King County saw the number of syphilis, gonorrhea, and chlamydia cases rise from 2015-16, according to a report from Seattle & King County Public Health.

Syphilis and chlamydia cases each grew 11 percent over the one-year period, and gonorrhea cases went up 15 percent.

The number of syphilis cases doubled among women, but it increased among men too. Gonorrhea cases went up mostly among men who have sex with men, and chlamydia went up among both men and women.

There are a lot of reasons why the rates would spike.

Public health officials cautioned that the some of the new cases could be due to increased testing and diagnosis, but they do believe more people are getting infected.

Officials suspect that the prevalence of anti-viral drugs that help prevent HIV could mean people are engaging in riskier sex, which could lead to the spread of sexually transmitted diseases. Rising injection drug use could be an explanation for the increase in syphilis cases. The rise in chlamydia could be caused by a decrease in public health prevention resources, according to Seattle & King County Public Health.

The King County data follows state and national trends. National syphilis rates increased 18 percent from 2015-16, according to data that was released last month from the Centers for Disease Control and Prevention.

Syphilis, gonorrhea, and chlamydia are all treatable with antibiotics. However, they can lead to dangerous health outcomes if left untreated.