The deaths of two patients at the Ronald Reagan UCLA Medical Center have been linked to antibiotic-resistant bacteria, the hospital reported Wednesday. Seven other patients were known to have been infected, and over 175 others could have been exposed to it. This is not the first time this particular strain of bacteria, carbapenem-resistance enterobacteriaceae (CRE), has appeared in hospitals in the United States, and it’s unlikely to be the last.

Antibiotic resistance is a growing danger around the world, one that the World Health Organization considers “an increasingly serious threat to global public health.” It has warned, “The world is heading towards a post-antibiotic era, in which common infections and minor injuries, which have been treatable for decades, can once again kill.”

New cases of multi-drug infections emerge every year, and bacteria that cause common infections like urinary tract infections or pneumonia tend to have high rates of resistance to antibiotics. Antibiotic resistance is common enough that levels of resistance are sometimes incorporated into the names of certain bacteria, like MRSA, which stands for methicillin-resistant staphylococcus aureus.

Carbapenem-resistance enterobacteriaceae (CRE) is resistant to most known antibiotics, including, as its name implies, carbapenems, a class of broad-spectrum antibiotics. They have been a critical weapon in the antibiotic arsenal, as they can treat the widest range of infections in comparison with other classes of drugs, and are a drug of last resort to treat many bacterial infections, including those caused by antibiotic resistant drugs. But globally, studies show that resistance to carpabenems is growing.

Antibiotic resistance is a subset of antimicrobial resistance, a broader term that refers to the resistance of microorganisms to drugs used to treat infections caused by those microorganisms, such as bacteria, fungi, viruses and parasites. Factors that contribute to antibiotic resistance include improper use of antibiotics, such as not taking a course of medication for the full period prescribed, or using antibiotics to try and treat a viral illness, as well as antibiotics’ increasing use in livestock. When antibiotics are taken insufficiently, they can fail to wipe out all the bacteria they’re prescribed to kill, and surviving bacteria can develop resistance to that drug.

The Centers for Disease Control and Protection (CDC) has said that CRE can contribute to death in up to half of those who are seriously infected with it. Every American state except for Idaho, Alaska and Maine have reported infections of CRE. The CDC also estimates that 2 million people in the United States become infected each year with resistant bacteria and that at least 23,000 die annually as a result.

A spokeswoman for the UCLA hospital said that the CRE bacteria may have been transmitted through two endoscopes, which the hospital said it had sterilized according to the manufacturer’s instructions. The hospital is contacting 179 other patients who had endoscopic procedures between October 2014 and January 2015 who may have also been exposed to the bacteria. It is sending them home-testing kits that UCLA will then analyze.