L. pneumophila serogroup 1 (Lp1) is the leading cause of LD, accounting for up to 92% of clinically recognized legionellosis infections in the US and Europe1. Although Lp1 predominates as the cause of LD, it is not found at disproportionately higher rates in the environment than the 16 other Lp serogroups. L. bozemanii serogroups 1 and 2, L. dumoffii, and L. micdadei, account for most of the remaining human infections67. Other species of Legionellae rarely cause disease except for L. longbeachae where high rates of infection and disease have been reported in Australia and New Zealand8. According to the Centers for Disease Control and Prevention (CDC), the number of cases reported rose 217% while the incidence rate of legionellosis in the US increased almost 200% between 2000 and 20099. In 2015, there were 15 outbreaks in the US and Europe with a 10% case fatality rate in addition to the growing number of cases caused by non- Lp species. There is also a recent report of probable person-to-person transmission10. These collective findings drive home the critical need to better characterize legionellae to improve our understanding of their biology and epidemiology to advance the design of strategic interventions.