Airflow dinamics models support the hypothesis of the hydrotherapy pool as the source of infection in a travel-associated outbreak of legionnaires
By Crespi, S.; Bettencourt, J.H.; Lopez, C.; Hernandez-Garcia, E.
Poster presented by Sebastia Crespi at the 8th International Conference on Legionella (Melbourne, Australia), 29 October, 1 November 2013
AIRFLOW DINAMICS MODELS SUPPORT THE HYPOTHESIS OF THE HYDROTHERAPY POOL AS THE SOURCE OF INFECTION IN A TRAVEL-ASSOCIATED OUTBREAK OF LEGIONNAIRES’ DISEASE
Sebastian CRESPI 1, João BETTENCOURT 2, Cristobal LÓPEZ 2 and Emilio HERNÁNDEZ-GARCÍA 2
1 Policlinica Miramar, Clinical Laboratory, Palma, Spain;
2 IFISC (Instituto de Física Interdisciplinar y Sistemas Complejos), Consejo Superior de Investigaciones Científicas and Universidad de las Islas Baleares, Palma, Spain.
Forty-three cases of Legionnaires’ disease were associated to a hotel in Calpe, Spain, from November 2011 till June 2012. The initial epidemiological data suggested that the hydrotherapy pool, located in the Spa area at the hotel basement, was not involved and the outbreak was attributed to the domestic water system. In February 2012, the infecting strain was isolated from the hydrotherapy pool and the hypothesis of the pool as the possible source of infection was generated. Airflow dynamics models were developed to test if aerosols from the pool could reach the hotel lobby through a glass cupola over the spa’s ceiling.
A simplified 2D model of the spa was considered in this approach. The FLUENT 12 software was used in the modeling and solution phases. The model domain was meshed with ANSYS Workbench 12. The model geometric properties were based on actual data obtained from the hotel.
The model showed that the temperature gradient between the pool water and ambient air is capable of producing an upward air plume with a maximum velocity of 1.5 cm/s. The steady-state mean-flow vectors show two circulation cells moving air from the bottom upwards through the center of the cupola. The aerosols produced at or near the pool surface can be carried upwards and could pass easily to the lobby area through the glass cupola. Efforts at prevention and control in hotels must take into consideration the potential for Legionella spreading from possible sources that are in low- or even non-visited areas.
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