Environmental and structural impacts of the 2023 Daniel storm and subsequent floods in the Thessaly Region (Central Greece) and factors controlling infectious disease emergence in flooded areas

In early September 2023, the Thessaly Region (central Greece) was devastated by the Daniel storm, which brought extreme precipitation. The resulting embankment failures in the Pineios catchment caused flooding up to 4 m deep, submerging many rural areas for days. This event claimed 17 lives and caused extensive damage to structures and infrastructure, including roads, bridges, lifelines, residences, agricultural land, livestock facilities, industrial and tourist infrastructure.

The above weather conditions in the Region of Thessaly, the subsequent floods and their impacts had the potential to affect public health and in particular to cause sporadic cases, outbreaks and epidemics of infectious diseases in the affected area, as has been shown by similar examples of floods and other hydro-meteorological hazards, not only in developing, but also in developed countries worldwide.

The aim of this research is to highlight all the risk factors that favor the occurrence of infectious diseases in the area affected by the Daniel storm and the subsequent flooding. This is achieved not only by taking into account the significant results of the existing relevant research on the effects of hydrometeorological events in the affected areas, but also by mainly presenting field data obtained from field surveys during and after the event.

Adverse conditions from these extreme events fostered public health risks contributing to incidence increase of rodent- and water-borne diseases, and respiratory infections.

From September 5 to December 31, 2023, 296 patients from the affected areas were evaluated for suspected leptospirosis at Thessaly hospitals, with 45 cases (15.3%) confirmed, according to the newsletters of the National Public Health Organization on May 30, 2024.

Damage to water supply and irrigation systems in Thessaly led to shortage of clean water after the storm. Clusters of gastroenteritis cases were reported in affected areas, alongside increased respiratory infections due to influenza virus and SARS-CoV-2.

Receding floodwaters can create mosquito breeding grounds, increasing the risk of mosquito-borne disease emergence. However, heavy rainfall and flooding may reduce mosquito density by diluting organic matter and washing away habitats. Combined with colder weather and preventive measures against mosquitoes, no West Nile virus cases were reported in Thessaly after mid-October.

A high injury rate during disasters and low tetanus vaccination coverage can lead to outbreaks. However, Greece's successful national vaccination program and prompt vaccination of individuals with uncertain or incomplete immunization status in flood-affected areas prevented any tetanus cases or outbreaks.

The conditions that emerged resulted in the mobilization of the Civil Protection and Public Health authorities not only to deal with the impact of the storm and the subsequent flooding, but also to prevent and manage indirect public health impacts. The instructions and guidelines to affected residents, health professionals and Civil Protection staff were in line with international good practices and lessons learned from recent examples of complex and compound disasters around the world.

Amid the climate change, hydrometeorological hazards are increasing, disrupting activities across many sectors. To address emerging infectious diseases, robust disaster preparedness is crucial, including resilient infrastructure, effective disease surveillance, and comprehensive environmental planning.