Rates of both chlamydia and syphilis in Miami-Dade have nearly doubled since 2006, according to new statistics from the Florida Department of Health.

The rise in sexually transmitted diseases is an unsettling and largely unnoticed trend, said Alex Moreno, the clinical program manager for the adolescent medicine division at the University of Miami Miller School of Medicine.

“It’s all on our back burner,” Moreno said. “That’s the scary thing.”

There were 400 cases of chlamydia per 100,000 residents in 2013. In 2006, there were 200. Syphilis has similarly increased, jumping from 8.4 cases per 100,000 to over 16 in the same seven years, according to the health department numbers.

Chlamydia can cause fertility problems if left untreated. Syphilis causes sores and rashes and may lead to paralysis and, eventually, if untreated, even death.

Already, the Miami metropolitan statistical area had the highest rate of diagnosed HIV infections in the country in 2011, according to the latest data from the Centers for Disease Control.

Miami-Dade County has a slightly lower rate of chlamydia than the state as a whole, but a higher rate of syphilis. Statewide, the rate of chlamydia is 419 per 100,000 residents in 2013 and the rate of syphilis is 7.9 per 100,000 residents.

Younger people in Miami-Dade were generally more likely to have STDs, the numbers indicated. Since 2009, STDs in the 25-to-34 age range have increased by 5 percentage points.

And even though STDs in people under 25 have decreased by 8 percentage points, that same age group is significantly more likely than any other age group to have an STD, accounting for 56 percent of all cases of chlamydia, gonorrhea and syphilis in Miami-Dade in 2013, according to the statistics.

Chlamydia in particular is pushing the numbers up — 70 percent of all reported cases of chlamydia are among adults ages 15-24, according to the CDC.