The World Health Organisation (WHO)says common infections can once again be considered potentially fatal because of growing resistance worldwide to antibiotics.
In a comprehensive global study of the topic released overnight, the United Nations organisation says the world is headed for a post-antibiotic era.
The organisation analysed data from 114 countries and said resistance was happening now in every region of the world.
It described a post-antibiotic era, where people die from simple infections that have been treatable for decades.
There were likely to be devastating implications unless significant action was taken urgently, it added.
The report focused on seven different bacteria responsible for common serious diseases such as pneumonia, diarrhoea and blood infections.
It suggested two key antibiotics no longer work in more than half of people being treated in some countries.
One of them - carbapenem - is a so-called last-resort drug used to treat people with life-threatening infections such as pneumonia, bloodstream infections, and infections in newborns, caused by the bacteria K.pneumoniae.
Bacteria naturally mutate to eventually become immune to antibiotics, but the misuse of these drugs - such as doctors over-prescribing them and patients failing to finish courses - means it is happening much faster than expected.
The WHO said more new antibiotics need to be developed, while governments and individuals should take steps to slow this process, the BBC reports.
In its report, it said resistance to antibiotics for E.coli urinary tract infections had increased from "virtually zero" in the 1980s to being ineffective in more than half of cases today. In some countries resistance to antibiotics used to treat the bacteria would not work in more than half of people treated.
Low rates of resistance in NZ
An antibiotics specialist in New Zealand says more research is needed to find out how much of a problem drug resistance is in the country.
Environmental Science and Research clinical microboiologist Deborah Williamson said New Zealand has low rates of antibiotic resistance compared to other countries but should not be complacent.
"One of the big knowledge gaps is how much antibiotic is used and who gets it, and that's something that people are actively looking at at the moment," she said.