An unusually long-lasting outbreak of community-acquired Legionnaires' disease, 2005–2008, Italy

Abstract

An unusually long-lasting community-acquired outbreak of Legionnaires' disease (LD) occurred in the inhabitants of a town in northern Italy from 2005 to 2008. Overall, 43 cases were diagnosed including five deaths. Hundreds of water samples were collected for Legionella isolation but only two clinical samples were obtained. Clinical strains were ST23 as were environmental isolates detected in most Legionella-positive patients' homes and those from a public fountain. Although no Legionella was found in the municipal water mains, a continuous chlorination was applied in 2008. This action resulted in a halving of cases, although incidence remained tenfold higher than the Italian average incidence until the end of 2013, when it dropped to the expected rate. Retrospective analyses of prevalent wind direction suggested that a hidden cooling tower could have been the main cause of this uncommon outbreak, highlighting the importance of implementation of cooling tower registers in supporting LD investigations.

Performance of Legiolert Test vs. ISO 11731 to Confirm Legionella pneumophila Contamination in Potable Water Samples

“…When Legionella colonizes the water systems, it often finds favorable conditions for growth, such as temperatures between 25 °C and 45 °C or the presence of biofilm, reaching high concentrations and becoming a serious risk for human health. After the first LD outbreak occurred in Philadelphia in 1976, numerous other outbreaks and sporadic cases have been reported worldwide [ 4 , 5 , 6 , 7 , 8 , 9 , 10 ]. In Italy in 2018, the incidence of Legionnaires’ disease was 4.9 cases per million inhabitants, 2964 notified cases [ 11 ], and in the European network for Legionnaires’ disease surveillance, Italy ranked first in terms of the number of reported cases [ 12 ].…”

Legionnaires’ Disease: Clinicoradiological Comparison of Sporadic Versus Outbreak Cases

“…In most cases, water cooling or air-conditioning systems directly contributed to transmission of the disease, 6 whereas fountain water and portable water systems in hotels have also been implicated in a few cases. 7,8 Incidence of Legionnaires’ disease in New York City increased by 230% from 2002 to 2009, and the outbreak in summer of 2015 involved 120 patients, resulted in 12 deaths, and carried a 10.6% fatality rate. 6 The outbreak was centered in the South Bronx, the poorest urban country in United States, which is already struggling with a very high prevalence of asthma and diabetes mellitus.…”

Author Response to Comments on “Rolling epidemic of Legionnaires’ disease outbreaks in small geographic areas”

“…Regarding contamination of multiple cooling towers, the majority of publicly reported LD outbreaks are due to single-cooling towers, and fewer are associated with multiple towers. The largest number of towers we identified in previous published outbreaks is seven 12 , but most cases that involved multiple contaminated towers reported fewer towers than seven, often only involving two towers 13,14 . In this context, the reported number of contaminated towers in the Bronx outbreak appears unusual.…”