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 Pennsylvania. 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 Pennsylvania compare nationally, and the top counties.
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Emma Rubin // Stacker
1 / 51State-level statistics
- Chlamydia cases: 421.3 per 100K (#34 nationally, 54,645 cases)
- Gonorrhea cases: 145.3 per 100K (#32 nationally, 18,851 cases)
- Primary and secondary syphilis cases: 10.8 per 100K (#39 nationally, 1,397 cases)
#50. Wyoming County
- Chlamydia cases: 157.5 per 100K people (41 case)
- Gonorrhea cases: 26.9 per 100K people (7 cases)
- Syphilis cases (non-congenital): 0 cases
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 0 cases
#49. Elk County
- Chlamydia cases: 175.4 per 100K people (54 cases)
- Gonorrhea cases: 6.5 per 100K people (2 cases)
- Syphilis cases (non-congenital): 0 cases
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 0 cases
Sabrina Janelle Gordon // Shutterstock
4 / 51#48. Butler County
- Chlamydia cases: 183.2 per 100K people (356 cases)
- Gonorrhea cases: 40.1 per 100K people (78 cases)
- Syphilis cases (non-congenital): 5.7 per 100K people (11 case)
--- Primary and secondary syphilis: 3.6 per 100K people (7 cases)
--- Nonprimary and nonsecondary early syphilis: 2.1 per 100K people (4 cases)
#47. Union County
- Chlamydia cases: 192.6 per 100K people (82 cases)
- Gonorrhea cases: 18.8 per 100K people (8 cases)
- Syphilis cases (non-congenital): 7.0 per 100K people (3 cases)
--- Primary and secondary syphilis: 7.0 per 100K people (3 cases)
--- Nonprimary and nonsecondary early syphilis: 0 cases
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#46. Carbon County
- Chlamydia cases: 192.6 per 100K people (126 cases)
- Gonorrhea cases: 56.6 per 100K people (37 cases)
- Syphilis cases (non-congenital): 0 cases
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 0 cases
#45. Crawford County
- Chlamydia cases: 193.2 per 100K people (161 case)
- Gonorrhea cases: 56.4 per 100K people (47 cases)
- Syphilis cases (non-congenital): 3.6 per 100K people (3 cases)
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 3.6 per 100K people (3 cases)
#44. Westmoreland County
- Chlamydia cases: 195.7 per 100K people (691 case)
- Gonorrhea cases: 48.4 per 100K people (171 case)
- Syphilis cases (non-congenital): 3.4 per 100K people (12 cases)
--- Primary and secondary syphilis: 1.1 per 100K people (4 cases)
--- Nonprimary and nonsecondary early syphilis: 2.3 per 100K people (8 cases)
Alejandro Guzmani // Shutterstock
9 / 51#43. Fulton County
- Chlamydia cases: 199.7 per 100K people (29 cases)
- Gonorrhea cases: 20.7 per 100K people (3 cases)
- Syphilis cases (non-congenital): 0 cases
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 0 cases
#42. Adams County
- Chlamydia cases: 201.7 per 100K people (210 cases)
- Gonorrhea cases: 45.1 per 100K people (47 cases)
- Syphilis cases (non-congenital): 1.9 per 100K people (2 cases)
--- Primary and secondary syphilis: 1.0 per 100K people (1 case)
--- Nonprimary and nonsecondary early syphilis: 1.0 per 100K people (1 case)
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eric scott gillin // Shutterstock
11 / 51#41. Cameron County
- Chlamydia cases: 201.8 per 100K people (9 cases)
- Gonorrhea cases: 44.9 per 100K people (2 cases)
- Syphilis cases (non-congenital): 0 cases
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 0 cases
LittleKitty // Shutterstock
12 / 51#40. Chester County
- Chlamydia cases: 202.7 per 100K people (1,092 cases)
- Gonorrhea cases: 45.5 per 100K people (245 cases)
- Syphilis cases (non-congenital): 11.3 per 100K people (61 case)
--- Primary and secondary syphilis: 6.3 per 100K people (34 cases)
--- Nonprimary and nonsecondary early syphilis: 5.0 per 100K people (27 cases)
#39. Mckean County
- Chlamydia cases: 202.8 per 100K people (81 case)
- Gonorrhea cases: 70.1 per 100K people (28 cases)
- Syphilis cases (non-congenital): 0 cases
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 0 cases
George Sheldon // Shutterstock
14 / 51#38. Mifflin County
- Chlamydia cases: 203.7 per 100K people (94 cases)
- Gonorrhea cases: 6.5 per 100K people (3 cases)
- Syphilis cases (non-congenital): 6.5 per 100K people (3 cases)
--- Primary and secondary syphilis: 6.5 per 100K people (3 cases)
--- Nonprimary and nonsecondary early syphilis: 0 cases
#37. Clarion County
- Chlamydia cases: 207.2 per 100K people (77 cases)
- Gonorrhea cases: 21.5 per 100K people (8 cases)
- Syphilis cases (non-congenital): 0 cases
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 0 cases
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#36. Clinton County
- Chlamydia cases: 208.2 per 100K people (78 cases)
- Gonorrhea cases: 37.4 per 100K people (14 cases)
- Syphilis cases (non-congenital): 5.3 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)
#35. Bradford County
- Chlamydia cases: 213.7 per 100K people (128 cases)
- Gonorrhea cases: 36.7 per 100K people (22 cases)
- Syphilis cases (non-congenital): 0 cases
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 0 cases
#34. Bucks County
- Chlamydia cases: 214.2 per 100K people (1,384 cases)
- Gonorrhea cases: 51.5 per 100K people (333 cases)
- Syphilis cases (non-congenital): 13.5 per 100K people (87 cases)
--- Primary and secondary syphilis: 6.5 per 100K people (42 cases)
--- Nonprimary and nonsecondary early syphilis: 7.0 per 100K people (45 cases)
#33. Washington County
- Chlamydia cases: 217.2 per 100K people (455 cases)
- Gonorrhea cases: 69.7 per 100K people (146 cases)
- Syphilis cases (non-congenital): 3.3 per 100K people (7 cases)
--- Primary and secondary syphilis: 1.0 per 100K people (2 cases)
--- Nonprimary and nonsecondary early syphilis: 2.4 per 100K people (5 cases)
#32. Montgomery County
- Chlamydia cases: 223.7 per 100K people (1,925 cases)
- Gonorrhea cases: 64.1 per 100K people (552 cases)
- Syphilis cases (non-congenital): 6.3 per 100K people (54 cases)
--- Primary and secondary syphilis: 2.8 per 100K people (24 cases)
--- Nonprimary and nonsecondary early syphilis: 3.5 per 100K people (30 cases)
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#31. Cambria County
- Chlamydia cases: 242.1 per 100K people (320 cases)
- Gonorrhea cases: 65.1 per 100K people (86 cases)
- Syphilis cases (non-congenital): 4.5 per 100K people (6 cases)
--- Primary and secondary syphilis: 4.5 per 100K people (6 cases)
--- Nonprimary and nonsecondary early syphilis: 0 cases
#30. Northumberland County
- Chlamydia cases: 246.5 per 100K people (225 cases)
- Gonorrhea cases: 35.1 per 100K people (32 cases)
- Syphilis cases (non-congenital): 8.8 per 100K people (8 cases)
--- Primary and secondary syphilis: 7.7 per 100K people (7 cases)
--- Nonprimary and nonsecondary early syphilis: 1.1 per 100K people (1 case)
#29. Lancaster County
- Chlamydia cases: 247.3 per 100K people (1,369 cases)
- Gonorrhea cases: 62.1 per 100K people (344 cases)
- Syphilis cases (non-congenital): 15.9 per 100K people (88 cases)
--- Primary and secondary syphilis: 10.5 per 100K people (58 cases)
--- Nonprimary and nonsecondary early syphilis: 5.4 per 100K people (30 cases)
Scenic Corner // Shutterstock
24 / 51#28. Montour County
- Chlamydia cases: 248.8 per 100K people (45 cases)
- Gonorrhea cases: 38.7 per 100K people (7 cases)
- Syphilis cases (non-congenital): 27.6 per 100K people (5 cases)
--- Primary and secondary syphilis: 11.1 per 100K people (2 cases)
--- Nonprimary and nonsecondary early syphilis: 16.6 per 100K people (3 cases)
#27. Huntingdon County
- Chlamydia cases: 259.7 per 100K people (114 cases)
- Gonorrhea cases: 31.9 per 100K people (14 cases)
- Syphilis cases (non-congenital): 4.6 per 100K people (2 cases)
--- Primary and secondary syphilis: 4.6 per 100K people (2 cases)
--- Nonprimary and nonsecondary early syphilis: 0 cases
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Bennekom // Shutterstock
26 / 51#26. Schuylkill County
- Chlamydia cases: 264.5 per 100K people (379 cases)
- Gonorrhea cases: 66.3 per 100K people (95 cases)
- Syphilis cases (non-congenital): 16.8 per 100K people (24 cases)
--- Primary and secondary syphilis: 9.8 per 100K people (14 cases)
--- Nonprimary and nonsecondary early syphilis: 7.0 per 100K people (10 cases)
#25. Cumberland County
- Chlamydia cases: 267.0 per 100K people (702 cases)
- Gonorrhea cases: 69.6 per 100K people (183 cases)
- Syphilis cases (non-congenital): 8.0 per 100K people (21 case)
--- Primary and secondary syphilis: 5.7 per 100K people (15 cases)
--- Nonprimary and nonsecondary early syphilis: 2.3 per 100K people (6 cases)
#24. Venango County
- Chlamydia cases: 270.3 per 100K people (135 cases)
- Gonorrhea cases: 28.0 per 100K people (14 cases)
- Syphilis cases (non-congenital): 0 cases
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 0 cases
#23. Lackawanna County
- Chlamydia cases: 270.3 per 100K people (583 cases)
- Gonorrhea cases: 88.1 per 100K people (190 cases)
- Syphilis cases (non-congenital): 8.8 per 100K people (19 cases)
--- Primary and secondary syphilis: 2.3 per 100K people (5 cases)
--- Nonprimary and nonsecondary early syphilis: 6.5 per 100K people (14 cases)
#22. Lebanon County
- Chlamydia cases: 288.5 per 100K people (414 cases)
- Gonorrhea cases: 39.0 per 100K people (56 cases)
- Syphilis cases (non-congenital): 8.4 per 100K people (12 cases)
--- Primary and secondary syphilis: 5.6 per 100K people (8 cases)
--- Nonprimary and nonsecondary early syphilis: 2.8 per 100K people (4 cases)
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#21. Blair County
- Chlamydia cases: 296.5 per 100K people (361 case)
- Gonorrhea cases: 40.2 per 100K people (49 cases)
- Syphilis cases (non-congenital): 2.5 per 100K people (3 cases)
--- Primary and secondary syphilis: 0 cases
--- Nonprimary and nonsecondary early syphilis: 2.5 per 100K people (3 cases)
Mark Rust // Shutterstock
32 / 51#20. Indiana County
- Chlamydia cases: 301.6 per 100K people (250 cases)
- Gonorrhea cases: 47.1 per 100K people (39 cases)
- Syphilis cases (non-congenital): 7.2 per 100K people (6 cases)
--- Primary and secondary syphilis: 2.4 per 100K people (2 cases)
--- Nonprimary and nonsecondary early syphilis: 4.8 per 100K people (4 cases)
Orlowski Designs LLC // Shutterstock
33 / 51#19. Beaver County
- Chlamydia cases: 304.9 per 100K people (508 cases)
- Gonorrhea cases: 97.2 per 100K people (162 cases)
- Syphilis cases (non-congenital): 7.8 per 100K people (13 cases)
--- Primary and secondary syphilis: 4.8 per 100K people (8 cases)
--- Nonprimary and nonsecondary early syphilis: 3.0 per 100K people (5 cases)
#18. Franklin County
- Chlamydia cases: 323.8 per 100K people (506 cases)
- Gonorrhea cases: 73.6 per 100K people (115 cases)
- Syphilis cases (non-congenital): 8.3 per 100K people (13 cases)
--- Primary and secondary syphilis: 5.1 per 100K people (8 cases)
--- Nonprimary and nonsecondary early syphilis: 3.2 per 100K people (5 cases)
#17. Columbia County
- Chlamydia cases: 328.3 per 100K people (213 cases)
- Gonorrhea cases: 44.7 per 100K people (29 cases)
- Syphilis cases (non-congenital): 4.6 per 100K people (3 cases)
--- Primary and secondary syphilis: 3.1 per 100K people (2 cases)
--- Nonprimary and nonsecondary early syphilis: 1.5 per 100K people (1 case)
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#16. Northampton County
- Chlamydia cases: 331.6 per 100K people (1,040 cases)
- Gonorrhea cases: 97.9 per 100K people (307 cases)
- Syphilis cases (non-congenital): 13.4 per 100K people (42 cases)
--- Primary and secondary syphilis: 4.8 per 100K people (15 cases)
--- Nonprimary and nonsecondary early syphilis: 8.6 per 100K people (27 cases)
#15. Fayette County
- Chlamydia cases: 334.0 per 100K people (424 cases)
- Gonorrhea cases: 86.7 per 100K people (110 cases)
- Syphilis cases (non-congenital): 10.2 per 100K people (13 cases)
--- Primary and secondary syphilis: 5.5 per 100K people (7 cases)
--- Nonprimary and nonsecondary early syphilis: 4.7 per 100K people (6 cases)
The American Explorer // Shutterstock
38 / 51#14. Lawrence County
- Chlamydia cases: 350.9 per 100K people (300 cases)
- Gonorrhea cases: 94.7 per 100K people (81 case)
- Syphilis cases (non-congenital): 4.7 per 100K people (4 cases)
--- Primary and secondary syphilis: 2.3 per 100K people (2 cases)
--- Nonprimary and nonsecondary early syphilis: 2.3 per 100K people (2 cases)
#13. Centre County
- Chlamydia cases: 353.0 per 100K people (556 cases)
- Gonorrhea cases: 38.1 per 100K people (60 cases)
- Syphilis cases (non-congenital): 7.6 per 100K people (12 cases)
--- Primary and secondary syphilis: 3.8 per 100K people (6 cases)
--- Nonprimary and nonsecondary early syphilis: 3.8 per 100K people (6 cases)
#12. Monroe County
- Chlamydia cases: 354.5 per 100K people (600 cases)
- Gonorrhea cases: 94.5 per 100K people (160 cases)
- Syphilis cases (non-congenital): 9.5 per 100K people (16 cases)
--- Primary and secondary syphilis: 4.1 per 100K people (7 cases)
--- Nonprimary and nonsecondary early syphilis: 5.3 per 100K people (9 cases)
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#11. York County
- Chlamydia cases: 356.7 per 100K people (1,636 cases)
- Gonorrhea cases: 120.8 per 100K people (554 cases)
- Syphilis cases (non-congenital): 10.0 per 100K people (46 cases)
--- Primary and secondary syphilis: 6.3 per 100K people (29 cases)
--- Nonprimary and nonsecondary early syphilis: 3.7 per 100K people (17 cases)
#10. Mercer County
- Chlamydia cases: 368.3 per 100K people (405 cases)
- Gonorrhea cases: 147.3 per 100K people (162 cases)
- Syphilis cases (non-congenital): 4.5 per 100K people (5 cases)
--- Primary and secondary syphilis: 3.6 per 100K people (4 cases)
--- Nonprimary and nonsecondary early syphilis: .9 per 100K people (1 case)
George Sheldon // Shutterstock
43 / 51#9. Lycoming County
- Chlamydia cases: 380.3 per 100K people (432 cases)
- Gonorrhea cases: 147.0 per 100K people (167 cases)
- Syphilis cases (non-congenital): 6.2 per 100K people (7 cases)
--- Primary and secondary syphilis: 3.5 per 100K people (4 cases)
--- Nonprimary and nonsecondary early syphilis: 2.6 per 100K people (3 cases)
#8. Luzerne County
- Chlamydia cases: 392.0 per 100K people (1,278 cases)
- Gonorrhea cases: 104.0 per 100K people (339 cases)
- Syphilis cases (non-congenital): 11.7 per 100K people (38 cases)
--- Primary and secondary syphilis: 8.9 per 100K people (29 cases)
--- Nonprimary and nonsecondary early syphilis: 2.8 per 100K people (9 cases)
#7. Erie County
- Chlamydia cases: 440.1 per 100K people (1,184 cases)
- Gonorrhea cases: 259.5 per 100K people (698 cases)
- Syphilis cases (non-congenital): 17.8 per 100K people (48 cases)
--- Primary and secondary syphilis: 9.7 per 100K people (26 cases)
--- Nonprimary and nonsecondary early syphilis: 8.2 per 100K people (22 cases)
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ESB Professional // Shutterstock
46 / 51#6. Allegheny County
- Chlamydia cases: 461.8 per 100K people (5,717 cases)
- Gonorrhea cases: 193.8 per 100K people (2,399 cases)
- Syphilis cases (non-congenital): 27.4 per 100K people (339 cases)
--- Primary and secondary syphilis: 11.2 per 100K people (139 cases)
--- Nonprimary and nonsecondary early syphilis: 16.2 per 100K people (200 cases)
#5. Lehigh County
- Chlamydia cases: 467.3 per 100K people (1,755 cases)
- Gonorrhea cases: 133.7 per 100K people (502 cases)
- Syphilis cases (non-congenital): 14.9 per 100K people (56 cases)
--- Primary and secondary syphilis: 6.1 per 100K people (23 cases)
--- Nonprimary and nonsecondary early syphilis: 8.8 per 100K people (33 cases)
#4. Berks County
- Chlamydia cases: 468.4 per 100K people (2,011 case)
- Gonorrhea cases: 96.2 per 100K people (413 cases)
- Syphilis cases (non-congenital): 17.2 per 100K people (74 cases)
--- Primary and secondary syphilis: 8.2 per 100K people (35 cases)
--- Nonprimary and nonsecondary early syphilis: 9.1 per 100K people (39 cases)
#3. Delaware County
- Chlamydia cases: 478.9 per 100K people (2,748 cases)
- Gonorrhea cases: 186.3 per 100K people (1,069 cases)
- Syphilis cases (non-congenital): 32.6 per 100K people (187 cases)
--- Primary and secondary syphilis: 12.9 per 100K people (74 cases)
--- Nonprimary and nonsecondary early syphilis: 19.7 per 100K people (113 cases)
#2. Dauphin County
- Chlamydia cases: 617.6 per 100K people (1,775 cases)
- Gonorrhea cases: 267.6 per 100K people (769 cases)
- Syphilis cases (non-congenital): 30.3 per 100K people (87 cases)
--- Primary and secondary syphilis: 17.0 per 100K people (49 cases)
--- Nonprimary and nonsecondary early syphilis: 13.2 per 100K people (38 cases)
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#1. Philadelphia County
- Chlamydia cases: 1,089.0 per 100K people (17,165 cases)
- Gonorrhea cases: 496.4 per 100K people (7,824 cases)
- Syphilis cases (non-congenital): 83.4 per 100K people (1,315 cases)
--- Primary and secondary syphilis: 37.2 per 100K people (586 cases)
--- Nonprimary and nonsecondary early syphilis: 46.2 per 100K people (729 cases)
This story features data reporting and writing by Emma Rubin and is part of a series utilizing data automation across 49 states.
