Germs that defy antibiotics are now a major global health threat, causing near-untreatable cases of diarrhea, sepsis, pneumonia and gonorrhea, the World Health Organization said Wednesday.

Overuse and misuse of antibiotics are to blame, and the WHO’s been warning about the problem for years but it keeps worsening, says Dr. Keiji Fukuda, WHO’s Assistant Director-General for Health Security.

“We are really seeing the emergence of this all over the world,” Fukuda told a news conference.

“What it means is that all of us, all our family members…when we are most vulnerable and in need of these medicines there is simply the chance that they are not available,” he added.

“Unless we take significant actions to improve efforts to prevent infections and also change how we produce, prescribe and use antibiotics, the world will lose more and more of these global public health goods and the implications will be devastating.”

People are overusing antibiotics, experts agree. The drugs work well when used as directed against bacterial infections. But they don’t kill all the bad bugs, and the ones that survive can multiply and spread their drug-resistant genes. This happens especially when people take the wrong antibiotic, or take them to treat a viral infection, because antibiotics don’t affect viruses.

Perhaps worst of all is when people don’t take a full course of antibiotics — leaving a half-treated population of bacteria in their bodies to thrive and spread.

The WHO report finds that a drug-resistant strain of an intestinal bug called Klebsiella pneumonia has now spread to every region of the world. It withstands the effects of the treatment of last resort, a group of antibiotics called carbapenems.

“In some countries, because of resistance, carbapenem antibiotics would not work in more than half of people treated for K. pneumoniae infections,” WHO says.

It’s been a problem in the United States for decades.

Last fall, the U.S. Centers for Disease Control and Prevention reported that more than two million people are infected by drug-resistant germs each year, and 23,000 die of their infections. The biggest killer by far in the U.S. is diarrhea-causing C. difficile.

Gonorrhea may not be immediately life-threatening, but it’s developing resistance to the drugs that used to easily treat it. Patients can be left infertile.

Nearly 322,000 cases of gonorrhea were reported in the U.S. in 2011, making it the second most commonly reported notifiable infection in the nation.

The CDC asked for $30 million in the U.S. budget to open specialized labs to help spot these infections more quickly.

Overuse in farm animals is another problem.

In an attempt to help, 25 U.S. companies said earlier this year they’d phase out the use of antibiotics to help farm animals grow fatter.

“There’s been a tendency in the past for people to think that antibiotics are risk-free drugs that people should ask for and take any time they’re feeling a little bit ill. That’s not correct,” the CDC’s Dr. Steve Solomon told NBC news. “So carefully using antibiotics is really the most important thing that we can do.”