Probable Person-to-Person Transmission of Legionnaires’ Disease

Legionnaires’ disease is an often severe form of pneumonia typically acquired by susceptible persons (e.g., elderly persons and smokers) through inhalation of aerosols that contain legionella species. A cluster of cases of this disease occurred in Vila Franca de Xira, Portugal (2014). One of the first cases of disease occurred in a 48-year-old man (Patient 1), a smoker, who had been employed since October 6, 2014, as a maintenance worker at an industrial cooling tower complex in Vila Franca de Xira that was subsequently found to be contaminated with Legionella pneumophila. His symptoms began on October 14, and on October 19, he had severe respiratory symptoms, including an intense cough. During that night, his mother (Patient 2) took care of him until he was admitted to the hospital (Centro Hospitalar do Porto) about 8 hours later. On October 22, he was transferred to another hospital to receive extracorporeal membrane oxygenation. On October 27, Patient 2, who was a previously healthy 74-year-old woman, began to report fever, cough, and loss of appetite. She was admitted to the same hospital on November 3 with septic shock due to pneumonia, and she died on December 1. Patient 1 died on January 7, 2015. Urine specimens obtained from both patients showed positive results on testing for legionella antigens with the use of a commercial enzyme immunoassay (Binax), and legionella was grown in culture from respiratory secretions. L. pneumophila serogroup 1 was identified, and strains were sent to the National Institute of Health in Lisbon for sequence-based typing and whole-genome sequencing. Patients 1 and 2 lived alone in Porto, and their house consisted of small nonventilated rooms without air-conditioning units or room humidifiers. Collected water samples from the bathroom and the kitchen and a swab of the shower drain were negative for legionella. Patient 1 did not take water from Vila Franca de Xira to Porto. {Ref: N England J. of Medicine p. 374:497-498]