Huge hydroelectric projects (see, for example, Nature 478, 305–307; 2011) can have a negative impact on public health, particularly in tropical areas. Public and private power companies should be obliged to assess this risk and incorporate it into their development policies.

It was pointed out ten years ago that the World Commission on Dams, created in 1998 by the World Bank and the International Union for Conservation of Nature, had fallen short in analysing health issues (A. C. Sleigh and S. Jackson Lancet 357, 570–571; 2001). This oversight has still not been rectified: the Strategic Environmental Assessment of Hydropower on the Mekong Mainstream, for example, did not include public-health risks or the likely consequences in its report.

The failure to develop strategies to mitigate emerging or re-emerging infectious diseases in this context probably stems from ignorance and financial considerations. Reliable analysis of environmental and societal health risks is essential for their prevention and control, which depend on evidence-based guidance for health policy and planning. It is also crucial to optimize integrated surveillance systems to allow timely responses to public-health threats.

The 1,070-megawatt Nam Theun 2 hydropower station in central Laos has shown that long-term surveillance and monitoring of vector-borne diseases is achievable at an acceptable cost.