The number of Legionnaires’ disease cases has increased from 19 to 24, and the death toll has risen from 1 to 2, the New York City health department said on June 1st, 2022. Four people are currently hospitalized with the disease, the city health department officials also confirmed on 06/01/22. The outbreak has permeated the Highbridge section of the Bronx since May 3, 2022. The 2 individuals who died from the illness were more than 50 years old and had risk factors for severe disease, according to health officials. The bacterium that causes the disease, Legionella pneumophila, was found in 4 cooling towers in the Bronx. The towers were completely remediated, according to the health department.
People get Legionnaires’ disease – a type of pneumonia – by breathing in water vapor with Legionella bacteria, which grows in warm water, such as cooling towers, whirlpool spas, hot tubs, humidifiers, hot water tanks and evaporative condensers of large air-conditioning systems, according to the health department. Personal home and car air-conditioning units are not a risk because they do not use water to cool the air, according to the Centers for Disease Control and Prevention (CDC) website.
A 2016 CDC factsheet lists drinking water as a source of infection, both through showering, and in rare cases, breathing in the bacteria when water “goes down the wrong pipe” and enters the lungs. The federal agency website says that this is particularly relevant for people with swallowing difficulties – indicating that the bacterium is ASPIRATED after colonization of the nasopharynx. This assumption differs from the city health department messaging, which says individuals “only” get sick by “breathing in” water vapor with the bacteria (i.e., bacteria are directly inhaled into the ALVEOLI). It is highly unlikely someone would get infected by consuming the bacteria from NYC’s water, as the city’s water is treated. She expects cases to halt now that the infected cooling towers have been thoroughly cleaned and inspected.
Eradication of these bacteria from plumbing systems is often difficult. Long-term persistence within these water systems is favored by the intracellular location of Legionella within several species of protozoa, where Legionella replicate and which provide protection from environmental stressors, like biocides and heat treatment; the formation of biofilms allows adherence of Legionella to the inner surfaces of the plumbing systems. L. pneumophila have been shown to persist for long periods in biofilms in a viable but nonculturable (VBNC) state after exposure to a biocide or heat (>60°C) treatment.
Symptoms of the disease resemble other types of pneumonia, such as fever, chills, muscle aches and cough. Most people exposed to the bacteria do not get sick. As for those who do get sick, the CDC says most end up needing hospital care and make a full recovery, but 1 in 10 people who get the disease die from the infection. People 50 years of age and older, cigarette smokers and people with chronic lung disease or compromised immune systems (T-cell defect) are at higher risk, for whom the disease can be severe or even fatal, according to the NYC health department. The disease is not contagious, and when caught early, it can be treated with antibiotics, according to the city health department.
The number of Legionnaires’ cases has been on the rise over the past 2 decades, according to the CDC. In 2018, health departments reported nearly 10,000 cases in the United States. But the disease is likely underdiagnosed, and the true number of cases may be 1.8–2.7 times higher than reported. While Legionnaires’ cases can occur any time, it is more prevalent in the summer and early fall, the CDC says.
By Dr. Simone Müschenborn-Koglin Contributing Editor, GHP