Pope Francis was treated for double pneumonia, an infection in both lungs, before he died on Monday at the age of 88.
The Holy See has yet to comment on the cause of death. However, Pope Francis was in the hospital for 38 days for double pneumonia until March 23.
The Holy See said at the time the Pope had “polymicrobial infection,” meaning an infection driven by multiple germs.
The infection was one chronic and one acute lung condition, respectively called bronchiectasis and asthmatic bronchitis. Despite this, the Holy See said that the Pope was in “good spirits”.
Pneumonia is an infection that inflames the air sacs in one or both lungs, potentially causing cough, fever, chills, tiredness, and difficulty breathing, according to the UK’s National Health Service (NHS).
It is usually caused by a bacterial, viral infection or a fungus and you can catch pneumonia from someone who already has it.
It can be treated in a couple of weeks with antibiotics among the general population, but it can be a life-threatening condition for older people, babies, and those with heart or lung conditions.
Pope Francis would have been more at risk of lung conditions as he had the upper lobe of his right lung removed when he was in his 20s, due to developing a condition called pleurisy.
The Holy See also said in February that the pope had asthematic bronchitis, which is asthma and acute bronchitis combined.
The incidence of pneumonia in elderly people living at home is estimated to be between 25 and 44 per 1,000 people, which is four times higher than in young adults, according to a study published in 2003.
The disease also leads more often to hospitalisation, higher short- and long-term mortality and a higher risk of complications.
Why are older patients more vulnerable?
The efficiency of the immune system, which is leveraged to fight infection, decreases with age.
The abilities of the respiratory system also weaken as we get older, meaning that coughing, one of the ways the body fights off the infection, is less efficient.
The bacterial flora of the mouth, which is a barrier against pathogens, is also subject to change with time and can be “colonised” by potentially harmful bacteria.
Research shows that only eight per cent of young adults had potentially harmful bacteria in their upper airways, whereas this proportion was 20 per cent among healthy people over the age of 65.
Pneumonia is also harder to diagnose in older people because with the usual manifestations of the disease, such as fever and cough, are often less severe or absent compared to younger patients. Cognitive impairment, apathy and loss of consciousness can be symptoms among older people, potentially delaying the treatment.
Pneumonia can also aggravate existing illnesses.
How can it be prevented?
People over the age of 65 are advised by the NHS to receive two vaccinations because their risk of pneumonia is higher: the flu vaccine and the pneumococcal vaccine.
Both can be administered at the same time.
