Multidrug-resistant E. coli were found in 40% of store-bought meat samples tested in one Spanish city in 2020, according to data that will be presented this weekend at the European Congress of Clinical Microbiology & Infectious Diseases in Copenhagen.

Researchers analyzed 100 samples—25 each of chicken, turkey, beef, and pork—from supermarkets in Oviedo, Spain, during the first year of the pandemic. 

The good news: The majority (73%) of the samples contained E. coli., but levels that were within food safety limits.

The kicker: Nearly half contained multidrug resistant and/or potentially disease-causing E. coli. Forty contained E. coli resistant to most penicillins and cephalosporins, common antibiotics. And nearly a third contained E. coli that can cause issues outside of the GI tract, like urinary tract infection, sepsis, and/or neonatal meningitis.

What’s more, one sample contained a type of E. coli resistant to colistin, a last-resort antibiotic used to treat infections resistant to all other antibiotics.

Tips for safely preparing and serving meat

The researchers, Azucena Mora Gutiérrez and Vanesa García Menéndez from the University of Santiago de Compostela-Lugo in Lugo, Spain, had previously discovered similar findings in chicken and turkey. Their latest research, they say, shows that danger is posed by beef and pork as well.

Mora’s advice to consumers who wish to reduce their risk of becoming ill from meat:

• Ensure the cold foods you buy from the supermarket remain cold on your way home, and that you properly store them right away.
• Cook your meat thoroughly.
• Be sure to disinfect your knives, chopping boards, and other cooking utensils between uses.

“With these measures, eating meat becomes a pleasure and zero risk,” she says in a release about the research.

Most strains of E. coli are harmless, according to the CDC. But some can make you sick, causing diarrhea, urinary tract infections, respiratory illnesses, pneumonia, and other illnesses.

The growing problem of drug resistance

The new research highlights the growing concern regarding antimicrobial resistance, one of the top 10 public health threats facing humanity, according to the World Health Organization. Antimicrobial resistance occurs when bacteria, viruses, fungi, and parasites evolve over time, becoming less responsive to medicines—and making infections increasingly difficult, or impossible, to treat.

Antibiotic resistance refers just to resistance from bacteria. Alone, it kills an estimated 700,000 people globally each year, according to the World Health Organization. That number could rise to 10 million by 2050 if action isn’t taken, the organization says.

“We are watching this antibiotic era turn into a post-antibiotic era,” Dr. Michael Osterholm, director of the University of Minnesota’s Center for Infectious Disease Research and Policy (CIDRAP), recently told Fortune. “That is a scary proposition.”

Global efforts are underway to slow the increase of resistance, since it’s an impossible process to stop, he said. But little is being done in this regard, or to develop new treatments. A November 2021 statement by the WHO called the clinical pipeline of new antimicrobials “dry.”

It wasn’t so long ago that “children died all the time from bacterial infections that today we wouldn’t think twice about,” Osterholm said.

“Our great-grandparents grew up in a pre-antibiotic era,” he said. “My generation, in large part, and my kids’ generation, grew up in an antibiotic era. Our grandkids and great-grandkids are clearly going to be living—at least in many areas of the world—in a post-antibiotic era.”