E.coli is scary — and dangerous — on its own. But new research has found drug-resistant strains of the bacteria are becoming increasingly common.

The Duke University study analyzed patient records at 26 community hospitals in the U.S. and found that the rate of drug-resistant extended-spectrum beta-lactamase (ESBL)-producing E.coli infections doubled between 2009 and 2014. (There were 5.28 infections per 100,000 patients in 2009, but that number increased to 10.5 infections per 100,000 in 2014.)

Researchers specifically studied community hospitals, where more than half of patients in the U.S. receive care.

The findings were published in the journal Infection Control & Hospital Epidemiology.

Some strains of E.coli can cause severe diarrhea, vomiting, and fever. Most people get better within five to seven days of infection, per theCenters for Disease Control and Prevention, but it can be more severe and even life-threatening for others. Children, the elderly, and people who are immunocompromised are at the highest risk for more severe complications, including hemolytic uremic syndrome, which can cause kidney failure.

While antibiotic-resistant bacteria can be problematic in some large hospitals, researchers found that there was a notable increase in infections among people who had limited exposure to health care settings (hospitals, doctor’s offices, and nursing homes) — meaning, they may have become infected through some other environmental factor.

“We primarily associate infections of this type in persons with significant health care contact,” lead study author Joshua Thaden, MD, PhD, a fellow in the Division of Infectious Diseases at Duke University Medical Center, tells Yahoo Health. “It was surprising to see such an increase in persons without such significant contact with the health care system.”

While the findings are scary, experts aren’t shocked.

“We know that some forms of bacteria have made their way out of the hospital setting and continue to spread in the community,” board-certified infectious disease specialist Amesh A. Adalja, MD, an assistant professor at the University of Pittsburgh Medical Center who was not involved in the study, tells Yahoo Health. “It’s the march of antibiotic resistant bacteria and it is going to continue.”

Government agencies have recognized that it’s a problem: The CDC listed antibiotic-resistant E.coli as a “serious” threat to public health in 2013.

Adalja points out that patients move from place to place and, with it, may carry this bacteria with them … which can then infect other people in their communities.

It’s not just spread through human contact: A study published in the journal Clinical Microbiology and Infectionfound that antibiotic-resistant E.coli is increasing in people who haven’t been hospitalized. Researchers swabbed chicken at grocery stores in Pittsburgh and found that 85 percent of the meat contained a microorganism that can produce drug-resistant E.coli.

Consequently, if people come into contact with infected meat and don’t wash their hands properly or cook it well enough, they can become infected by eating the meat or touching their nose and mouth after touching the meat.

Thaden says experts aren’t sure why antibiotic-resistant E.coli is moving beyond health care settings but says there have been cases of ESBL-producing organisms in food, water, and soil, which can then infect people. “The bottom line is that we don’t know for sure and are investigating this,” he adds.

There are some drugs that can treat ESBL, Adalja says, but the bacteria’s resistance to the most popular forms of antibiotics is problematic.

Here’s why: If a person is hospitalized with symptoms of an E.coliinfection, doctors may put the patient on one of the most popular form of antibiotics. But if the strain the person is infected with is resistant to these antibiotics, it delays the proper care the patient can receive.

“If you have to increasingly guess what the person has, you have a higher chance of getting the first antibiotic regimen wrong,” says Adalja. “But if you get it right the first time, it can save a patient’s life.”

Like MRSA, Adalja says this issue will continue to worsen as long as we’re overusing antibiotics. “It gives bacteria the ability to use their resistance mechanisms,” he says. “We’re just playing in their field when we use antibiotics when they’re not needed.”

The news sounds scary — and it is, on some level. “This is something that we should all be concerned about,” Thaden says.