What is Legionnaires Disease?

In July of 1976 a military veterans association, the American Legion, gathered for their annual convention in a Philadelphia hotel. Within two days members of the convention began to fall ill with a variety of symptoms such as fevers, chills, coughing, and fatigue. In the span of a few weeks, over thirty of the Legionnaires would be dead, and over two hundred more hospitalized.

It took doctors, scientists and a myriad of public health officials months to determine what had caused the deaths of so many in such a short time. In the end, a new bacteria was identified as a the cause of the disease. Although the bacteria almost certainly existed prior to its identification in 1976, it was aptly named Legionella pneumophilia.

Legionnaire's Disease is a type of pneumonia. Like all pneumonias, the disease causes damage to the tiny sacs in the lungs where air is passed in to the bloodstream. These sacs, called alveoli, become filled with fluid due to this damage and cause the infected person to become quite sick.

Persons who become infected with Legionella will experience a wide range of symptoms. Coughing, fatigue, fever, aching muscles and chills are the most common presentations. In addition, some people will complain of vomiting. Legionnaire's Disease is more common in older persons, or people with compromised immune systems, such as HIV patients. There is also an increased risk for people who are long time smokers or have other lung problems, such as chronic bronchitis.

Distinguishing Legionnaire's Disease from other bacterial causes of pneumonia can be quite a challenge for a doctor. Typically a doctor will look for the bacteria in a sample of the patient's sputum, which is the gunky junk you tend to cough up when you have a pneumonia. Chest X-Rays will also show evidence of the infection, although the X-Ray alone cannot be used to distinguish Legionella from any other type of pneumonia.

The route of spread of this disease follows an interesting pattern. The Legionella bacteria grow well in water, and can easily contaminate any water supply they are exposed to. The bacteria then multiply, awaiting the chance to find a human host. Many outbreaks, including the 1976 American Legion Convention, have been caused by contaminated air conditioning units, which spread tiny droplets of infected aerosolized water around large indoor spaces. Water cooling towers, room humidifiers, and even jacuzzis can be a reservoir for the bacteria.

A lesser form of the infection, known as Pontiac Fever occurs when a patient is infected with the legionella bacteria and shows symptoms of fever and muscle aches, but no associated pneumonia. Pontiac fever is generally self-limiting and patients are much quicker to recover compared to a case of full blown Legionnaire's Disease.

Treatment for Legionnaire's disease involves the use of antibiotics. The most effective antibiotics are in the quinolone or macrolide families, specifically Levaquin (levofloxacin) or Zithromax (azithromycin). Rifampin is sometimes added in combination with these medications to create a synergistic effect. Penicillins have been found to be less effective, as well as cephalosporins. If antibiotic therapy is started early, a vast majority Legionnaire's Disease patients can be cured effectively However, it can still be fatal in some severe cases despite aggressive treatments. The lesser form, Pontiac Fever, does not generally require antibiotics.