A large outbreak of Legionnaires’ Disease in an industrial town in Portugal

• Autor(a) principal: George, Francisco
• Data de Publicação: 2016
• Outros Autores: Shivaji, Tara, Pinto, Catia Sousa, Serra, Luis Antonio Oliveira, Valente, João, Albuquerque, Maria João, Vicêncio, Paula Cristina Olivença, San-Bento, Ana, Diegues, Paulo, Nogueira, Paulo Jorge, Marques, Teresa, Rebelo, Helena, Costa, Filipa, Rodrigues, Raquel, Nunes, Alexandra, Borges, Vitor, Gomes, João Paulo, Sampaio, Daniel, Barreiro, Paula, Duarte, Silvia, Carpinteiro, Dina, Mendonça, Joana, Silva, Catarina, Vieira, Luís, Simões, Maria Joao, Gonçalves, Paulo, Nunes, Baltazar, Dias, Carlos, Machado, Jorge, Almeida, Fernando, Goncalves, Elsa A., Carvalho, Lucilia, Viterbo, Pedro, Jardim, Dilia, Lacasta, Nuno, Boavida, Filomena, Perez, Ana, Santana, Isabel, Matias, Paula, Banza, Nuno, Rabacal, Carlos
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/108126
• topic: Legionnaires’ disease; Legionella pneumophila fraseri; Doença dos Legionários

ABSTRACT - Background: We describe the investigation and control of an outbreak of Legionnaires’ disease in Portugal in October, November and December 2014. Methods: Confirmed cases were individuals with pneumonia, laboratory evidence of Legionella pneumophila serogroup 1 and exposure, by residence, occupational or leisure to the affected municipalities. 49 possible sources were reduced to four potential sources, all industries with wet cooling system, following risk assessment. We geo-referenced cases’ residences and the location of cooling towers defining four study areas 10 km buffer centered on each cooling tower system. We compared the number of cases with expected numbers, calculated from the outbreak’s attack rates applied to 2011 census population. Using Stones’ Test, we tested observed to expected ratios for decline in risk, with distance up to 10 km four directions. Isolates of Legionella pneumophila were compared using molecular methods. Results: We identified 403 cases, 377 of which were confirmed, 14 patients died. Patients became ill between 14 October and 2 December. A NE wind and thermal inversion were recorded during the estimated period of exposure. Disease risk was highest in people living south west from all of the industries identified and decreased with distance (p < 0.001). 71 clinical isolates demonstrated an identical SBT profile to an isolate from a cooling tower. Whole genome sequencing identified an unusual L. pneumophila subsp. fraseri serogroup 1 as the outbreak causative strain, and confirmed isolates’ relatedness. Conclusions: Industrial wet cooling systems, bacteria with enhanced survival characteristics and a combination of climatic conditions contributed to the second largest outbreak of Legionnaires’ disease recorded internationally.