Legionnaires' disease was once unknown to the general public, but it's since become one of the most dreaded afflictions in recent memory after a high-profile case surfaced a few decades ago and the CDC became involved in studying the illness. The specific strain of pneumonia is incredibly harmful and killed dozens in the high-profile incident that helped it seize the public's attention. Nonetheless, many know little about Legionnaires' disease and how it works to degrade our health.

Even fewer people understand why it loves water, and how it can be avoided. Here's why Legionnaires' disease loves water, and what else you need to know about this terrible illness.

Learning about Legionella bacterium

Legionella bacterium was first discovered by the American CDC after a virulent strain of it was spread through a hotel air condition system, impacting hundreds and killing dozens. When two or more people are exposed to Legionella bacterium at the same time, they can also contract Pontiac fever, a related illness that's less serious but nonetheless still grave and uncomfortable in its own right. Oftentimes, structures with complex water systems like a hotel or a resort are susceptible to transmitting legionella bacterium because it thrives in water.

Water used for showering, hot tubs, swimming, drinking, and cooling towers can all be used to transmit Legionella bacterium under the right circumstances, meaning many people can quickly be impacted by the disease in a very brief period of time. After a convention at an American Legion in Philadelphia in 1976, authorities were left puzzled by a Legionnaires' outbreak that proved to be quite disruptive to public health at the time. Many people feared going out in public and sharing water with others for a short period after it became clear that Legionella bacterium was spreading through water.

Another reason that Legionnaires disease  is so frightening is because it's a very underreported disease. The CDC indicates that at least 6,100 cases of Legionnaires' were reported in the US in 2016, for instance, but that figure is likely to be much lower than the actual number of outbreaks. Many people are unfamiliar with the symptoms and consequences of Legionnaires', making it important to review fact sheets surrounding the disease.

Why it loves water

Legionella bacterium loves water for a simple reason - it helps the disease spread. Breathing in small droplets of water is how legionella bacterium is mostly spread from one person to another, with a compromised water distribution system often being the root source of the issue. Such a compromised system was the reason that one Philadelphia hotel suffered an outbreak that killed dozens, leading to the name of Legionnaires' as we recognize it today. The bacterium can also thrive in natural water sources such as rivers and lakes, however, so it's important to establish that not only artificial water systems like pools, hot tubs, and water towers can host the disease.

Mist machines, humidifiers, and other everyday tools can be used to spread Legionella bacterium unknowingly. A comprehensive review of water sources that can transmit the disease is in order for anyone who wants to truly understand it and how to avoid contracting it in the future. In recent years, Flint, Michigan and its well-published water crisis has ignited renewed interest in the possibility of Legionnaires' outbreaks that could claim lives.

Areas of the city that had lower levels of free chlorine in the water were notably more susceptible to Legionnaires' outbreaks than others, according to recent research, indicating that public funding could be needed to prevent future outbreaks in other urban environments. As long as shared water sources continue to become compromised, Legionnaires' disease will keep spreading into the population.