An explosion of reported early syphilis cases in Clark County since 2012 has been deemed an outbreak by the Southern Nevada Health District.

The monument sign for the Southern Nevada Health District is seen on Friday, Oct. 17, 2014. (David Becker/Las Vegas Review-Journal)

An explosion of reported early syphilis cases in Clark County since 2012 has been deemed an outbreak by the Southern Nevada Health District.

Reported cases of the sexually transmitted disease have skyrocketed 128 percent in Southern Nevada since 2012, with 694 new-onset cases of the disease confirmed in 2015, the health district said.

An early syphilis case is one that has been contracted over the past 12 months, the health district said in a statement.

“We are considering this an outbreak because disease rates in our community are continuing to climb and we see no plateau at this point,” health district Chief Health Officer Dr. Joe Iser said in the statement.

The recent boom in Clark County early syphilis cases is limited to Clark County residents, health district medical epidemiologist Dr. Tony Fredrick said.

Fredrick said it’s unclear why the number of cases has jumped but the health district is investigating.

Syphilis can be spread sexually and from mother to child during pregnancy, according to the Centers for Disease Control and Prevention. It can be easily cured with penicillin during its early stages, but if late-stage syphilis develops, generally 10 to 30 years after initial infection, symptoms can include paralysis and internal-organ damage that cannot be undone by typical syphilis treatment.

In the disease’s primary stage, a firm, round and painless sore or multiple sores, called chancres, appear, according to the CDC. Symptoms in the secondary stage can include skin rashes and/or sores, fever, sore throat, hair loss, headaches and weight loss.

“People who have ‘early’ syphilis infections can more easily spread the infection to their sex partners,” according to the CDC.

Symptoms from the secondary stage go away on their own, which is when the disease enters the latent stage. Without treatment, the disease can move to the late stages.

During any stage, syphilis can also invade the nervous system, according to the CDC. Syphilis is typically diagnosed following a blood test; Fredrick suggests people being tested soon after a possible infection also undergo testing later to avoid a possible false negative result.

Of the 694 new-onset cases in Clark County in 2015, 615 were reported among men, Fredrick said.

That’s consistent with national statistics, which showed 91 percent of new diagnoses in the United States in 2014 were among men. Of those 91 percent, 83 percent of cases affected men who had sex with other men.

Fredrick said unprotected sex and sex with multiple partners are believed to contribute to these comparatively high rates.

The Southern Nevada Health District’s statistics are just the latest to show high rates of syphilis in the Silver State.

Nevada had the highest rate of reported primary and secondary syphilis cases in the West in 2014, at a rate of 12.8 per 100,000 members of the population, the health district said.

Contact Pashtana Usufzy at pusufzy@reviewjournal.com or 702-380-4563. Find her on Twitter: @pashtana_u