Legionnaires’ diseases in travelers: Environmental outbreak investigation in the hotel located in Bangkok, January 2023

Abstract

Background: Thailand’s Department of Disease Control was informed that a Swedish traveler was sick with
Legionnaires’ disease after traveling to Thailand. This could impact the Thai Tourist Section and economy due to
the health threats from the disease, which might result in the alert system of those tourists’ countries warning
their people not to travel to Thailand. This environmental outbreak investigation aims to identify any presence
of Legionella spp. in the hotel environment where the traveler had stayed, provide advice to the establishment
on how to prevent the spread of disease in the water system, coolant, and cooling tower, and determine whether
the traveler's infection was related to the hotel's water supply.
Methods: The traveler’s diagnosis had been confirmed by the history of his signs and symptoms of Legionnaires’
disease with the laboratory result. We also explored general information about the hotel and investigated the
risk environment, which was the water system, coolant, and cooling tower. Some water sources were sent to
investigate Legionella spp. Finally, we try to find out whether this traveler got the infection from the hotel’s
environment.
Results: The traveler had Legionnaires’ disease. Although the hotel hired an outsource company to investigate
and report the water quality every 6 months, there were water sources that did not meet the standard to control
the disease, such as inadequate free residual chlorine, and Legionella spp. was also found in the water system of
this hotel at 5,000 CFU/L. (European’s standard less than 1,000 CFU/L). This traveler may get Legionella spp.
infection from the hotel.
Discussions and Conclusion: The onset of Legionnaires’ disease was 2–14 days, and the onset of this traveler
occurred 1–3 days after the exposure. Therefore, the traveler could be infected by the water system of this hotel.