Sexually Transmitted Infections on a 30-Year Rise Worldwide

Lorraine L. Janeczko, MPH

April 29, 2022

The incidence of sexually transmitted infection (STI) as well as disability-adjusted life-years (DALYs) increased worldwide over 30 years, according to an observational trend study from China.

"Most countries had a decrease in age-standardized rates of incidence and DALY for STIs, whereas the absolute incident cases and DALYs increased from 1990 to 2019," the authors write in The Lancet Infectious Diseases. "Therefore, STIs still represent a global public health challenge, especially in sub-Saharan Africa and Latin America, where more attention and health prevention services are warranted.

"Our study also suggested an upward trend of age-standardized incidence rates among young populations, especially for syphilis, after 2010," they add.

STIs Are a Major Worldwide Public Health Challenge

To assess global STI burden and trends, co–lead study author Yang Zheng, MD, of Zhejiang University School of Medicine in Hangzhou, Zhejiang Province, and colleagues analyzed data from the Global Burden of Disease (GBD) study 2019.

They calculated incidence and DALYs of STIs in the general population at national, regional, and global levels over 30 years. They also calculated annual percentage changes in the age-standardized incidence rate and the age-standardized DALY rate of the five STIs included in the GBD study.

Of 204 countries in GBD 2019, 161 provided data on syphilis, 64 on gonorrhea, 94 on chlamydia, 56 on trichomonas, and 77 on genital herpes. The authors included 95% uncertainty intervals (UIs) and used Bayesian meta-regression to model the data.

  • Overall, they found that the global age-standardized incidence rate of STIs trended downward, with an estimated annual percentage change of –0.04 (95% UI, –0.08 to 0.00) from 1990 to 2019, reaching 9535.71 per 100,000 person-years (8169.73 to 11,054.76) in 2019.

  • The age-standardized DALY rate decreased with an estimated annual percentage change of –0.92 (–1.01 to –0.84) and reached 22.74 per 100,000 person-years (14.37 – 37.11) in 2019.

  • Sub-Saharan Africa, one of the hotspots, had the highest age-standardized incidence rate (19,973.12 per 100,000 person-years, 17,382.69 – 23,001.57) and age-standardized DALY rate (389.32 per 100,000 person-years, 154.27 – 769.74).

  • The highest incidence rate was among adolescents (18,377.82 per 100,000 person-years, 14,040.38 – 23,443.31), with stable total STI trends except for an increase in syphilis between 2010 (347.65 per 100,000 person-years, 203.58 – 590.69) and 2019 (423.16 per 100,000 person-years, 235.70 – 659.01).

  • The age-standardized incidence rate was higher among males (10,471.63 per 100,000 person-years, 8892.20 – 12,176.10) than females (8602.40 per 100,000 person-years, 7358.00 – 10,001.18), whereas the age-standardized DALY rate was higher among females (33.31 per 100,000 person-years, 21.05 – 55.25) than males (12.11 per 100,000 person-years, 7.63 – 18.93).

The Authors Deliver a Call to Action

"This paper is a call to action to focus on the STI pandemic with granular data on key target populations," Yukari C. Manabe, MD, FIDSA, FRCP, who was not involved in the study, told Medscape Medical News. "If behavioral messaging and testing in adolescents is not improved, HIV incidence rates will be impacted, and the gains that have been made in this area will be threatened.

Dr Yukari Manabe

"Although the number of countries from which data could be culled was limited, the change in incident cases is particularly striking, with most countries showing an increase and with African countries showing the largest rise," said Manabe, professor of medicine, international health, and molecular microbiology and immunology at Johns Hopkins Medicine and director of the Johns Hopkins Center for Innovative Diagnostics for Infectious Diseases, in Baltimore, Maryland.

"The increase in syphilis incidence rates, particularly in younger people, including men who have sex with men, is also alarming," she added in an email. "It is interesting to see the gender gap grow as more countries adopt antenatal syphilis screening."

Dr Ken Ho

Ken S. Ho, MD, MPH, infectious diseases specialist and medical director of the Pitt Men's Study at the University of Pittsburgh School of Medicine in Pennsylvania, called the study's findings a wake-up call for clinicians to discuss sexual health and wellness with their patients, to increase STI screening, and to address STI stigma.

"Overall, STI rates in most countries have trended down, but paradoxically, the number of cases may be going up, because we have more younger, sexually actively people," Ho said in an email.

"The study helps us understand the populations most impacted by STIs and allows us to design and create public health interventions that target the most impacted communities and demographic groups," Ho, who also was not involved in the study, added. "It allows us to reflect on how we address disparities. For example, the greater burden of disease seen in women may be due to the fact that women may not be screened and are diagnosed later."

Ho explained that the high STI rates in sub-Saharan Africa and Latin America are thought to be due to factors such as poverty and limited access to healthcare, known drivers of healthcare disparities.

The 2016 global incidence of common STIs was estimated to be up to 563.3 million, including 6.3 million cases of syphilis, 86.9 million cases of gonorrhea, 127.2 million cases of chlamydia, 156.0 million cases of trichomonas, and 186.9 million cases of genital herpes, the authors write.

The World Health Organization aims to end the STI epidemic by 2030, they note.

The study was funded by Mega-Project of National Science and Technology for the 13th Five-Year Plan of China and the National Natural Science Foundation of China. The authors, Manabe, and Ho have disclosed no relevant financial relationships.

Lancet Infect Dis. Published online December 20, 2021. Abstract

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