Sexually transmitted infections (STIs) are very common and costly to the nation’s health and economy.

A CDC analysis provides the clearest picture to date of STIs in the United States. CDC estimates indicate about 20 percent of the U.S. population – approximately one in five people in the U.S. – had an STI on any given day in 2018, and STIs acquired that year will cost the American healthcare system nearly $16 billion in healthcare costs alone. 

The analysis included eight common STIs: chlamydia, gonorrhea, hepatitis B virus (HBV), herpes simplex virus type 2 (HSV-2), human immunodeficiency virus (HIV), human papillomavirus (HPV), syphilis, and trichomoniasis. Chlamydia, trichomoniasis, genital herpes, and HPV accounted for 98% of all prevalent STIs and 93% of all new STIs in 2018.  

Given the serious health consequences of untreated STIs, and that many infections go undetected and unreported to CDC, these estimates are critical to better understanding the vast scope of the STI epidemic and who is most affected.

STI Overview: One in five people in the U.S. have an STI totaling nearly 68 million STIs in 2018. There were 26 million new STIs in 2018; almost half of new STIs were among youth aged 15-24 in the U.S. New STIs total nearly $16 billion in direct medical costs.

Estimated New and Existing STIs.

STI Prevalence and Incidence in the U.S.

What’s the difference? Prevalence versus incidence. Prevalence is the estimated number of infections – new or existing – in a given time. Incidence is the estimated number of new infections – diagnosed or undiagnosed. 

In 2018, the STI prevalence and incidence in the U.S. for eight STIs were as follows: HPV prevalence was 42.5 million, incidence 13 million; HSV-2 prevalence was 18.6 million, incidence 572,000; trichomoniasis prevalence was 2.6 million, incidence 6.9 million; chlamydia prevalence was 2.4 million, incidence 4 million; HIV (ages 13 and older) prevalence was 984,000, incidence 32,000; gonorrhea prevalence was 209,000, incidence 1.6 million; syphilis (ages 14 and older) prevalence was 156,000, incidence 146,000; and HBV (ages unavailable) prevalence was 103,000, incidence 8,300. Prevalence and incidence estimates are for adults and adolescents ages 15+ unless otherwise stated. The HIV and HBV data only represent sexually acquired infections.

STI Cost Estimates

STIs cost the U.S. healthcare system billions each year. In 2018, the new infections totaled nearly $16 billion in direct lifetime medical costs alone. The total cost of STIs far exceeds the medical cost burden estimated in this study, which did not include costs associated with lost productivity, other non-medical costs, and STI prevention.

In 2018 of the nearly $16 billion in direct medical costs, 26% of the total costs were among youth aged 15-24 while 25% of total costs were among women (these two groups were not mutually exclusive). Direct medical costs attributed to chlamydia, gonorrhea, and syphilis—all common, preventable infections—were $1.1 billion of the total cost. Direct medical costs for each of the eight STIs are as follows: HBV cost $45 million; HSV-2 cost $91 million; trichomoniasis cost $144 million; syphilis cost $174 million; gonorrhea cost $271 million; chlamydia cost $691 million; HPV cost $755 million; and HIV cost $13.7 billion.

More Data, Better Data Still Needed

CDC’s new estimates are based on modeling approaches that are more rigorous, robust, and comprehensive than ever before. However, the findings also highlight gaps in the scientific literature and the ongoing need for more data. Many assumptions were made due to no, missing, or limited data on crucial measures such as natural clearance rates and the percentage of asymptomatic infections. Population-based STI screening estimates are also greatly needed. Better data means more precise estimates and the ability to strengthen prevention and allocation efforts.