In home and hospital, town and city, high-quality water, sanitation and hygiene is a vital and cost-effective means to beat back AMR’s rapid emergence. It is a means we must harness effectively Clean, safe and well-managed water is fundamental to public health. Where water is unclean or sanitation poor, life-threatening diseases such as cholera and typhoid can take root. And where water is unregulated or enforcement lax, contamination from chemicals, pathogens or excreta is a persistent risk. Poor hygiene, meanwhile, exacerbates each of these problems, amplifying one of humanity’s gravest health security threats: antimicrobial resistance. Antimicrobial resistance (AMR) occurs when the effectiveness of antimicrobial drugs – including antibiotics – is diminished due to mutations in infectious bacteria. This happens when antibiotics are ill-regulated and overused, or when they are used inappropriately or for non-human health. Bacterial mutations and the superbugs they create make treating basic infections such as skin sores or diarrhea next to impossible. They also make surgery risky. Around 700000 people across the globe already die of AMR each year. If present trends persist, by mid-century AMR will kill more people than cancer. So where do water, sanitation and hygiene come in? To start with, poor sanitation and unsafe water cause a range of bacterial infections that heighten antibiotic usage. Though access across the South-East Asia Region to improved water sources is now at 90%, poor operation and maintenance of water and sanitation systems continues to be a fact of life for many. Millions of people region-wide remain susceptible to water-borne diseases, with high rates of infection compounded by self-medication and inappropriate antibiotic use. Next, poor water, sanitation and hygiene (WASH) in health care facilities is a cause of hospital-acquired infections that accelerate bacterial mutations. Just 38% of health care facilities in low- and middle-income countries have rudimentary WASH amenities, resulting in the incubation of a range of deadly pathogens. And finally, ill-regulated waste water is scattering antibiotic residues and antibiotic-resistant bacteria throughout the environment, including in drinking water and the food chain. Across the region, contaminated wastewater from homes, hospitals, pharmaceutical industries, nursing homes and livestock farms is finding its way into natural water sources, as well as soil and crops. This is hastening the spread of antibiotic-resistant pathogens, and increasing human antibiotic consumption. As countries finalize National Action Plans to counter AMR, a return to core WASH principles is needed.  By including WASH in multi-sectoral planning, and staying true to a ‘One Health’ approach, governments can neutralize one of AMR’s key accelerators and help reverse AMR’s growing menace. There are three interventions that will have immediate impact. First, governments can hasten efforts to achieve safe water and sanitation for all. Communities lacking clean water and effective sanitation should be identified in both rural and urban areas, and steps taken to ameliorate their situation. This could mean treating water at its point of use or systematizing the operation and maintenance of local water supply systems. It could also mean investing in water supply systems to serve unreached populations. Second, WASH amenities and training can be enhanced at all healthcare facilities. This can be done by ensuring each facility has a safe and adequate water supply, and that toilets and medical waste management facilities are in or near it. Hand-washing stations should be readily accessible at key points of care, and health care workers should be trained in WASH procedures as part of wider infection prevention and control initiatives. And third, regulation and treatment of wastewater can be vastly improved. To do so, investing in water management and treatment infrastructure is crucial, while creating public-private partnerships able to extend service coverage may also be effective. Key contaminators such as hospitals and pharmaceutical plants can meanwhile be encouraged – or required – to develop onsite treatment plants able to neutralize antibiotics and resistant bacteria. Wastewater used in aquaculture and agriculture should also be better regulated to keep water and food systems free of potentially harmful residues and bacteria. Though each of these interventions will have substantial impact, they must be supported by surveillance systems that can monitor the problem effectively and allow policymakers in all sectors to respond as and where needed. There is much that we still do not know about the quantity of antibiotics and resistant bacteria in the environment, and the various ways it got there, meaning gathering actionable information is crucial. Reversing AMR and safeguarding the efficacy of our most precious drugs – antibiotics – is a complex undertaking. It requires addressing how antibiotics are produced and regulated; how they are prescribed and consumed; and how different sectors can work together to counter a range of AMR-related threats. It is an undertaking for which WASH principles are well-suited, and for which WASH resources should be marshalled. In home and hospital, town and city, high-quality water, sanitation and hygiene is a vital and cost-effective means to beat back AMR’s rapid emergence. It is a means we must harness effectively. Singh is Regional Director, WHO South-East Asia