At least 100 people fell ill in Greece recently with contaminated water suspected as the source.

The Hellenic National Public Health Organization (EODY) said an increased incidence of gastroenteritis cases was observed in late May in residents of the areas of Rizomylos and Stefanovikiou, Magnesia.

A total of 100 cases, of all ages and both sexes, with symptom onset dates between May 24 and June 2, were reported. Nine children were hospitalized, as well as an elderly person with underlying conditions.

Samples from the water supply network were taken and laboratory analysis revealed Salmonella, in addition to microbial indicators of fecal contamination.

Six stool samples from hospitalized children were positive for Salmonella, as was another sample taken from a different patient.

Officials issued a notice to the public advising them not to drink water from the supply network or to use it to wash food and in food preparation. If it has to be used, it should be boiled at 100 degrees C (212 degrees F) for at least three minutes. Sanitation of the water supply network was started and daily checks were conducted until the water quality was restored.

Previous incidents
It is not the first waterborne outbreak in Greece. According to EODY surveillance data, 35 outbreaks with 6,128 cases and 218 hospitalizations were identified between 2004 and 2023. Seven outbreaks with more than 200 cases were recorded and the largest affected 1,640 people.

In August 2022, the Hellenic National Public Health Organization was notified about a gastroenteritis outbreak in Southern Greece. At least 33 people fell sick and seven were hospitalized. Tap water consumption was the only significant risk factor for illness. Salmonella Bovismorbificans was isolated from eight stool and one tap water samples. An investigation did not reveal the way water might have been contaminated.

A study, published in the International Journal of Environmental Research and Public Health, found residual chlorine levels were lower than the minimum value required by Greek legislation, before and during the outbreak. This may suggest deficiencies in water sanitation practices, said scientists.

Another study said that delays in reporting and the methods of investigations show that surveillance of waterborne outbreaks and response methods should be strengthened, and operational procedures should be standardized.

Listeria warning
EODY has also warned about an increase in Listeria infections in 2023 and 2024.

Listeriosis surveillance through the Mandatory Disease Reporting System began in Greece in 2004. Between 2004 and 2023, 266 cases and 59 deaths were reported.

In 2023, 31 cases were recorded. The median age of patients was 67 with a range from less than 1 to 92 years old and 18 were men. From January to mid-April 2024, 12 infections had been reported.

To protect public health, EODY said it is taking a range of measures including advising health units across the country about procedures to be followed when cases are detected. The Hellenic Food Authority (EFET), Ministry of Rural Development and Food, and National Reference Laboratory for Listeria monocytogenes in food have been informed.

Patient samples have been sent to a lab collaborating with ECDC for whole genome sequencing, with the aim of identifying possible outbreaks as well as any connection with global incidents. A working group has also been established to exchange data in the event of an outbreak and to discuss actions to respond to the issue.