She said the problem was "reaching dangerously high levels" in all parts of the world and could lead to "the end of modern medicine as we know it".
Antibiotic resistance happens when bacteria mutate and adapt to become invulnerable to the antibiotics used to treat the infections they cause. Over-use and misuse of antibiotics exacerbates the development of drug-resistant bacteria, often called superbugs.
Publishing the results of a survey of public awareness, the United Nations health agency said 64 percent of those asked believed wrongly that penicillin-based drugs and other antibiotics can treat colds and flu, despite the fact such medicines have no impact on viruses.
Around a third of people surveyed also wrongly believed they should stop taking antibiotics when they feel better, rather than completing the prescribed treatment course, the WHO said.
"The findings ... point to the urgent need to improve understanding around antibiotic resistance," said Keiji Fukuda, the WHO`s special representative for antimicrobial resistance.
"One of the biggest health challenges of the 21st century will require global behavior change by individuals and societies."
Superbug infections, including multi-drug-resistant typhoid, tuberculosis and gonorrhea, already kill hundreds of thousands of people a year, and for now the trend is still growing.
Fukuda described it as a "race against the pathogens", adding that if everyone steps into action now, it will probably take five to 10 years to turn the situation around.
The WHO surveyed 10,000 people across 12 countries -- Barbados, China, Egypt, India, Indonesia, Mexico, Nigeria, Russia, Serbia, South Africa, Sudan and Vietnam -- and found many worrying misconceptions.
Three-quarters of respondents think antibiotic resistance means the body is resistant to the drugs, for example, whereas in fact it is the bacteria themselves that become resistant to antibiotics, and their spread causes hard-to-treat infections.
Some 66 percent believe individuals are not at risk of a drug-resistant infection if they personally take their antibiotics as prescribed.
And nearly half of those surveyed think drug resistance is only a problem in people who take antibiotics often. In fact, anyone, anywhere, of any age, can get a superbug infection.
Chan urged doctors to dissuade patients from demanding antibiotics for infections they can`t treat, and persuade them to use the drugs strictly according to their prescription.
"Doctors need to treat antibiotics as a precious commodity," she said.
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