Gonorrhea is one of the most common sexually transmitted infections around, and is easily treatable by a number of antibiotics. According to a report from Philly.com, however, one of the most common antibiotic treatments, cefixime, has been growing less and less effective against the infection.

A new study from the Centers for Disease Control and Prevention shows that while resistance to cefixime dropped between 2011 and 2013, it began to rise again last year. Officials are worried that it will only continue to rise in the future.

Cefixime isn’t typically first on the list of treatments for gonorrhea infections, and is usually only used when the first treatment, ceftriaxone-based combination therapy, is not available. The CDC indicated no changes to the effectiveness of the combination therapy that is primarily used.

The discovery could foreshadow an increasingly resistant gonorrhea, which has worried many doctors. According to the study’s head author, Dr. Robert Kirkcaldy, an epidemiologist at the CDC’s division of STD prevention in Atlanta, it is imperative that doctors continue to monitor how quickly these diseases are growing drug resistant capabilities. He believes that the finding should provide the motivation to study why the drug has become less effective and what health officials can do to prevent further drug resistance.

The study, which was published in the Journal of the American Medical Association, says that gonorrhea is typically spread through unprotected vaginal, oral, or anal sex, and is most common among teens and young adults between the ages of 15 and 24.

Symptoms of gonorrhea can vary widely. Infected men can experience swollen testicles and a strange colored discharge. In women, symptoms can include vaginal discharge and bleeding in between menstruation. In both genders, painful sensations while urinating and rectal infections, which can lead to soreness, itching, bleeding, discharge, and painful bowel movements are typical symptoms of the disease.

If left untreated, gonorrhea can cause serious problems down the road. It can lead to chronic pain in the pelvis, infertility, and ectopic pregnancy, one that occurs outside of the uterus and can threaten the life of both the mother and the fetus.

Antibiotics have been the treatment of choice for the disease. The CDC study examined treatment outcomes for male patients who received treatment from public clinics between 2006 and 2014. They examined over 51,000 samples from 34 different cities.

The CDC officials fear that the declining effectiveness of cefixime will foreshadow a drop in effectiveness for ceftriaxone, and plan to continue monitoring resistance to both treatments over future large-scale studies.