In the 1840s, the Hungarian physician Ignaz Semmelweis made a startling observation: Women were five times more likely to die from childbirth when cared for by doctors rather than midwives.
Believing that doctors performing autopsies were spreading infections to mothers, he made handwashing at his hospital mandatory and drastically reduced maternal deaths. The simple lesson was this: Good hand hygiene is important, not simply for our own benefit, but to avoid harm to others.
Public health is full of such salutary lessons. The 19th century British reformer Edwin Chadwick showed that living conditions among the poor affected their health and life expectancy. The subsequent Victorian sanitary reforms vastly improved the health of Britain's population, much as they did in Singapore's younger days.
But in 1928, Alexander Fleming made a discovery that revolutionised medicine. A mould that had contaminated bacterial cultures in his laboratory produced a substance that killed the bacteria.
The antibiotic era was born.
Infections that once killed could be treated with a simple course of penicillin. Procedures that make the body vulnerable to infections, including chemotherapy and transplantation, were made possible by antibiotics to counter these infections. Soon, we thought, infectious diseases would cease to plague humanity.
Yet antibiotics are not the silver bullet we once believed. Gradually, bacteria have evolved mechanisms to counteract these antibiotics.
Widespread antibiotic use has enabled resistant bacteria to thrive. Globally, antimicrobial-resistant infections kill 700,000 people each year. Without drastic action, this figure will rise 10-fold by 2050; half of those deaths will occur in Asia.
Antibiotic resistance is a classic example of the tragedy of the commons: while we all benefit from appropriate antibiotic use, the harmful consequences of misuse, such as resistant infections, usually affect others. Consequently, we have little incentive to use antibiotics cautiously. But the more we use antibiotics, the worse off we are as a society.
The evolution of resistance is innate to the survival of bacteria and other microbes, but the problem of antimicrobial resistance is man-made, a result of overuse and misuse of antimicrobial drugs, especially antibiotics.
Half of all antibiotics are used in agriculture. Of these, 70 per cent are antibiotic classes important in human medicine. Antibiotics are so cheap that entire fish farms and herds of pigs, poultry and cattle can be treated with them to promote faster growth or prevent infection.
The high densities in which food animals are reared to meet global demand for animal protein would not be possible without antibiotics. The economic benefits to agricultural producers of using antibiotics in this way are substantial, but the health and societal consequences could be disastrous. There is increasing scientific evidence of resistant bacteria emerging from antibiotic use in food animals and spreading to humans.
Simultaneously, antibiotic misuse in human and veterinary medicine has contributed to the rise in so-called superbugs.
Around 80 per cent of human-use antibiotics are prescribed in primary care. Of these, half are used to treat infections for which antibiotics are ineffective, such as colds and flu. Often, infections are treated with broad-spectrum antibiotics that target many bacterial species.
But killing antibiotic-sensitive bacteria indiscriminately helps antibiotic-resistant bacteria to thrive without competition. And because resistant bacteria can spread between people even if they have no symptoms, gradually our existing arsenal of antibiotics becomes less effective for patients who really need them.
Increasingly, doctors face patients with infections that are untreatable, or treatable only with costly and more toxic last-resort drugs.
Antibiotic resistance is a classic example of the tragedy of the commons: While we all benefit from appropriate antibiotic use, the harmful consequences of misuse, such as resistant infections, usually affect others. Consequently, we have little incentive to use antibiotics cautiously. But the more we use antibiotics, the worse off we are as a society.
And because antibiotics are used for short periods, they are less profitable than other drugs, which dissuades pharmaceutical companies from investing in them - no new antibiotic class has been developed for the past 30 years.
The problem is so urgent that it was specifically discussed by the United Nations General Assembly in September, only the fourth time a health-related issue has been discussed in that forum.
The resulting declaration was heartening, an affirmation by world leaders to tackle antimicrobial resistance by committing to better monitoring, preventing infection through immunisation and improved sanitation, developing diagnostics to target antibiotics appropriately, creating financial incentives for antibiotic discovery, reducing overuse while improving access where they are needed most, and enhancing education on prudent antibiotic use.
This list underlines the scale of the challenge and reminds us that in public health, there are no silver bullets.
Disjointed policies will not work for a problem as complex as antimicrobial resistance. Instead, we need to rethink how we as a society mobilise our institutions to address global challenges, safeguard the health of current and future generations, and ensure that the health advances of the past century are not undone.
The UN declaration is a welcome step, but we should not simply rely on governments or the scientific community to act. An effective response will require coordination between national institutions, international governments and the private sector, sustained investments in sanitation and health systems, and decades of research and implementation.
But you can act now.
You can help reduce demand for antibiotics by pledging to take a few key steps. You can reduce your own and others' risk of infections by keeping up to date with vaccinations and maintaining good hand hygiene.
You can demand better information about how the food you eat is produced, and you can choose to reduce consumption of and demand for animal products produced using irresponsible practices. You can demand more action to prevent transmission of antibiotic-resistant bacteria and other infections in our hospitals and healthcare institutions, which have a responsibility to safeguard our health.
And you can choose to use antibiotics responsibly by acting on public health's salutary lessons.
The next time you experience a minor ailment, you can question whether you really need a course of antibiotics, not simply because it might not do you any good, but because it could prevent doing harm to others.
It is for good reason that the theme for this year's World Antibiotic Awareness Week - an event supported by the World Health Organisation (WHO) that started on Monday - is "Antibiotics: Handle with care".
Far from being a panacea for ailments, antibiotics should be treated with care and respect, as a finite, precious resource threatened by the global rise in antibiotic resistance.
• The writer is assistant professor at the Saw Swee Hock School of Public Health, National University of Singapore.
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