Pneumonia is a potentially deadly condition caused by inflamed tissue in one or both lungs.

The infection damages the delicate lining of this organ, causing tissues to swell and fluids to leak into the fine network of channels and air sacs – called alveoli – where oxygen and carbon dioxide molecules are exchanged.

Symptoms can include a cough that produces significant amounts of greenish or even bloody mucus, shortness of breath or increased breathing rate, appetite loss, chest pain, and fever.

More than two and a half million people around the globe died from pneumonia in 2017. Around a third of those were children, making it one of the leading causes of deaths for those under the age of five, especially in developing nations.

Seniors also experience a high mortality rate. During the same period, more than a million deaths occurred among those over the age of 70.

In nations such as the US, out of around one million people seeking medical attention for the condition each year, roughly 50,000 won't survive.

What causes pneumonia?

A variety of afflictions and infections can put individuals at risk of pneumonia.

Infectious bacteria (such as Streptococcus pneumoniae), viruses (like the coronavirus SARS-CoV-2), or fungi (like species of Aspergillus), can damage the lung's tissues, prompting an immune response. Inhaling fluids, in what is referred to as aspiration, can also cause a similar reaction.

Complications, including death, can develop from lack of oxygen or in many cases septicaemia (blood poisoning).

People with cystic fibrosis, asthma, or autoimmune conditions are especially at risk from pneumonia, as are smokers. Long periods spent on a hospital ventilator can also increase the chances of developing this infection.

Can you 'catch pneumonia' by being too cold?

When your parents told you this, they actually might have been on to something. Not only could a lower body temperature predispose you to catching more colds, but cold, dry air is seriously bad for your lungs.

Studies that directly investigate links between chest infections and cold weather find there is a link.

A Finland study on children with pneumonia, for instance, found around a quarter also had a rhinovirus; a virus associated with the common cold. While this doesn't mean being cold is a one way trip to a stay in hospital, it should make you want to rug up a little tighter. Just in case.

How is pneumonia treated?

It's important that patients with pneumonia receive sufficient oxygen and hydration, which is why most people diagnosed with the condition find themselves in hospital.

Bacterial infections can respond well to antibiotics if caught early, although there has been a marked rise in drug resistant strains in recent years.

There are also medications for viral infections, and fungal infections, which may also require surgical intervention.

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