An outbreak of inexplicable deaths at an American Legion convention in 1976 sparked a frantic search for the cause.
21st July 1976 is a pivotal date in the history of Legionnaires Disease (Legionella pneumophila). Medical history suggests the organism had been the cause of mortality prior to its official categorisation, but the US Bicentennial Convention of the American Legion in Philadelphia proved the catalyst for its official recognition.
Bellevue Stratford Hotel
The Bellevue Stratford Hotel was host to the 58th convention of the American Legion in July 1976 and within a day visitors began to feel unwell. The symptoms of coughing, fever and breathing difficulties were not considered unusual given that over 4000 Legionnaires and their friends and families were in attendance, but by July 27th the first death had been reported.
Events at the beginning of the year were to play a part in the unfolding story of Legionnaires Disease.
1976 US Influenza Epidemic
In January 1976, an influenza epidemic struck the United States. Nine unidentified viruses were isolated, five of which were recognised as from the common influenza A strain. Four, however, were identified as swine influenza viruses.
This caused great concern, as a pandemic caused by human-to-human transmission of this form of virus led to millions of deaths in 1918. This fear was compounded when sera taken from the initial outbreak indeed indicated human-to-human transmission.
The then President, Gerald Ford, came under pressure to implement a vaccination programme to ward off a potential pandemic. As the year progressed however no new strain of virus was apparent, and a stand-off ensued between insurance companies and vaccine manufacturers.
The insurance companies would not insure the manufacturers and the manufacturers would not produce vaccine without insurance. Reports then emerged of people dying from flu-like symptoms who had attended the convention in Philadelphia.
Influenza or Legionnaires’ Disease?
By early August, intense investigations were underway to discover the cause of death of the Legionnaires. Tests did not indicate influenza but Congress, sensitive to possible media criticism and wary of being seen to impede the process of potentially life saving immunisation, swiftly passed the Tort Claim Act.
This act was to indemnify pharmaceutical companies against claims arising from the immunisation programme and had initially been stalled in Congress.
The Mystery Killer
With the influenza pandemic failing to materialize, media interest grew in the Legionnaires’ plight. Of the 221 infected, 34 had subsequently died and the inability of the authorities to confirm a cause was causing frustration and concern.
This led to some wild allegations to surface. Nickel carbonyl intoxication was mooted as a cause; conspiracy theorists suggested communists or pharmaceutical companies were systematically murdering American veterans.
The Answer to the Riddle of Legionnaires Disease
Working late in December 1976, Dr Joseph McDade returned to his laboratory to tidy up his testing before the year’s end. Taking a fresh look at a specimen slide, he noted a cluster of bacilli was engulfed by a white cell.
Reacting to the find, he altered the procedural testing and was subsequently able to isolate the relevant bacteria. Legionnaires Disease had been found.
In fact, the bacterium had been previously isolated by researchers as early as 1947 but was thought to only affect animals and not humans.
In hindsight an important factor in the search was overlooked. Of the 221 people originally infected, 72 were not even involved in the convention. When it was discovered the organism resided in the water of cooling towers, it was realised that the bacterium was spread by the air-conditioning system in the form of aerosolised water droplets. Once inhaled the microorganisms multiplied and produced the potentially fatal disease.
Further Outbreaks of Legionnaires Disease
Further outbreaks of Legionnaires Disease have been consistently reported since the convention of 1976, with the largest outbreak in Spain with 449 confirmed cases, resulting in 6 fatalities.