Case Study 1
A 64-year old male with fever, malaise, and cough.
Question 5 of 6
What is the most likely source of Legionella pneumophila?
Exposure to water containing Legionella pneumophila
Patients are usually infected by inhalation of
contaminated water. The concentration of Legionella usually has to exceed 1000
/milliliter to be infectious. Typical sources of contaminated water include cooling
systems, shower heads, potable or domestic water systems, respiratory therapy
devices, industrial coolants, and whirlpool spas.
Contact with another infected person
Humans are dead end hosts. Legionellosis is infectious for humans but not
transmissible from person to person.
Exposure to an infected animal
Lower animals are rarely affected by exposure to Legionella pneumophila and
are an unlikely source of infection. Also, the patient reported no contact with
The Biology Project
University of Arizona
Tuesday, August 4, 1998
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