A culture of the Legionella pneumophila bacteria at a hospital in Belgium.
CNN  — 

A cluster of pneumonia cases in Tucumán, Argentina, was caused by legionella, the bacteria that causes Legionnaires’ disease, the Pan American Health Organization said.

As of Saturday, a total of 11 pneumonia cases had been identified as part of the outbreak associated with a health clinic in the city of San Miguel de Tucumán, including four deaths in patients with underlying health conditions, the organization said.

All cases experienced symptoms of bilateral pneumonia, fever, muscle aches, abdominal pain, and shortness of breath between August 18 and 25 and are epidemiologically linked to the health facility, according to a World Health Organization statement released Monday. Of the 11 cases, eight are health workers of the facility; three are patients of the health facility. Three of the four deaths were among health workers. Four cases were still hospitalized as of Saturday.

Blood, respiratory and tissues samples were obtained from the 11 cases, and preliminary tests conducted at the local Public Health Laboratory were negative for respiratory viruses, and other viral, bacterial, and fungal agents, the WHO statement said.

PAHO said Saturday it was informed by the Argentina Ministry of Health legionella was the cause, and added authorities are now investigating the source.

The ministry is “collecting environmental samples, conducting risk assessments, and implementing actions in the healthcare clinic related to the outbreak,” the update said. “PAHO is providing support to Argentinian health authorities from its Headquarters and the PAHO Country Office in Argentina to investigate and characterize the outbreak.”

The WHO statement said, “Sporadic outbreaks of legionellosis pneumonia have been reported in Argentina before. There are robust surveillance activities being implemented in the affected health facility. Nonetheless, in the absence of an identified source of Legionella bacteria, the risk of developing Legionellosis for people working or hospitalized at the same health facility is currently moderate.”

In its statement, WHO recommends continuing the lab analyses and investigation into the outbreak but does not recommend any specific different measures for travelers or restrictions on travel or trade based on the current information available.

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Legionnaires’ disease is a serious type of pneumonia caused by legionella bacteria. People can get sick when they breathe in small droplets of water containing the bacteria, causing an infection in the lungs. The illness can be treated with antibiotics.

The bacteria can occur in shower heads and faucets, hot tubs, cooling towers, hot water tanks, decorative fountains or plumbing systems in large buildings.

San Miguel de Tucumán is the capital city of the agricultural Tucumán province in northwest Argentina.