cause organ damage and failure. This is what happens in case of sepsis.

Although it may be difficult to determine whether the organ damage caused by Wuhan coronavirus is the result of a direct viral infection or indirect "collateral damage" to the immune system, early reports have suggested that about 11% severely ill people with Wuhan coronavirus have experienced organ failure.

To date, no drug or intervention has been able to mitigate this immune response. Although several treatments have been proposed for Wuhan coronavirus, none have yet demonstrated its effectiveness.

Complications of hospital care

Finally, patients requiring hospital care may have complications. These include intravenous tract infections (for drops / medication) or urinary catheters (flexible tubes inserted into the bladder to empty urine), pneumonia, or non-infectious complications such as falls or bedsores.

Studies have found that 10% of hospital patients suffer from some sort of healthcare-acquired infection, and about 5% have a pressure ulcer.

Hospitals work hard to try to prevent these complications, by ensuring that health workers disinfect their hands and other equipment. However, complications persist, especially in patients weakened by long hospital stays.

While most viral respiratory infections are mild, some can trigger serious complications, directly or indirectly. It is too early to say how often this happens with Wuhan coronavirus. Although we have initial data on the severely affected, many others may not have required medical attention.