Introduction:
Cruise ship mainly conduct syndromic surveillance for gastrointestinal illness (GI) and Influenza Like Illness (ILI). The COVID-19 and other pandemics demonstrated the need a more inclusive systematic approach in syndromic surveillance for known and unknown diseases. Healthy sailing under task 4.1 developed a new syndromic surveillance system for large passenger ships.

Methods:
A search was conducted in PubMed and grey literature in order to identify existing syndromic surveillance practices followed on ships and other settings (e.g. mass gathering events, touristic venues, migrants’ campuses, etc.)^1-7. The HEALTHY SAILING epi-team consisting of epidemiologists from three different institutions decided on the surveillance objectives, and then defined the syndromes, case definitions, indicators and the thresholds, considering literature review results and expert opinion. A set of standardised recording forms were created and the system was pilot tested by analysis of historical data and by acquiring feedback of the actual forms from ship doctors.

Results:
The new surveillance system consists of three syndrome categories: respiratory illness (including ILI, Acute Respiratory Illness-ARI and pneumonia), gastrointestinal Illness (including bloody diarrhoea and acute gastroenteritis) and other syndromes (including additional eight syndromes). A medical log, a surveillance log and 11 additional forms for recording the measures applied to patients and to the environment were developed. Results from pilot testing revealed the following:

• need for standardisation of what is considered “unusual” for each individual,

• training on the use of ICD coding system,

• clear recording of infectious acute and chronic gastroenteritis cases,

• doctors’ notes in the medical logs should be more detailed,

• syndromic surveillance should be supplemented by laboratory testing

Conclusions:
Incorporation of the new syndromic surveillance system into the HEALTHY SAILING E-SS prototype and implementation by large passenger ships is expected to improve case detection and enable early warnings for outbreaks⁸.