Mystery Disease in the 20th Century – A Look at the First Outbreak of Legionnaires

By Visio Roughton

Modern medicine has made notable growths in terms of its ability to track and treat diseases, however, there was a time when this was not the case, and it was incidents such as the Legionella outbreak that rattled through Philadelphia in the summer of 1976. What superficially appeared to be nothing more than a gathering of military veterans quickly became a public health crisis, as dozens of individuals —both attendees of the veteran’s gathering and people unassociated with the event— were sickened by a severe pneumonia-like illness. With no clear answer pointing to what was causing the sudden and rising death toll of those afflicted, fear and speculation ran rampant through the community. What followed this wave of the mystery illness was one of the most perplexing epidemiological investigations in modern history, ultimately leading to the discovery of an entirely new bacterial disease; one, researchers found, that had been hiding in plain sight.

Birth of a Mystery Illness:

On July 21, 1976, An annual three-day convention began at the Bellevue-Stratford Hotel in Philadelphia, Pennsylvania. This convention was hosted by the American Legion, more commonly referred to as ‘The Legion’. The Legion, founded in Paris, France after the conclusion of WW1, is a non-profit organization for U.S. veterans. While their headquarters are in Indianapolis, Indiana, they decided to host the convention in Philadelphia that year to honor the two-hundredth anniversary of the signing of the Declaration of Independence. 

The convention itself was executed smoothly, and it wasn’t until the veterans returned to their respective homes did it become apparent that they had come in contact with a mysterious illness during their time at the event.

Three days after the conclusion of the convention, 61-y/o Legionnaire Ray Brennan died suddenly at his home of what was ruled a heart attack by medical examiners after experiencing severe exhaustion since his return. On July 30th, Frank Aveni also died of a supposed heart attack. Less than twelve hours later, six more legionnaires died of the mysterious illness. Their similarity in symptoms (exhaustion, chest pains, lung congestion, and fever.) led doctors to believe that they were not dying of cardiac events, but rather an illness. 

Theories and Speculation:

All of these men were connected by one thing: the fact they had all been guests at the Bellevue-Stratford Hotel during the Legion convention. It is important to note, that not only people from the convention were getting ill. Many guests of the Bellevue-Stratford Hotel, and even people who did not enter the hotel but simply passed by, were stricken by this illness. 

With a breakout of swine flu earlier that year, and no answer as to why all these people were falling victim to this mysterious pneumonia-like sickness, people began to panic. The illness was reported to the Centers for Disease Control, however even they had no answers as to where this disease was coming from, and if there was a cure. Due to the lack of strong leads, it took many months of investigation before an answer was reached, and during that time, endless news coverage brought even more fear to the country. The public was terrified and had no answers, thus began to speculate the cause.

Perhaps it was metal poisoning from the cadmium jugs used to serve water at the meeting, or perhaps there was something on the microphone used? Some even wondered if a guest of the hotel had smuggled in an exotic pet that was a vector for the disease, as parrots especially are known to be vectors of illness. All these theories were proved to be false. Some of the wildest theories consisted of many things from a possible bioterrorism attack, all the way to aliens, however, this also was incorrect. Despite all of these theories, one fact became known quite quickly: whatever the cause, the Bellevue-Stratford Hotel was most likely ground zero for this outbreak. 

In January 1977, after injecting lung tissue from infected veterans into guinea pigs, Dr Joseph McDade noticed the presence of a new, and at that point unknown, bacteria in the livers of the guinea pigs. After much more extensive testing and research, McDade figured out that he had, at last, found the cause of the outbreak. Scientifically named Legionella Pneumophila, it had infected many members of the American Legion, thus scientists and investigators in the field were already referring to it as “Legionnaires  Disease.” 

A Name to the Illness: 

The Bacteria Legionella Pneumophila and its less severe relative “Pontiac Fever” tend to breed freely and violently in hot standing water, or cooling tanks, among many other places. Although it only occurs naturally in lakes and ponds, it can get washed into main water supplies or carried by droplets of water vapor. This is a conclusion that CDC investigators reached, and as a result, they were able to trace the infection back to the Hotel’s cooling tower, which was connected to the A/C throughout the building. Specifically, the Legionella was breading in a pool of standing water that had collected in the cooling tower. As it is not a transmissible bacteria, a person must breathe in water vapor from contaminated sources over a significant amount of time, and it was revealed that, indeed, during the hot summer, this illness was transmitted through the whole building via the air conditioners. 

With this discovery, investigators were also able to connect Legionella to several other smaller outbreaks in years past which, until the discovery of the disease, did not have an identified source. Interestingly, one of these happened to be a much smaller outbreak that also occurred in the Bellevue-Stratford Hotel.

This incident inspired new maintenance regulations for air conditioners, cooling tanks and large water systems, which all building managers and owners must adhere to. 

Like with most diseases, it can take many years of tireless and meticulous research and testing to find cures and treatments for illnesses. Today, water treatment regulations are followed to lower the chances of an outbreak. Legionella itself is easily detectable, and can typically be treated with antibiotics. More understanding has led to treatments for Legionella, and with this in mind, it is a comfort to know that we finally have an answer, and people will no longer have to live in fear of the mysterious pneumonia that infected so many people, back in the summer of 1976.