What became known as COVID-19, or the coronavirus, started in late 2019 as a cluster of pneumonia cases with an unknown cause. The cause of the pneumonia was found to be a new virus – severe acute respiratory syndrome coronavirus 2, or Sars-CoV-2. The illness caused by the virus is COVID-19.
Now declared as a pandemic by the World Health Organisation (WHO), the majority of people who contract COVID-19 suffer only mild, cold-like symptoms.
WHO says about 80% of people with COVID-19 recover without needing any specialist treatment. Only about one person in six becomes seriously ill “and develops difficulty breathing”.
So how can COVID-19 develop into a more serious illness featuring pneumonia, and what does that do to our lungs and the rest of our body?
Prof John Wilson, president-elect of the Royal Australasian College of Physicians and a respiratory physician spoke on Australian Television.
“He says almost all serious consequences of COVID-19 feature pneumonia”.
When people with COVID-19 develop a cough and fever, Wilson says this is a result of the infection reaching the respiratory tree – the air passages that conduct air between the lungs and the outside.
He says: “The lining of the respiratory tree becomes injured, causing inflammation. This, in turn, irritates the nerves in the lining of the airway. Just a speck of dust can stimulate a cough.
“But if this gets worse, it goes past just the lining of the airway and goes to the gas exchange units, which are at the end of the air passages.
“If they become infected they respond by pouring out inflammatory material into the air sacs that are at the bottom of our lungs.”
If the air sacs then become inflamed, Wilson says this causes an “outpouring of inflammatory material [fluid and inflammatory cells] into the lungs and we end up with pneumonia.”
He says lungs that become filled with inflammatory material are unable to get enough oxygen to the bloodstream, reducing the body’s ability to take on oxygen and get rid of carbon dioxide.
“That’s the usual cause of death with severe pneumonia,” he says.
“Age is the major predictor of the risk of death from pneumonia. Pneumonia is always serious for an older person and it used to be one of the main causes of death in the elderly.