2005 - Legionellosis

Table 1. Legionellosis Cases by Race and Sex, Indiana, 2005

  2005 2001-2005
Cases Rate* Cases
Total 33 0.53 167
   White 21 0.38 126
   Black 7 1.26 20
   Other 0 0 0
   Not Reported 5 - 21
   Male 20 0.65 102
   Female 13 0.41 65
   Not Reported 0 - 0
*Rate per 100,000 population based on the U.S. Census Bureau’s population data as of July 1, 2005

Legionellosis is a respiratory infection caused by Legionella bacteria, most commonly Legionella pneumophila. These bacteria are transmitted by inhalation of contaminated water aerosols. People over 50 years of age, especially those with a history of smoking and weakened immune system, are at the greatest risk of acquiring infection. The severe form of legionellosis, commonly known as “Legionnaires’ Disease”, is characterized by pneumonia, fever, and myalgia. A milder, self-limiting form of the illness, known as Pontiac Fever, is characterized by fever, cough, and myalgia. Neither infection is transmissible person to person. Legionellosis can occur as individual sporadic cases or as an outbreak related to a point-source exposure.

There were 33 cases of legionellosis reported in Indiana in 2005, for a rate of less than 1 case per 100,000 population (Table 1). Figure 1 shows the number of reported cases of legionellosis for 2001-2005. The number of reported cases increased during the late summer and early fall months (Figure 2). The impact of Legionella infections was most notable when comparing cases by age group. The age group with the highest incidence rate was in persons aged 60-69 years (1.63), followed by those aged 50-59 years (1.27) (Figure 3).

Legionellosis occurred throughout Indiana in 2005; however, only two counties, Lake (1.2) and Marion (0.6), reported five or more cases (Figure 4). No outbreaks of legionellosis occurred in Indiana in 2005.

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