Ana M. Correia and colleagues (N Engl J Med 374;5 February 4, 2016) present a convincing case of person-to-person transmission of Legionnaires’ disease between son and mother. Seen the epidemiology of the two cases and the results of whole-genome sequencing, the only part of the short report I do not understand is the “probable” in the title. I wouldn’t know what else to include in order to call it “proven”.
Consequently, the question is whether this “new” transmission route has implication for infection control in the hospital setting. The mother had very close contact over an extended amount of hours with her severely coughing son, in a small and badly ventilated room. In opposite to HCWs who in this situation generally would wear a mask, she obviously used no personal protective equipment. Finally, while described as formerly healthy, no further details are given about the conditions possibly increasing the susceptibility of the 74-year old to Legionella.
Thus, while person-of-person transmission seems proven in the present case, I believe that the circumstances are unique and don’t require to change the present infection control measures taken in patients with Legionnaires disease.