On Monday, September 2, 2024, healthcare professionals reported several cases of gastrointestinal symptoms among residents of Saint-Didier-en-Velay and La Séauve-sur-Semène to the Haute-Loire Prefecture and the Auvergne-Rhône-Alpes Regional Health Agency. To better understand the scope of this outbreak and investigate its cause, Santé publique France, in collaboration with the Auvergne-Rhône-Alpes Regional Health Agency and the Haute-Loire Prefecture, conducted an online survey of residents in these two municipalities.

The online survey was distributed by local representatives starting Tuesday, September 3, and remained accessible until Tuesday, September 10. Anyone residing in Saint-Didier-en-Velay or La Séauve-sur-Semène (whether sick or not) was invited to complete the questionnaire.

An online survey that yielded over 900 responses

The online survey collected more than 900 responses. Analysis of the questionnaires completed by residents of Saint-Didier-en-Velay or La Séauve-sur-Semène shows a high number of people (656, or 13% of the residents of the two municipalities) reporting symptoms characteristic of gastroenteritis (abdominal pain, nausea, diarrhea, vomiting, and fever for some of them), mostly resolving within 24 hours.

The symptoms occurred mainly during the last weekend of August (Saturday, August 31, and Sunday, September 1).

Results supporting the hypothesis of a one-time contamination of the water system, which is now compliant

The questionnaire asked about the consumption of tap water for drinking.
It appears that people who reported drinking tap water (occasionally or exclusively) had a higher risk of becoming ill than those who reported not drinking tap water.

In addition, 191 people (including 145 who fell ill) reported noticing a problem with the quality of the distributed water (abnormal color, taste, or odor) during the month of August, and most during the last week of August.

The large number of ill individuals whose only exposure was the consumption of tap water in the municipalities of Saint-Didier-en-Velay and La Séauve-sur-Semène points to the hypothesis of contamination of the water supply system in these two municipalities.

The distribution of cases across the entire territory of these two municipalities supports this hypothesis.

The rapid decline in the number of cases beginning Monday, September 2, suggests that contamination likely occurred as a one-time event during the last days of August.

Investigations are underway by state agencies to identify the cause of this contamination and to take all necessary measures to prevent a potential recurrence.

Tap water compliant according to the latest test results and an investigation into the source of the contamination

All analyses conducted by the operator on the tap water system show, to date, compliant results. Therefore, the water is safe to drink.

At the same time, biological analyses are underway and should help identify the germ or germs responsible for this outbreak.

To limit the spread of the disease, the ARS recommends following certain hygiene guidelines

Whether of viral or bacterial origin, the bacteria in question are likely to cause secondary cases of gastroenteritis through person-to-person transmission.

Therefore, the ARS recommends following these hygiene measures:

• People who are sick should avoid group activities and common areas as long as they show signs of gastroenteritis.

• Sick individuals and those around them must maintain strict personal hygiene:

  • Systematically wash hands with soap and water after using the restroom, before preparing meals, and before eating. Dry hands with single-use paper towels.

  • Dispose of paper towels in a trash can with a lid.

  • For hand hygiene, an alcohol-based hand sanitizer may be used. However, if hands are visibly soiled, these solutions lose their effectiveness and must be preceded by washing with soap and water.

• In addition, you should:

  • Prohibit the sharing of water bottles or glasses.

  • Use individual toiletries (toothbrushes, towels, gloves, etc.).

Government agencies (Prefecture, DDT, and ARS) continue to closely monitor the situation, in coordination with the mayors concerned and the Loire Semène Community of Municipalities.

Furthermore, the Loire Semène Community of Municipalities has signed a resilience agreement with the Loire-Bretagne Water Agency.
As part of this, an interconnection project is underway with the Lherbret water treatment plant to further strengthen the supply of drinking water, with completion expected in approximately six months.