Six-week window after floods critical for public health, says study

Floods heighten risk of death in the three to six week-window following the event, new research in the British Medical Journal (BMJ) says.

The risk of death in general increased by 2.1 per cent, whereas that for people with heart and lung illnesses increased by 2.6 and 4.9 per cent respectively, a team of researchers led by those at Australia's Monash University found.

This increased risk peaks for around 25 days but persists for up to 50-60 days after the first day of flooding, they said in their study, having studied deaths in 761 communities from 35 countries that experienced at least one flooding event from 2000 to 2019.

In the aftermath of a flood, risk of deaths from natural causes could be enhanced by contamination of food and water, exposure to disease-causing fungi, bacteria or virus, impaired access to health services, and psychological impairment.

These flood-and-death associations varied with local climate types and were stronger in populations with low socioeconomic status or greater numbers of older people, said lead researcher Yuming Guo from the university's School of Public Health and Preventive Medicine, whose team analysed a total of 47.6 million deaths from all causes, 11.1 million cardiovascular deaths, and 4.9 million respiratory deaths.

"Do mortality risks change after floods in the general population? The answer is yes, and this needs to be factored into policy responses to flooding events," said Guo.

Against the backdrop of climate change, flooding events, which account for nearly half (43 per cent) of all natural disasters, are projected to become more severe, longer and more frequent.

Roughly 23 per cent of people are directly exposed to inundation depths of over 0.15 metres every decade, the researchers said.

Southeast Asian communities were among those who experienced the most flood days per year during the study period. Other communities were those from areas along the Mississippi river in the US, the Pacific coast of Latin America, Lake Victoria and the Volta in Africa, the coastal areas of mainland China, and the eastern coast of Australia, their study found.

They said that their study provides a timeline of public health consequences of flooding events, including giving health authorities and policy makers a blueprint of when they should actively monitor flood-affected communities.

"(Healthcare providers) should incorporate this knowledge into their practice and be prepared for the suddenly elevated demands of health services to reduce avoidable deaths from natural causes," said Guo.

"Public health institutions should monitor the changes in mortality rate in the 25 days following floods to enable prompt interventions.

"Policymakers should prioritise comprehensive disaster preparedness, early warning/detecting systems, and efficient disaster response protocols to reduce the attributable deaths due to floods - including climate change adaptation measures because of projected increases in floods globally," said Guo.