Epidemiological characteristics related to Legionnaires Disease in Thailand, 2013–2024

Abstract

Legionnaires' disease is a serious public health concern, as most cases occur among foreign tourists, which can impact the country’s image. The aim of this study is to describe the epidemiological characteristics of Legionnaires' disease in Thailand using secondary data collected from all reported cases through the Event-Based Surveillance system of the Department of Disease Control between January 1, 2013, and September 30, 2024. Descriptive statistics were used to analyze the data. Findings revealed that from 2013 to 2024, there were 229 reported cases of Legionnaires' disease, with 5 deaths, resulting in a case fatality rate of 2.18%. The most affected age group was 45–64 years (49.25%), with a median age of 62 years. Among foreign tourists diagnosed in their home countries after returning from Thailand, the largest proportion was from the United Kingdom, followed by Sweden, Germany, the Netherlands, and Denmark. The patients reported traveling to major tourist provinces of Thailand, including Phuket, Surat Thani, Krabi, Bangkok, and Chonburi. In terms of environmental sampling, the highest detection of Legionella spp. was found in shower water (35.94%), followed by swabs from the shower (35.00%) and water from taps or sinks (23.81%). 85.71% of the accommodations had a hot water system lower than 50°C or a residual free chlorine level of less than 0.02 ppm. Therefore, to reduce the risk of Legionnaires' disease infection, awareness of its prevention should be raised among operators and relevant personnel. Additionally, the intensity of disease surveillance should be increased during peak travel periods, along with public awareness campaigns to inform tourists and the public about preventing Legionella spp. infection.