Infections caused by an uncommon superbug—one resistant to several kinds of antibiotics—are increasingly showing up in a Houston hospital system, according to new research published Tuesday in the journal mBio.

Researchers from the Houston Methodist Research Institute sequenced the genomes of many different strains of the bacteria Klebsiella pneumoniae, which caused 1,777 infections in the Houston Methodist hospital system from 2011 to 2015. K. pneumoniae is known to cause serious health problems, including pneumonia and bloodstream infections.

They found that an uncommon strain, clone type 307, was the most prevalent.

MORE: I Survived Flesh-Eating Bacteria—And It Changed My Life Forever

“It’s like if I told you that all around the world, 80% of cake is vanilla,” says study author Dr. S. Wesley Long, associate director of the Clinical Microbiology Laboratory at Houston Methodist Hospital. “We come to Houston and we expect to find vanilla cake, but half of the cakes are red velvet.”

Why this rare strain is so common among Houston patients is not yet known, but it has recently been shown to be resistant to several types of antibiotics. In January, officials at the U.S. Centers for Disease Control and Prevention (CDC) reported that a Nevada woman had died from a K. pneumoniae infection after it was unresponsive to 26 different antibiotics.

The Houston researchers say that while there is resistance, the strain is still responsive to certain antibiotics.

“We are still trying to come to terms with what the implications are,” says Long. “We don’t want to alarm anyone, because the local superbug is no more virulent than the other [strains]. There’s nothing about it that makes it any worse for patients or requires it to be treated differently.”

Get our Health Newsletter. Sign up to receive the latest health and science news, plus answers to wellness questions and expert tips. Please enter a valid email address. Sign Up Now Check the box if you do not wish to receive promotional offers via email from TIME. You can unsubscribe at any time. By signing up you are agreeing to our Terms of Use and Privacy Policy . This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply. Thank you! For your security, we've sent a confirmation email to the address you entered. Click the link to confirm your subscription and begin receiving our newsletters. If you don't get the confirmation within 10 minutes, please check your spam folder.

Contact us at letters@time.com.