The city announced Monday that, since an outbreak in late July, 108 people have been infected with Legionnaire’s disease, a type of pneumonia that spreads through bacteria lurking in warm later.

Legionnaire’s disease mimics the flu before progressing to pneumonia, with patients suffering symptoms such as high fever, breathing trouble, and even mental confusion.

This is up from 99 cases last week, a nine percent increase. Hospitalizations are down from 17 to 14.

Legionnaires’ disease is caused by Legionella bacteria, which thrive in warm water and can become airborne when water turns to steam. While the disease can also be spread by air conditioners, New York officials said they are not the source of the current outbreak.

Legionnaires’ is most severe in older people, smokers and those with chronic lung diseases.

All cases and deaths have been reported in five ZIP codes covering the Harlem, East Harlem and Morningside Heights neighborhoods.

The New York City Health Department said Monday that the newly-reported death had been ‘under investigation for some time and our team was able to confirm this death as part of the cluster today.’

The announcement came after the last of 12 cooling towers that had tested positive for Legionella was treated and disinfected on Friday.

Mayor Eric Adams revealed last week that the buildings with affected cooling towers included a Harlem hospital and a building housing a Whole Foods grocery store.

Air conditioning units are seen in the Harlem neighborhood amid a Legionnaires’ disease outbreak in New York City

Officials also said that while the number of infections is still rising, the rate of new reported cases each week since the outbreak has started to slow, suggesting the bacteria has been contained.

No information has been released about those who have died or been hospitalized.

Infected patients initially suffer a headache, muscle aches, and fever that may be 104 Fahrenheit (40 Celsius) or higher.

Dr Omer Awan, a medical professor at the University of Maryland with a specialization in epidemiology, told the Daily Mail: ‘Legionnaires’ disease can appear and present similar to the common flu but can be serious and result in pneumonia, or infection of the lung.

‘Patients with the disease can have high fever, cough, body aches, shortness of breath, nausea, vomiting and sometimes altered mental state.’

In serious cases, patients can develop severe pneumonia, and the bacteria can spread to the heart and blood, causing the potentially fatal complication sepsis.

Patients die from the disease due to lung failure, septic shock, a sudden severe drop in blood flow to vital organs, or acute kidney failure.

Legionnaires’ affects 8,000 to 10,000 Americans every year and kills about 1,000.

Cooling towers and air conditioning units are seen in the Harlem neighborhood amid a Legionnaires’ disease outbreak in New York City

The five ZIP codes affected in the outbreak are: 10027, 10030, 10035, 10037 and 10039.

Dr Micheal Genovese, chief medical advisor at AscendantNY in New York City, told the Daily Mail: ‘The high risk groups for Legionnaires’ disease include older adults (over 50) due to the natural immune decline that comes with age, people with a chronic lung condition due to the inability to effectively clear the bacteria from the lungs, smokers due to the damages to cilia in the lungs that normally sweep out bacteria and mucus, and individuals who are immunocompromised due to their weakened immune response.’

Doctors can treat the disease using antibiotics, but they warn that treatment is most effective in the early stages before the infection has spread in the body. Patients are often hospitalized.

In milder cases, patients may also suffer from Pontiac fever, a condition causing fever, chills, headache and muscle aches that occurs when the bacteria do not infect the lungs.

This condition goes away on its own without treatment and causes no further problems, doctors say.

Dr Genovese added: ‘Someone should seek medical attention if they experience any trouble breathing, chest pain, or mental confusion. Any high-risk individual who experiences any symptoms should seek medical attention immediately.’

And Dr Awan said, similarly: ‘If you live in NYC and have flu-like symptoms, you should seek medical attention immediately and go to an urgent care clinic or a hospital.

‘Early treatment with antibiotics is key, and evaluation at a healthcare facility will typically involve getting a chest x-ray and an urine or sputum test to confirm Legionnaires’ disease.’

The New York City outbreak was first revealed on July 22, when the health department reported eight cases.

It follows a previous outbreak in July 2015 in the Bronx, which became the second-largest Legionnaires’ disease outbreak in the US. Overall, a total of 155 patients were infected and 17 people died due to the disease from July to September that year.

The outbreak was eventually linked back to a cooling tower at the Opera House Hotel in the South Bronx, which had been contaminated with the bacteria and was releasing it in water vapor.

Dr Genovese told New Yorkers living near affected areas: ‘Be alert for symptoms and tell the medical provider about the outbreak so they can test for Legionella. Avoid standing directly in mists or sprays from cooling towers, A/C vents, decorative fountains, or outdoor water systems in the affected areas.

‘Avoid public hot tubs and spas. Don’t smoke and keep your immune system strong with adequate sleep, hydration, and nutrition.’

However, doctors also urged more action from city authorities.

Dr David Dyjack, executive director for the National Environmental Health Association, told the Daily Mail: ‘Individuals cannot completely eliminate the risk themselves. Prevention depends largely on building owners maintaining cooling towers and water systems.

‘What residents can do is be vigilant for symptoms and act quickly if they develop signs of illness.’