Legionellosis Case Study

II. THEORETICAL BACKGROUND

2.1 Review of Related Literature

Acute Lower Respiratory Tract Infection and Pneumonia in the Philippines

Among the developing countries, infectious diseases are still one of the main public health concerns. Here in the Philippines, the Acute Lower Respiratory Tract Infection and Pneumonia is the second leading cause of morbidity (2012) and third leading cause of mortality (1998) in Filipinos, based on the Philippine Health Statistics Report from the Department of Health (FHSIS 2012; FHSIS 1998).

Pneumonia is defined as an infection of the lungs and is characterized mainly by inflammation of the alveoli in the lungs (www.mayoclinic.org). It can be caused by several kinds of organisms and some of these typical bacterial

Legionellosis

Legionellosis is the term used to the diseases caused by Legionella pneumophila, and related Legionella bacteria that are found in aquatic environments, and other warm damp places such as cooling towers (Fields et al., 2002). It is an infection that results from inhaling airborne water droplets or mist containing viable L. pneumophila, which are small enough to pass deep into the lungs and be deposited in the alveoli, the small pockets in the lungs. But the dose of L. pneumophila required to infect humans is not definitively known (WHO, 2007).

The severity of legionellosis varies from mild febrile illness (Pontiac fever) to a potentially fatal form of pneumonia (Legionnaires’ disease) that can affect anyone (Fields et al., 2002). And cases of legionellosis can be grouped by the way they are acquired, i.e. in the community, in the health-care setting (nosocomial), and travel associated as stated in the categorization by the World Health Organization

In nosocomial outbreaks, the average mortality has been reported to be about 15–20% of hospitalized cases (Guerin, 1992; Roig & Rello, 2003) and up to 40% case-fatality rate was recorded amongst nosocomial infections of legionellosis (O’Mahony et al., 1990; CDC,1997). Cases of legionellosis have been recorded in many countries in the world. The proportion of hospital-acquired pneumonia due to Legionella has been reported as ranging from 0 to 47% (Hutchinson, 1990). In the United States, between 8,000-18,000 cases of Legionnaires’ disease occur annually and 25% of cases are hospital acquired (Marston et al., 1994; Kool et al., 1999). Infection with Legionella spp. ranks among the three most common causes of severe pneumonia and is isolated in 1-40% of cases of hospital-acquired pneumonia (Deideren, 2008).

However, in the Philippines, Legionnaires’ disease is rarely diagnose, and more so with the diagnosis of nosocomial pneumonia caused by Legionella spp. Unfortunately, literature search showed scarcity of data regarding the prevalence of Legionella species and its serogroup in water environment, as well as reported confirmed cases of legionellosis. Furthermore, the presence of this organism in the hospital water system which could be a potential source of nosocomial Legionnaires’