A Legionnaires' disease cluster in New York has left two people dead and sickened over 50 others. Here's what California residents should know.

Legionnaires' disease is caused by Legionella, a bacteria that can travel through water systems and devices. Although most healthy people don't contract it, it can be deadly for those who do.

Two people have died and at least 58 people have been diagnosed with Legionnaires’ disease in a cluster that broke out in New York City last week.