Legionnaires’ Disease: Today and in 1976


Yesterday, Oct. 5 2011, the Maryland Department of Health and Mental Hygiene reported three guests at an Ocean City, Md. hotel were hospitalized and diagnosed with Legionnaires’ disease. It has not been confirmed that the infection occurred at the hotel; tests are ongoing and the hotel has voluntarily closed. 

Legionnaires’ disease is caused by Legionella bacteria. The bacteria got this name because it was discovered in 1976, in American Legionnaires who had attended a convention in a Philadelphia hotel and later reported a mysterious illness.  

Legionella bacteria are transmitted by inhalation of warm, stagnant water that has been aerosolized. This mode of transmission means that the bacteria are more prominent in developed or industrial areas such as near cooling towers, or in hotels, cruise ships and spas. The risk of infection is generally low, as specific criteria need to be met (warm, stagnant and aerosolized water) for the bacteria to be transmitted. Legionnaires’ cannot be transmitted person to person. Those that are at a higher risk for infection are elderly and immunocompromised travelers. 

Symptoms of Legionnaires’ disease are similar to those of pneumonia, and include respiratory problems, cough and high fever. These symptoms may begin anywhere from two to 14 days after exposure to the bacteria. There is no preventive measure against Legionnaires’ disease, but there is antibiotic treatment for the infection.

In 1976, six of the 14 men that first came down with this mysterious illness (later named Legionnaires’) died and, as New York Times stated in a piece marking the anniversary of the discovery of the bacteria, “Americans were primed for the threat of an epidemic.” News of infection in other American Legionnaires and convention attendees spread; the final case count reached 221.  Thirty-four people died. While Centers for Disease Control and Prevention (CDC) epidemiologists investigated the disease, searching for the cause, the public lost faith in health officials.

It wasn’t until months later that an answer was provided. Dr. Joseph McDade discovered that the bacterium causing the illness was actually one that was responsible for illnesses over the past few years. Previous scientists and doctors who had isolated the bactierium believed that it was onlyaffecting animals, not humans, and so it was not linked to the then current outbreak. Today, approximately 18,000 of the hospital admissions each year are related to Legionnaires’ disease. The CDC states that many cases go unreported, perhaps due to the similarities to influenza and pneumonia.

In his New York Times piece, Dr. Lawrence K. Altman emphasizes that the 1976 Legionnaires’ outbreak underlines the importance of communication, not only from the public to the health officials during the onset of illness, but between those engaging in clinical research and those doing the public health investigation:

“Seamless teamwork between epidemiologists and laboratory scientists can be a potent weapon in solving disease outbreaks caused by known and unknown agents” he writes.  

According to Altman, part of the reason that it took so long to discover the source of this illness was the lack of communication between the public health officials who interviewed those that were sick, and the clinicians investigating biologic specimens. Critics complained that more information was coming from the media than from the official health sources. 

Today, we are able to diagnose Legionnaires’ disease by performing a urinary antigen assay. Further, due to improved technology, information systems and social media, the path of communication between the public, the health officials and the clinicians is much clearer. Taking advantage of this may help us stay one step ahead of microbes. 

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