Concern about growing global antibiotic resistance has come to a head: The World Health Organization is now warning that the world is running out of antibiotics.

There aren’t enough truly new antibiotics being developed, especially for the most concerning antibiotic-resistant infections, according to a WHO report released Tuesday.

The United Nations health agency has aired its concerns about antibiotic resistance, which makes it more difficult to treat infections, for some time. Some of the group’s latest moves included updating guidelines for treating sexually transmitted infections and cautioning that just three antibiotics are being developed to treat gonorrhea, a “fairly grim” situation.

But the latest WHO report takes a broad and prospective look at antibiotic development, and what it describes is not a pretty picture.

“Antimicrobial resistance is a global health emergency that will seriously jeopardize progress in modern medicine,” said Tedros Adhanom Ghebreyesus, the WHO’s director-general. Without more investment in research and development, “we will be forced back to a time when people feared common infections and risked their lives from minor surgery.”

Related: The World Health Organization just put out a dire warning about untreatable gonorrhea

Public health officials have long been concerned about antibiotic resistance, which occurs when bacteria mutate and become immune to a given antibiotic. Overuse or incorrect use of antibiotics are key contributing factors, as is antibiotic use in animals that are then consumed by humans.

But drug development is lagging behind, especially for drug-resistant tuberculosis and other infections the WHO has designated as high priority, the U.N. health agency said.

Of 51 new products in development for antibiotic-resistant infections, the WHO believes that only eight are innovative and add value to current options. And because drug development is a drawn-out process, most of it unsuccessful, current efforts could result in only about 10 new approvals in the next five years, the report said.

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Even then, “these potential new treatments will add little to the already existing arsenal” because most of the products being developed today are essentially versions of existing antibiotic classes, the report said. Thus, most products usually can’t work against many current types of resistance, and will only be helpful in the short term.

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Fifty-one new antibacterial agents are currently in the early to late stages of clinical development, according to a new World Health Organization report. World Health Organization

And for drug-resistant diseases that should be high priority, there aren’t enough oral antibiotics, which are used to treat infections outside of a medical setting or in places where resources are limited, the agency said.

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Another problem is limited involvement by drugmakers, in large part because antibiotics just aren’t very profitable. Antibiotics are typically low-priced, and any last-resort antibiotics would likely be used infrequently. Much of new antibiotic development is underwritten at least in part by public or philanthropic research grants, the WHO report said.

U.K.-based Summit Therapeutics SMMT, +1.19% , for example, is developing the antibiotic ridinilazole for C. difficile infection, which causes colon inflammation and symptoms like diarrhea and fever.

But initially, there was no investor interest in the antibiotic, Summit management told MarketWatch early this year, and early development through a phase 2 clinical trial was supported by U.K.-based charitable foundation the Wellcome Trust.

The antibiotic had positive results in early data from the phase 2 trial, the company said this month, and it now numbers among seven antibiotics being developed for C. difficile, according to the WHO report.