Sexually transmitted infections are on the rise, putting more people at risk as they spread. Chlamydia rates have nearly doubled since 2000, while the rate of gonorrhea went up by 50% over the same period. The Centers for Disease Control and Prevention reports that syphilis rates are reaching levels last seen in the 1950s.
But some regions of the U.S. are seeing higher rates than others.
Stacker used CDC data to look at which counties reported the highest rate of sexually transmitted infections in Iowa. Counties are ranked by the rate of chlamydia infections, the most prominent STI at the national level, with gonorrhea and then syphilis rates serving as tiebreakers. This story focuses on bacterial infections, which can be cured, rather than viral infections such as HIV and herpes. At the county level, 2021 cases are the most recent available from the CDC, but state and national-level data for 2022 are also included. This story focuses on sexual transmissions and does not include congenital syphilis cases that were inherited from the mother.
Condoms are the most effective way to prevent the spread of STIs for people with multiple sexual partners, but research has found a decreasing rate of condom use among straight, bisexual, and gay male populations.
During the HIV/AIDS epidemic throughout the 1980s and 1990s, public health efforts advocating for condom use helped curb the spread of the virus. Today, however, condoms are no longer the only tool. Pills such as PrEP lower the risk of contracting HIV from sex by as much as 99%.
While more recent data is not available, the latest CDC survey from 2011-2015 showed less than half of unmarried men used condoms during the last time they had sex.
Among high school students having sex, the share using condoms has fallen from 60% in 2011 to 52% in 2021. While one-third of sexually active students used hormonal birth control, only 10% used both condoms and birth control. Methods like the pill and IUDs are effective at preventing pregnancy but do not stop the spread of STIs.
Chlamydia, gonorrhea, and syphilis are technically bacterial infections—meaning they can be cured with antibiotics—but they can still have lasting health impacts, including pelvic inflammatory disease and infertility. These risks are heightened when left untreated, which many STIs are as they don't obviously present themselves.
The CDC recommends annual testing for cisgender women, transgender men, and gender-nonconforming people with cervixes. It also recommends annual testing for males with male sexual partners. People in these groups who frequently have sex with anonymous partners should be tested every three to six months. Anyone with symptoms should always get tested according to the guidelines.
The CDC says there is little evidence that screening among straight men lowers the spread, and the agency's limited budget is put towards programs benefiting the most at-risk groups. However, some public health groups advocate for testing among all people regardless of sex and sexual orientation.
Data from the National Survey of Family Growth shows men on average have more opposite-sex sexual partners than women, and some argue that catching STIs throughout a sexual network rather than just for the most at-risk groups could curb their spread.
Soon, a pill may also help counter the spread of STIs. DoxyPEP can be taken 24 to 72 hours after unprotected sex and stops an STI before it becomes spreadable and symptomatic. The CDC has shared proposed guidelines recommending it for men who have sex with men and transgender women. The drug was originally approved for treating inhalation of anthrax, and doctors can prescribe it for off-label use.
Read on to see how STI infection rates in Iowa compare nationally, and the top counties.
You may also like: Most commonly hunted migratory birds in Iowa
Emma Rubin // Stacker
1 / 51State-level statistics
- Chlamydia cases: 457.2 per 100K (#30 nationally, 14,634 cases)
- Gonorrhea cases: 139.5 per 100K (#35 nationally, 4,466 cases)
- Primary and secondary syphilis cases: 10.4 per 100K (#40 nationally, 334 cases)
#50. Warren County
- Chlamydia cases: 286.5 per 100K people (153 cases)
- Gonorrhea cases: 112.4 per 100K people (60 cases)
- Syphilis cases (non-congenital): 16.9 per 100K people (9 cases)
--- Primary and secondary syphilis: 9.4 per 100K people (5 cases)
--- Nonprimary and nonsecondary early syphilis: 7.5 per 100K people (4 cases)
stivanderson // Shutterstock
3 / 51#49. Jefferson County
- Chlamydia cases: 287.6 per 100K people (45 cases)
- Gonorrhea cases: 115.0 per 100K people (18 cases)
- Syphilis cases (non-congenital): 0 cases
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 0 cases
Eddie J. Rodriquez // Shutterstock
4 / 51#48. Louisa County
- Chlamydia cases: 288.4 per 100K people (31 case)
- Gonorrhea cases: 130.2 per 100K people (14 cases)
- Syphilis cases (non-congenital): 0 cases
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 0 cases
#47. Plymouth County
- Chlamydia cases: 288.5 per 100K people (74 cases)
- Gonorrhea cases: 42.9 per 100K people (11 case)
- Syphilis cases (non-congenital): 15.6 per 100K people (4 cases)
--- Primary and secondary syphilis: 15.6 per 100K people (4 cases)
--- Nonprimary and nonsecondary early syphilis: 0 cases
You may also like: Coldest Novembers in Iowa since 1895
Mary Key // Shutterstock
6 / 51#46. Clarke County
- Chlamydia cases: 296.4 per 100K people (29 cases)
- Gonorrhea cases: 51.1 per 100K people (5 cases)
- Syphilis cases (non-congenital): 0 cases
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 0 cases
Jacob Boomsma // Shutterstock
7 / 51#45. Chickasaw County
- Chlamydia cases: 302.9 per 100K people (36 cases)
- Gonorrhea cases: 16.8 per 100K people (2 cases)
- Syphilis cases (non-congenital): 8.4 per 100K people (1 case)
--- Primary and secondary syphilis: 8.4 per 100K people (1 case)
--- Nonprimary and nonsecondary early syphilis: 0 cases
SevenMaps // Shutterstock
8 / 51#44. Benton County
- Chlamydia cases: 303.6 per 100K people (78 cases)
- Gonorrhea cases: 85.6 per 100K people (22 cases)
- Syphilis cases (non-congenital): 3.9 per 100K people (1 case)
--- Primary and secondary syphilis: 3.9 per 100K people (1 case)
--- Nonprimary and nonsecondary early syphilis: 0 cases
#43. Marion County
- Chlamydia cases: 305.6 per 100K people (102 cases)
- Gonorrhea cases: 86.9 per 100K people (29 cases)
- Syphilis cases (non-congenital): 12.0 per 100K people (4 cases)
--- Primary and secondary syphilis: 6.0 per 100K people (2 cases)
--- Nonprimary and nonsecondary early syphilis: 6.0 per 100K people (2 cases)
Brooke Van Zee // Shutterstock
10 / 51#42. Wayne County
- Chlamydia cases: 307.3 per 100K people (20 cases)
- Gonorrhea cases: 30.7 per 100K people (2 cases)
- Syphilis cases (non-congenital): 15.4 per 100K people (1 case)
--- Primary and secondary syphilis: 15.4 per 100K people (1 case)
--- Nonprimary and nonsecondary early syphilis: 0 cases
You may also like: Highest-rated Class of 2026 football recruits from Iowa
Joel McCartan // Shutterstock
11 / 51#41. O'brien County
- Chlamydia cases: 313.9 per 100K people (44 cases)
- Gonorrhea cases: 64.2 per 100K people (9 cases)
- Syphilis cases (non-congenital): 7.1 per 100K people (1 case)
--- Primary and secondary syphilis: 7.1 per 100K people (1 case)
--- Nonprimary and nonsecondary early syphilis: 0 cases
Doug Lambert // Shutterstock
12 / 51#40. Buchanan County
- Chlamydia cases: 314.7 per 100K people (65 cases)
- Gonorrhea cases: 77.5 per 100K people (16 cases)
- Syphilis cases (non-congenital): 0 cases
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 0 cases
Marsen // Shutterstock
13 / 51#39. Jones County
- Chlamydia cases: 317.2 per 100K people (66 cases)
- Gonorrhea cases: 52.9 per 100K people (11 case)
- Syphilis cases (non-congenital): 4.8 per 100K people (1 case)
--- Primary and secondary syphilis: 4.8 per 100K people (1 case)
--- Nonprimary and nonsecondary early syphilis: 0 cases
Kimberly's Impressions // Shutterstock
14 / 51#38. Taylor County
- Chlamydia cases: 323.8 per 100K people (19 cases)
- Gonorrhea cases: 34.1 per 100K people (2 cases)
- Syphilis cases (non-congenital): 0 cases
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 0 cases
#37. Pocahontas County
- Chlamydia cases: 325.1 per 100K people (23 cases)
- Gonorrhea cases: 84.8 per 100K people (6 cases)
- Syphilis cases (non-congenital): 0 cases
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 0 cases
You may also like: Hottest Februarys in Iowa since 1895
Eddie J. Rodriquez // Shutterstock
16 / 51#36. Clinton County
- Chlamydia cases: 327.1 per 100K people (152 cases)
- Gonorrhea cases: 144.2 per 100K people (67 cases)
- Syphilis cases (non-congenital): 19.4 per 100K people (9 cases)
--- Primary and secondary syphilis: 10.8 per 100K people (5 cases)
--- Nonprimary and nonsecondary early syphilis: 8.6 per 100K people (4 cases)
#35. Winnebago County
- Chlamydia cases: 328.5 per 100K people (35 cases)
- Gonorrhea cases: 75.1 per 100K people (8 cases)
- Syphilis cases (non-congenital): 9.4 per 100K people (1 case)
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 9.4 per 100K people (1 case)
#34. Monroe County
- Chlamydia cases: 328.5 per 100K people (25 cases)
- Gonorrhea cases: 78.8 per 100K people (6 cases)
- Syphilis cases (non-congenital): 0 cases
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 0 cases
Jacob Boomsma // Shutterstock
19 / 51#33. Dallas County
- Chlamydia cases: 328.5 per 100K people (341 case)
- Gonorrhea cases: 135.8 per 100K people (141 case)
- Syphilis cases (non-congenital): 11.6 per 100K people (12 cases)
--- Primary and secondary syphilis: 5.8 per 100K people (6 cases)
--- Nonprimary and nonsecondary early syphilis: 5.8 per 100K people (6 cases)
SevenMaps // Shutterstock
20 / 51#32. Montgomery County
- Chlamydia cases: 339.1 per 100K people (35 cases)
- Gonorrhea cases: 48.4 per 100K people (5 cases)
- Syphilis cases (non-congenital): 9.7 per 100K people (1 case)
--- Primary and secondary syphilis: 9.7 per 100K people (1 case)
--- Nonprimary and nonsecondary early syphilis: 0 cases
You may also like: In search of affordability: How Iowa ranks for cost of living
#31. Wright County
- Chlamydia cases: 344.2 per 100K people (44 cases)
- Gonorrhea cases: 39.1 per 100K people (5 cases)
- Syphilis cases (non-congenital): 15.6 per 100K people (2 cases)
--- Primary and secondary syphilis: 7.8 per 100K people (1 case)
--- Nonprimary and nonsecondary early syphilis: 7.8 per 100K people (1 case)
#30. Lee County
- Chlamydia cases: 346.2 per 100K people (115 cases)
- Gonorrhea cases: 195.7 per 100K people (65 cases)
- Syphilis cases (non-congenital): 0 cases
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 0 cases
Jonathan Park // Shutterstock
23 / 51#29. Cherokee County
- Chlamydia cases: 347.7 per 100K people (40 cases)
- Gonorrhea cases: 86.9 per 100K people (10 cases)
- Syphilis cases (non-congenital): 0 cases
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 0 cases
Kelsey Haugen // Shutterstock
24 / 51#28. Union County
- Chlamydia cases: 349.5 per 100K people (42 cases)
- Gonorrhea cases: 83.2 per 100K people (10 cases)
- Syphilis cases (non-congenital): 0 cases
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 0 cases
#27. Mahaska County
- Chlamydia cases: 359.4 per 100K people (79 cases)
- Gonorrhea cases: 150.1 per 100K people (33 cases)
- Syphilis cases (non-congenital): 9.1 per 100K people (2 cases)
--- Primary and secondary syphilis: 4.5 per 100K people (1 case)
--- Nonprimary and nonsecondary early syphilis: 4.5 per 100K people (1 case)
You may also like: Counties with the most veterans in Iowa
#26. Keokuk County
- Chlamydia cases: 363.1 per 100K people (36 cases)
- Gonorrhea cases: 121.0 per 100K people (12 cases)
- Syphilis cases (non-congenital): 10.1 per 100K people (1 case)
--- Primary and secondary syphilis: 10.1 per 100K people (1 case)
--- Nonprimary and nonsecondary early syphilis: 0 cases
Life Atlas Photography // Shutterstock
27 / 51#25. Ringgold County
- Chlamydia cases: 366.5 per 100K people (17 cases)
- Gonorrhea cases: 43.1 per 100K people (2 cases)
- Syphilis cases (non-congenital): 0 cases
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 0 cases
Kuehner // Shutterstock
28 / 51#24. Fayette County
- Chlamydia cases: 368.7 per 100K people (71 case)
- Gonorrhea cases: 119.4 per 100K people (23 cases)
- Syphilis cases (non-congenital): 5.2 per 100K people (1 case)
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 5.2 per 100K people (1 case)
#23. Cerro Gordo County
- Chlamydia cases: 379.3 per 100K people (162 cases)
- Gonorrhea cases: 201.4 per 100K people (86 cases)
- Syphilis cases (non-congenital): 11.7 per 100K people (5 cases)
--- Primary and secondary syphilis: 7.0 per 100K people (3 cases)
--- Nonprimary and nonsecondary early syphilis: 4.7 per 100K people (2 cases)
#22. Hamilton County
- Chlamydia cases: 389.6 per 100K people (58 cases)
- Gonorrhea cases: 100.8 per 100K people (15 cases)
- Syphilis cases (non-congenital): 0 cases
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 0 cases
You may also like: See the most extreme temperatures in Iowa history
PICTOR PICTURES // Shutterstock
31 / 51#21. Henry County
- Chlamydia cases: 397.3 per 100K people (81 case)
- Gonorrhea cases: 181.5 per 100K people (37 cases)
- Syphilis cases (non-congenital): 19.6 per 100K people (4 cases)
--- Primary and secondary syphilis: 14.7 per 100K people (3 cases)
--- Nonprimary and nonsecondary early syphilis: 4.9 per 100K people (1 case)
SevenMaps // Shutterstock
32 / 51#20. Hardin County
- Chlamydia cases: 413.0 per 100K people (69 cases)
- Gonorrhea cases: 137.7 per 100K people (23 cases)
- Syphilis cases (non-congenital): 0 cases
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 0 cases
#19. Crawford County
- Chlamydia cases: 444.6 per 100K people (72 cases)
- Gonorrhea cases: 61.8 per 100K people (10 cases)
- Syphilis cases (non-congenital): 12.4 per 100K people (2 cases)
--- Primary and secondary syphilis: 12.4 per 100K people (2 cases)
--- Nonprimary and nonsecondary early syphilis: 0 cases
Lucas Oglesbee // Shutterstock
34 / 51#18. Tama County
- Chlamydia cases: 444.7 per 100K people (75 cases)
- Gonorrhea cases: 213.4 per 100K people (36 cases)
- Syphilis cases (non-congenital): 5.9 per 100K people (1 case)
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 5.9 per 100K people (1 case)
Naw Eh Wah // Shutterstock
35 / 51#17. Buena Vista County
- Chlamydia cases: 462.2 per 100K people (96 cases)
- Gonorrhea cases: 67.4 per 100K people (14 cases)
- Syphilis cases (non-congenital): 4.8 per 100K people (1 case)
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 4.8 per 100K people (1 case)
You may also like: Cities with the most expensive homes in Iowa
#16. Muscatine County
- Chlamydia cases: 487.3 per 100K people (208 cases)
- Gonorrhea cases: 105.4 per 100K people (45 cases)
- Syphilis cases (non-congenital): 9.4 per 100K people (4 cases)
--- Primary and secondary syphilis: 7.0 per 100K people (3 cases)
--- Nonprimary and nonsecondary early syphilis: 2.3 per 100K people (1 case)
SevenMaps // Shutterstock
37 / 51#15. Franklin County
- Chlamydia cases: 502.4 per 100K people (50 cases)
- Gonorrhea cases: 160.8 per 100K people (16 cases)
- Syphilis cases (non-congenital): 10.0 per 100K people (1 case)
--- Primary and secondary syphilis: 10.0 per 100K people (1 case)
--- Nonprimary and nonsecondary early syphilis: 0 cases
#14. Dubuque County
- Chlamydia cases: 516.6 per 100K people (510 cases)
- Gonorrhea cases: 243.1 per 100K people (240 cases)
- Syphilis cases (non-congenital): 12.2 per 100K people (12 cases)
--- Primary and secondary syphilis: 6.1 per 100K people (6 cases)
--- Nonprimary and nonsecondary early syphilis: 6.1 per 100K people (6 cases)
#13. Pottawattamie County
- Chlamydia cases: 521.9 per 100K people (487 cases)
- Gonorrhea cases: 225.1 per 100K people (210 cases)
- Syphilis cases (non-congenital): 31.1 per 100K people (29 cases)
--- Primary and secondary syphilis: 21.4 per 100K people (20 cases)
--- Nonprimary and nonsecondary early syphilis: 9.6 per 100K people (9 cases)
#12. Linn County
- Chlamydia cases: 546.4 per 100K people (1,251 case)
- Gonorrhea cases: 169.9 per 100K people (389 cases)
- Syphilis cases (non-congenital): 9.6 per 100K people (22 cases)
--- Primary and secondary syphilis: 4.8 per 100K people (11 case)
--- Nonprimary and nonsecondary early syphilis: 4.8 per 100K people (11 case)
You may also like: Movies and TV shows casting in Iowa
#11. Marshall County
- Chlamydia cases: 549.5 per 100K people (219 cases)
- Gonorrhea cases: 173.1 per 100K people (69 cases)
- Syphilis cases (non-congenital): 5.0 per 100K people (2 cases)
--- Primary and secondary syphilis: 2.5 per 100K people (1 case)
--- Nonprimary and nonsecondary early syphilis: 2.5 per 100K people (1 case)
#10. Appanoose County
- Chlamydia cases: 603.7 per 100K people (74 cases)
- Gonorrhea cases: 244.8 per 100K people (30 cases)
- Syphilis cases (non-congenital): 8.2 per 100K people (1 case)
--- Primary and secondary syphilis: 8.2 per 100K people (1 case)
--- Nonprimary and nonsecondary early syphilis: 0 cases
#9. Scott County
- Chlamydia cases: 614.3 per 100K people (1,070 cases)
- Gonorrhea cases: 339.9 per 100K people (592 cases)
- Syphilis cases (non-congenital): 14.4 per 100K people (25 cases)
--- Primary and secondary syphilis: 10.3 per 100K people (18 cases)
--- Nonprimary and nonsecondary early syphilis: 4.0 per 100K people (7 cases)
#8. Johnson County
- Chlamydia cases: 665.6 per 100K people (1,030 cases)
- Gonorrhea cases: 145.4 per 100K people (225 cases)
- Syphilis cases (non-congenital): 34.9 per 100K people (54 cases)
--- Primary and secondary syphilis: 22.0 per 100K people (34 cases)
--- Nonprimary and nonsecondary early syphilis: 12.9 per 100K people (20 cases)
#7. Polk County
- Chlamydia cases: 668.8 per 100K people (3,323 cases)
- Gonorrhea cases: 381.4 per 100K people (1,895 cases)
- Syphilis cases (non-congenital): 43.7 per 100K people (217 cases)
--- Primary and secondary syphilis: 24.8 per 100K people (123 cases)
--- Nonprimary and nonsecondary early syphilis: 18.9 per 100K people (94 cases)
You may also like: Coldest Februarys in Iowa since 1895
#6. Webster County
- Chlamydia cases: 678.4 per 100K people (252 cases)
- Gonorrhea cases: 371.5 per 100K people (138 cases)
- Syphilis cases (non-congenital): 5.4 per 100K people (2 cases)
--- Primary and secondary syphilis: 2.7 per 100K people (1 case)
--- Nonprimary and nonsecondary early syphilis: 2.7 per 100K people (1 case)
#5. Story County
- Chlamydia cases: 685.6 per 100K people (682 cases)
- Gonorrhea cases: 139.7 per 100K people (139 cases)
- Syphilis cases (non-congenital): 16.1 per 100K people (16 cases)
--- Primary and secondary syphilis: 8.0 per 100K people (8 cases)
--- Nonprimary and nonsecondary early syphilis: 8.0 per 100K people (8 cases)
#4. Wapello County
- Chlamydia cases: 692.1 per 100K people (244 cases)
- Gonorrhea cases: 269.5 per 100K people (95 cases)
- Syphilis cases (non-congenital): 5.7 per 100K people (2 cases)
--- Primary and secondary syphilis: 2.8 per 100K people (1 case)
--- Nonprimary and nonsecondary early syphilis: 2.8 per 100K people (1 case)
Eddie J. Rodriquez // Shutterstock
49 / 51#3. Des Moines County
- Chlamydia cases: 745.6 per 100K people (287 cases)
- Gonorrhea cases: 394.9 per 100K people (152 cases)
- Syphilis cases (non-congenital): 7.8 per 100K people (3 cases)
--- Primary and secondary syphilis: 5.2 per 100K people (2 cases)
--- Nonprimary and nonsecondary early syphilis: 2.6 per 100K people (1 case)
#2. Woodbury County
- Chlamydia cases: 778.4 per 100K people (822 cases)
- Gonorrhea cases: 403.4 per 100K people (426 cases)
- Syphilis cases (non-congenital): 23.7 per 100K people (25 cases)
--- Primary and secondary syphilis: 14.2 per 100K people (15 cases)
--- Nonprimary and nonsecondary early syphilis: 9.5 per 100K people (10 cases)
You may also like: Biggest sources of immigrants to Iowa
#1. Black Hawk County
- Chlamydia cases: 845.3 per 100K people (1,102 cases)
- Gonorrhea cases: 396.6 per 100K people (517 cases)
- Syphilis cases (non-congenital): 26.1 per 100K people (34 cases)
--- Primary and secondary syphilis: 16.9 per 100K people (22 cases)
--- Nonprimary and nonsecondary early syphilis: 9.2 per 100K people (12 cases)
This story features data reporting and writing by Emma Rubin and is part of a series utilizing data automation across 49 states.
