Is Legionnaires’ Disease Contagious? This simple answer is …

The simple answer to this question is no, Legionnaires’ disease is not contagious. It is caused when waterborne legionella bacteria are transmitted to humans when they inhale mist or droplets from contaminated water. When someone develops Legionnaires’ disease, they will have flu-like symptoms, but they will not pass the disease on to other people in the same way as they do with the flu or a cold. 

Legionnaires’ disease is, however, classified as an infectious disease. 

The difference between an infectious disease and a contagious disease

An infectious disease is caused by bacteria or viruses that get transferred into the body – in the case of Legionnaires’ disease, this is through the respiratory system. A contagious disease is an infection that’s passed on to other people through proximity, touch or bodily fluids. Sneezing and coughing allows infectious germs to travel from one person to another, as does touch, kissing, etc. Colds and flu are the most common contagious diseases, and thanks to Covid-19, it has become very well known that you can significantly reduce the risk of being infected by maintaining good hygiene practices such as washing your hands and using anti-bacterial cleaning products, as well as distancing yourself from an infected person. 

Legionnaires’ disease is not contagious, meaning no extra precautions need to be taken by those around the patient. However, as the symptoms of Legionnaires’ disease – cough, fever, muscle ache, loss of appetite, fatigue – are similar to the symptoms of flu and Covid-19, it’s unsurprising that people question whether or not it’s contagious.

Who is most at risk from the legionella bacteria? 

People who are younger and have no other health conditions are less likely to develop Legionnaires’ disease, even if they come into contact with the legionella bacteria. The elderly are particularly at risk, and the majority of reported fatalities are people in their seventies and eighties. However, you begin to become more vulnerable after the age of 45. Smokers and heavy drinkers are also at higher risk, as are people who suffer from diabetes and those with chronic respiratory problems, heart disease or kidney disease. 

How does water become contaminated with the legionella bacteria? 

Legionella bacteria are found naturally in freshwater lakes, streams and rivers, though usually in such low numbers they don’t pose a particular risk. Problems begin when the bacterium is allowed to grow and thrive in man-made water systems, such as cooling systems, water systems in domestic or commercial premises, or water features such as shower heads, taps, water features, etc. 

The optimum condition for the spread of legionella is stagnant water that’s between 20°C and 45°C. Because of this temperature, measured with a legionella thermometer, legionella is a particular problem when it comes to hotels, spas and leisure centres that are more likely to have hot tubs, saunas and steam rooms. There is also a danger when water has been left dormant for a while, which is why so many businesses asked us to carry out water testing before staff returned to their premises after the lockdowns. 

Under the Health and Safety at Work Act 1974, employers and duty holders must ensure the health and safety of their employees and visitors who may be affected by legionella. Ask us about the benefits of a legionella risk assessment where our experts will conduct a detailed examination of your premises and advise on the best actions to take to decrease the chances of legionella bacteria causing an outbreak of Legionnaires’ disease.