(CNN) Seven gonorrhea patients in Hawaii make up the first known US case cluster in which the sexually transmitted infection showed reduced susceptibility to the single available effective treatment option, the Centers for Disease Control and Prevention said today. The patients were diagnosed in April and May.

The six men and one woman were all cured by ceftriaxone and azithromycin, the two-drug regimen recommended for treating gonorrhea by the CDC. However, laboratory tests by the Hawaii State Department of Health showed that the patients' gonorrheal infections did not succumb as easily to the antibiotics as infections have in the past.

"Since 2005, we have seen four isolated cases that showed resistance to both drugs. But the Hawaii cases are the first cluster we have seen with reduced susceptibility to both drugs," said Paul Fulton Jr., a spokesman for the CDC.

This increased resistance serves as an early warning sign, the CDC explained at the 2016 STD Prevention Conference in Atlanta. Someday, these antibiotics may no longer work to cure gonorrhea, which, over the years, has developed resistance to nearly every class of antibiotics used to treat it.

A common STD

The CDC estimates that there are 800,000 gonorrhea infections in the US each year, though many go unnoticed and untreated, said Dr. Jonathan Mermin, director of the CDC's National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention.

Symptoms include a burning sensation when urinating and unusual discharge from the penis or vagina. Left untreated, the infection can cause serious health problems including long-term abdominal pain and pelvic inflammatory disease, which could lead to ectopic pregnancy and infertility.

Increased gonorrhea screening is absolutely essential, said Dr. Gail Bolan, director of the division of STD Prevention at the CDC.

"Gonorrhea is one of the most common sexually transmitted infections, but most people do not realize they have it. The only way they find out is through testing," she said.

When health care providers do not treat according to the CDC's two-drug regimen -- a single shot of ceftriaxone and an oral dose of azithromycin -- patients may feel better, and their symptoms may disappear, but they may still have the infection incubating inside them, explained Bolan.

"If you're not treated correctly, you cannot rely on your symptoms to tell you you've been cured," she said.

Though no failures of the current treatment regimen have been confirmed in the United States, the CDC has been closely monitoring antibiotic resistance.

"We usually see emerging decreased susceptibility or resistance coming from the West, starting with Hawaii, and then we also see a higher proportion of isolates with decreased susceptibility in men who have sex with men. This is a pattern we've seen with penicillin resistance and other antibiotics," Bolan said.

The threat of increased drug resistance is not an issue affecting gonorrhea alone. Today, the UN General Assembly convened a high-level meeting for member states, nongovernmental organizations, the private sector and academic institutions to provide input on the issue of antibiotic resistance. Overuse of antimicrobial medicines for both humans and animals and use of antibiotics in agriculture have all contributed to the problem.

Treatment-resistant infections threaten humanity, say experts, who warn that simple infections might soon be untreatable with existing drugs.

While the CDC attempts to preserve the effectiveness of its two-antibiotic regimen, new drug candidates are being tested to fill expected gaps in the arsenal against gonorrhea and other infections. One antibiotic showed promise in a recent clinical trial testing for safety in humans.

Experimental drug offers hope

Dr. Stephanie Taylor, a professor of medicine and microbiology at Louisiana State University Health Sciences Center, said an experimental drug, ETX0914, represents a new class of antibiotic since it works differently from other marketed drugs.

In a phase 2 trial, lead researcher Taylor and her colleagues treated patients with gonorrhea using ETX0914 alone at either 2g or 3g dosage levels. All patients treated at the higher dosage level and 98% at the lower dosage level were cured. Though a small number of patients reported side effects, they were mild and primarily gastrointestinal.

Pleased with the results, Taylor hopes ETX0914 advances through additional trials of its effectiveness.

The CDC will be bolstering state and local STD programs and introducing laboratory tools and services to more rapidly respond to outbreaks. "We are scaling up our detection efforts," said Bolan.