The Southern Nevada Health District announced that the number of confirmed Legionnaires’ disease cases has risen to seven – with 29 more cases suspected – five months after an outbreak was originally reported at the Rio All-Suite Hotel and Casino in Las Vegas.

In addition, there were 56 suspected cases of Pontiac fever, which is a flu-like illness caused by Legionella bacteria. Unlike Legionnaires’ disease, Pontiac fever does not cause pneumonia (see below). Those 56 cases bring the total count to 92 confirmed or suspected cases related to the outbreak.

In June, two visitors contracted Legionnaires’ disease after staying at the hotel separately in March and April. Testing of the hotel’s hot-water system in May confirmed the presence of Legionella, which is the bacteria that causes Legionnaires’ disease.

Legionnaires' disease
Legionnaires’ disease basics

“The health district continued to receive notifications of the illnesses from hotel guests who left Las Vegas and were diagnosed in their hometowns,” according to Kimberly Hertin, the SNHD surveillance supervisor.

Cleaning and monitoring the hotel’s water system is ongoing to ensure the eradication of Legionella. All recent tests of the hotel’s water systems showed low levels or no presence of Legionella. A third disinfection took place Nov. 3 as a precaution.

“Guests are not currently at risk for infection,” according to Robert Cole, the SNHD senior environmental health specialist.

“The entire Rio property is open and we have remediated all water sources,” the Rio released in a statement Wednesday. “We continue to work with the Southern Nevada Health Department and have taken the additional step of voluntarily installing a new filtration system to help prevent a reoccurrence.”

Legionnaires’ or Pontiac fever?

Legionnaires’ disease – also called Legionellosis and Legionella pneumonia – is a severe type of pneumonia or lung infection. According to the Centers for Disease Control and Prevention (CDC), an estimated 25,000 cases of pneumonia due to the Legionella bacteria (Legionella pneumophila) occur each year, but only 5,000 cases are reported because of the disease’s non-specific signs and symptoms. In addition, 10 percent of those cases will end in death.

Pontiac fever, on the other hand, can produce symptoms including a fever, chills, headache, and muscle aches. Pontiac fever, however, doesn’t infect the lungs.

Legionella in the air 

Legionella bacteria are contracted by inhaling microscopic water droplets, generally in the form of mist or vapor. The bacteria, which grow best in warm water, are found primarily in human-made environments.

Outbreaks have been linked to a range of sources, such as:

  • water systems, such as those used in hotels
  • cooling towers in air-conditioning systems
  • decorative fountains
  • mist machines
  • hot tubs/whirlpools
  • hot-water tanks and heaters
  • large plumbing systems
  • showers and faucets
  • swimming pools.