Many people are exposed to Legionella, but their bodies’ defence systems respond to prevent illness. Although previously healthy people may develop Legionnaires’ disease (LD), there are several factors that have been shown to increase an individual’s susceptibility, including: increasing age; being male; being a smoker; having an existing respiratory disease; and pre-existing illness, such as cancer, diabetes, kidney disease or alcoholism.
Susceptible people who inhale very small droplets of water contaminated by Legionella can develop a form of pneumonia, which can be fatal. Several conditions must be met for this to occur: the Legionella must be virulent and present in sufficient numbers to cause infection; it must be carried to the host without too much injury during transport; it must reach the deepest part of the lungs; and the host’s defence system must be unable to stop the infection.
Lower respiratory infections remain one of the top global causes of dean and the emergence of new diseases continues to be a concern. At the start of the 21st century, we have borne witness to the emergence of newly recognised coronaviruses that have rapidly spread around the globe.
Although we perhaps most frequently think of viruses when discussing emerging respiratory infections, bacteria have not been left out of the mix, as we have witnessed an increase in the number of infections from Legionella’. European data reported by Cunha et al suggests that LD is substantially under-diagnosed and under-reported. fewer than 5% of cases are being reported.