A little-known sexually transmitted disease that has attracted more attention lately may actually be fairly common, according to a new study.

The study found that the bacterium Mycoplasma genitalium, which is thought to be sexually transmitted, infects more than 1 percent of people ages 16 to 44 in the United Kingdom. That comes out to about 250,000 people, according to U.K. census data. Studies in the United States have found that a similar percentage of people here are infected with M. genitalium.

That makes M. genitalium a more common sexually transmitted disease (STD) than gonorrhea, according to the Centers for Disease Control and Prevention.

Here's what you need to know about Mycoplasma genitalium:

Is this a new STD?

Some news outlets have described M. genitalium as a "new" sexually transmitted infection, but the bacteria were first discovered in 1980. At this time, researchers didn't have the right types of test to study M. genitalium, so the connection between M. genitalium and sexual activity came a little later — around the mid-1990s, said Lisa Manhart, a professor of epidemiology at the University of Washington in Seattle, who was not involved in the new study, but has researched M. genitalium. For example, early studies found that people who tested positive for M. genitalium often had sexual partners who were infected with the disease as well.

The new study adds to the evidence that M. genitalium is an STD, because it found that the infection was more common in people who had at least four new sexual partners in the past year than in people who had one or fewer new partners in the past year. In addition, people were more likely to have M. genitalium if they had unprotected sex, and no infections were found in people who had never had sex, according to the study, which was published Nov. 3 in the International Journal of Epidemiology.

What symptoms does it cause?

In men, the bacteria can cause inflammation of the urethra (called urethritis) that leads to symptoms such as a burning pain while urinating or discharge from the penis.

Whether M. genitalium causes disease in women is less clear, but the bacteria have been linked to inflammation of the cervix (cervicitis), as well as pelvic inflammatory disease, an infection of the female reproductive organs that can lead to pain in the lower abdomen and pain or bleeding during sex, according to the CDC. In severe cases, pelvic inflammatory disease can lead to infertility in women.

"Most of the research that’s going on now is trying to better understand the implications of [M. genitalium] infection in women," Manhart said. A recent review study by Manhart and colleagues found that the risk of inflammation of the cervix, pelvic inflammatory disease and preterm birth was about twice as high in women with M. genitalium infection, compared to women without the infection. Still, some researchers want to see more evidence before concluding that M. genitalium does cause complications in women, Manhartsaid.  

The new study in the International Journal of Epidemiology found that about 94 percent of men and 56 percent of women infected with M. genitalium did not have symptoms.

Should people be tested for it?

The U.S. Food and Drug Administration has not approved a test for M. genitalium, and doctors do not routinely test for the bacteria, said Dr. Jamin Brahmbhatt, a urologist at Orlando Health in Florida. However, doctors may consider testing for M. genitalium in patients who have persistent symptoms after treatment for other sexually transmitted diseases that can cause similar symptoms, said Brahmbhatt, who was not involved in the study but treated people with M. genitalium infections.

More research is needed to better understand how common M. genitalium is among people in the U.S., and whether routine screening for the bacteria may be warranted, he said.

Do you need to treat it?

The antibiotics that are generally recommended to treat urethritis, cervicitis and pelvic inflammatory disease are usually not very effective against M. genitalium, Manhart said. So doctors might suspect that a patient has M. genitalium if he or she doesn't get better after taking the drugs typically used to treat these other STDs. Doctors could then provide other antibiotics that are more effective against M. genitalium, Manhart said.

Treatment for M. genitalium is often a five-day course of antibiotics, Brahmbhatt said.