A Hidden Cause of Pneumonia? Underdiagnosis of Legionellosis is a Cause for Concern in India
Year: 2025
Type: article
Abstract: Legionnaires’ disease, a severe form of pneumonia caused by the Legionella bacteria, has emerged as a significant public health concern in India. Despite its discovery in 1976 (after an outbreak of pneumonia among the participants of the American Legion Conference held in Philadelphia, USA), the disease remains underreported and often misdiagnosed in many countries, including India.[1] Legionella bacteria are ubiquitous in aquatic environments, both natural and artificial. These bacteria can colonize various water sources, including rivers, lakes, and man-made systems such as air conditioning units, cooling towers, and showerheads. As noted by the World Health Organization (WHO), “Legionella bacteria can be found naturally in lakes, streams, and soil, but it can also contaminate drinking water and air systems, especially in large buildings” – WHO, 2023. The transmission of Legionella to humans occurs through inhalation of contaminated aerosols.[2] The clinical presentation of Legionnaires’ disease can be varied, making it challenging to differentiate it from other forms of pneumonia. The common symptoms include fever, cough, shortness of breath, muscle aches, and headache. In severe cases, patients may experience confusion, hallucinations, and other neurological symptoms.[3] The diagnosis of Legionnaires’ disease relies on a combination of clinical findings, laboratory tests, and imaging studies. While chest X-rays may reveal pneumonia-like infiltrates, they are not specific for Legionella infection.[4] Blood tests can help to identify elevated inflammatory markers but are not diagnostic. The gold standard for diagnosing Legionnaires’ disease is the detection of Legionella bacteria in the clinical specimens. This can be achieved through culture-based methods or molecular techniques, such as polymerase chain reaction (PCR). However, culture-based methods are time-consuming and require specialized laboratory techniques. PCR, on the other hand, is a rapid and sensitive method for detecting Legionella DNA in the respiratory samples. Another valuable diagnostic tool is the urine antigen test (UAT). This test detects Legionella antigens in urine and can be a rapid and noninvasive method for diagnosing Legionnaires’ disease. However, UATs primarily target Legionellapneumophila serogroup 1, the most common cause of the infection. Other Legionella species (such as serogroups) may not be detected by this test.[3] Despite the availability of diagnostic tests, Legionnaires’ disease remains underdiagnosed in many settings. Several factors contribute to this underdiagnosis, including a lack of awareness among healthcare providers, limited access to specialized diagnostic laboratories, and delayed testing. In addition, the nonspecific nature of the clinical presentation and the challenges associated with culturing Legionella bacteria can further complicate the diagnosis.[5] A recent study by Sreenath et al. (2020) highlights the underdiagnosis of Legionnaires’ disease in India. The study, conducted at a referral hospital in New Delhi, found that Legionella spp. was identified in 2.3% of patients with pneumoniae.[1] This finding underscores the need for increased awareness and improved diagnostic capabilities to accurately identify and treat Legionnaires’ disease in India. To improve the diagnosis and management of Legionnaires’ disease, several strategies can be implemented. First, healthcare providers should be aware of the clinical features and risk factors for Legionnaires’ disease. Early recognition of the disease is crucial for the timely initiation of appropriate antimicrobial therapy. Second, diagnostic laboratories should have the capacity to perform culture-based and molecular tests for Legionella. Third, public health authorities should implement surveillance systems to monitor the incidence of Legionnaires’ disease and identify outbreaks.[6] As a part of the community surveillance, there should be regular monitoring of public water systems, especially cooling towers, and fountains to identify the potential sources of Legionella contamination. There should be prompt investigation of suspected outbreaks of pneumonia, particularly those with a cluster of cases. Regular testing of water samples from hospital water systems, including those used for drinking, bathing, and medical procedures to identify potential contamination would be done as a part of hospital surveillance programs. Hospitals should implement surveillance systems to identify the cases of pneumonia particularly those with atypical features. Adherence to strict infection control practices, including proper disinfection of medical equipment and surfaces, can prevent the spread of Legionella in the healthcare settings. Proper treatment of water used in cooling towers, hot water systems, and other water systems, maintenance, and cleaning of ventilation systems and water systems, especially in healthcare facilities can reduce the risk of airborne transmission of Legionella.[7] Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
Authors: Diganta Banerjee, Rajashri Patil, Preethy Edavaloth, Shahzad Mirza
Language: English
Subfield: Endocrinology
Domain: Life Sciences
Open Access status: hybrid
OpenAlex ID: W4411713688