A bacterial outbreak at Virginia Mason Franciscan Health in Seattle, Washington, has infected a total of 31 patients, according to a press release on the hospital’s website. 

Four of the 31 patients have died, it's been reported, but public health officials at Public Health - Seattle & King County have not yet confirmed that the infections were a factor in their deaths.

The bacteria has been identified as Klebsiella pneumoniae. The hospital first announced the outbreak in October 2022 and has posted multiple updates, most recently on April 25.

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"Beginning in October 2022, Virginia Mason Medical Center detected an increase in cases of Klebsiella pneumoniae bacteria at our downtown campus," said Sydney Bersante, interim president of the Virginia Mason Medical Center, in a statement on the hospital’s website.

"We immediately implemented increased safety measures, notified patients who had tested positive for the bacteria and promptly provided treatment where necessary," he continued. 

"While the risk of transmission is extremely low for patients, we continue to take proactive steps to avoid additional transmission."

The hospital is working with public health officials to pinpoint the source of the outbreak, Bersante said.

"These types of outbreaks are complex, and despite thorough investigation, we may never know the source," said Dr. Eric Chow, chief of communicable disease epidemiology and immunization public health at Public Health - Seattle & King County, in a public statement. 

Klebsiella pneumonia is a rare cause of infection that is very uncommon in patients with normal immune systems who have not been in the hospital for extended periods of time, Dr. Ken Perry, an emergency physician in Charleston, South Carolina, told Fox News Digital. 

Symptoms of Klebsiella pneumonia are very similar to other common bacterial pneumonias, including fever, chest pain and difficulty breathing, the doctor said. 

"The infection will show up in an X-ray of the chest, and will grow worse the longer the patient remains on the ventilator," said Perry, who is an executive board member of the State Chapter of the College of Emergency Physicians.

The Klebsiella bacteria can cause infections of wounds and surgical sites, as well as pneumonia, bloodstream infections or meningitis, according to the Centers for Disease Control and Prevention (CDC).

"Most of the patients who get K. pneumonia infections have other underlying medical problems that limit their immune systems as well," Perry also said. 

"Although still rare in the general population, it is a common cause of infections in patients who have spent any time on ventilators."

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The infection most often affects sick patients in health care settings who are on ventilators, catheters or extended antibiotic treatments, the CDC stated. 

Healthy people are generally not at risk.

The bacteria is not airborne, the CDC stated.

The infection can also happen in other at-risk patients who are not hospitalized. 

"For these patients, they will have similar symptoms such as chest pain, cough, fever and the textbook answer of ‘currant jelly sputum,’" said Perry. 

"This is a characterization of phlegm that is thick and bloody from the necrosis, or damage, to the lung tissue from the bacteria."

One of the most dangerous aspects of the infection is that some forms of the bacteria are resistant to some antibiotics, which makes it difficult to treat, the doctor warned. 

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This can make it a "life-changing if not fatal infection" for some patients, he said — particularly those who do not have robust immune systems.

"For any hospital that has an increase in this bacteria, the first thing that is necessary is to ensure the eradication of the bacteria from their environment," Dr. Perry said. 

"This means that it will be necessary to deep-clean devices such as air vents, where the bacteria may be able to survive even normal adequate decontamination."