Had a positive result, or a notification about a guest?

If a laboratory result came back positive

1. Do not drain or shock the whole building blind. Find out which sample, which system and what count before you act, so you treat the right thing and can show what you did.
2. Isolate obviously affected equipment where you can (a spa pool, a single tower cell, a disused wing) without cutting water to occupied rooms.
3. Disinfect the affected system. Thai Department of Disease Control guidance is 50 mg/L free chlorine for at least one hour, or 20 mg/L for two hours, or thermal disinfection; cooling towers are shocked at 10 mg/L for three to six hours and cleaned.
4. Fix the cause, not only the count: the dosing point that failed, the tank that has not been cleaned, the heater set too low, the rooms that were not flushed.
5. Resample after disinfection, taken by someone other than the contractor who treats the water, at TEST TECH (ISO 11731:2017), IMC Thai (AS 3896:2017) or a Department of Medical Sciences Regional Medical Sciences Center (CDC-based method). Keep the chain of custody.
6. Record everything with dates, names and readings. That record is what turns a positive into a managed incident.

If you have been told a guest has Legionnaires' disease

Notifications reach Thai hotels in two ways: a Thai hospital reports a case, or a European case is reported to the ELDSNet surveillance network, which passes it through WHO to Thailand's Department of Disease Control. Officers from the Department or its regional office usually visit within days and sample the water themselves.

1. Cooperate fully, and tell the investigating officers what you plan to change before you disinfect or drain anything. To find the source they may want to take samples first, before any disinfection, so agree the order with them. Do not hold back any measure they or your contractor say is needed now to protect guests.
2. Gather your records now: the last assessment, chlorine and temperature logs, cleaning and disinfection dates, laboratory reports, the responsible person's training. The investigators ask for these, and so does your tour operator.
3. Tell your tour operator and brand before they hear it elsewhere. Two European cases linked to one hotel within two years count as a cluster, and operators are told about clusters even though hotel names are never published.
4. Expect two reports to Europe: a two-week report asking whether a site risk assessment has been carried out and a water management plan was in place, and a six-week report asking what was found, what was disinfected and whether a routine sampling and control system existed before the notification.
5. Disinfect and resample once the investigators have what they need, and have the corrective actions written up so that the six-week report shows a managed response.