Thomas Barwick | Stone | Getty Images

For the first time in its history, the Centers for Disease Control and Prevention is categorizing drug-resistant superbugs by threat level. On Monday, the CDC issued its highest level of warning for a drug-resistant strain of gonorrhea—saying the sexually transmitted disease is an "urgent threat" to the health of Americans. "We've been raising this issue for some time, and the CDC just confirms how serous the problem is," said William Smith, executive director of the National Coalition of STD Directors, a nonprofit group that provides services and programs to fight sexually transmitted diseases and works with the CDC.

"There's no question gonorrhea is developing resistance to every drug created to fight it," Smith said. (Read more: US cancer care in crisis, experts say) Some 820,000 cases of gonorrhea are reported in the U.S. every year, making it the second most reported communicable disease behind another sexual disease, chlamydia. According to the CDC, an estimated 246,000 of those gonorrhea cases are of the drug-resistant strain.

Medical costs in the millions

The term superbug is commonly used to describe any microorganism that is resistant to at least one or more commonly used antibiotics. The CDC says that if a drug-resistant strain of gonorrhea becomes widespread over a 10-year period, there will be an estimated 75,000 additional cases of pelvic inflammatory disease—which causes infertility. And there would be hundreds of additional HIV cases. The CDC estimates that direct medical costs if the strain spreads will be $235 million over the 10 years, but that costs would likely be even higher due to case management and patient follow-ups with doctors. "We can pay the costs of this going forward or do the investing now," said Smith, whose group has called for some $54 million in spending by Congress for proper diagnosis and development of an antibiotic to treat the strain. So far, the strain of gonorrhea, called Neisseria gonorrhoeae, is showing resistance to the current and strongest antibiotic in use, called ceftriaxone, which is administered by a painful injection, Smith said. (Read more: Priced to sell: Sweet Obamacare deals for young)



Number of cases of resistance or reduced susceptibility Percentage Estimated number of cases Gonorrhea 820,000 Resistance to any antibiotic 30% 246,000 Reduced susceptibility to cefixime <1% 11,480 Reduced susceptibility to ceftriaxone <1% 3,280 Reduced susceptibility to azithromycin <1% 2,460 Resistance to tetracycline 23% 188,600

23,000 die each year