As bacteria and other pests evolve to evade medications, infections that were once easily cured with a few pills or creams can become chronic or even deadly.
According to Dr. Margaret Chan, director general of the World Health Organization, "Things as common as strep throat or a child's scratched knee could once again kill."
The most worrisome development for experts is the rise of bacteria immune to normal antibiotics.
"We are losing our first-line antimicrobials," Chan said in her keynote address at the conference on combating antimicrobial resistance in 2012. "Replacement treatments are more costly, more toxic, need much longer durations of treatment, and may require treatment in intensive care units."
Other organisms have also evolved to evade human remedies.
Pests such as lice are becoming nagging problems as well, as they produce stronger eggs and become resistant to the old medications that have usually kept them in check.
Approximately 12 million American children become infected with the tiny pests each year.
With mutant bugs and bacteria on the loose, ABC News asked infectious disease experts which superbugs pose the biggest threats.
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