Eighteen people have become ill in connection with the outbreak, according to officials. All of the reported cases are associated with the Santa Clara facility.
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Legionella infections occur when individuals breathe in mist from a contaminated water source. The infection can lead to severe pneumonia.
Kaiser officials said the hospital completed treatment of its water system on Monday. The health care provider said its facilities are operating normally.
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The Santa Clara County Health Department said the risk to the broader community is low.