Sexually Transmitted Disease Statistics

Division of Communicable Disease Epidemiology
Michigan Department of Health & Human Services

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The Sexually Transmitted Disease (STDs) statistics website reports statistics for three types of diseases: chlamydia, gonorrhea, and syphilis. Syphilis is grouped by all syphilis, or as primary and secondary syphilis (P&S Syphilis). P&S Syphilis reports represent initial stages of syphilis, when transmission is most likely to occur. Information for these diseases is presently available for the years 1997 through 2015. This information is divided into trend tables and yearly tables by gender, age, counties and health districts.

Overview: Chlamydia is the most commonly reported STD, at a rate of 480.7 per 100,000 population for 2015. During 2010-2014, chlamydia infections were reported on average at a rate of 483.7 per 100,000 population. Gonorrhea was the second most common infection, and was reported at a rate 107.0 in 2015. Primary and secondary infections due to syphilis occurred at 4.0 per 100,000 population. (See Number and Rate tables.)

Gender Disparity: Most STDs exhibit reporting disparities by gender. For example, in 2015, for every 2 males there were 5 females who were diagnosed with chlamydia. This ratio declined in older populations, until the ratio was about 1:1 for adults over the age of 45. In 2015, for every 5 males there were about 6 females who were diagnosed with gonorrhea; but for P & S syphilis, 10 males were reported, for every 1 female. (See Number of Cases, Rates and Percent Distribution tables.)

Trends: The accuracy of STD trends are influenced by two main factors: the proportion of infected people who are tested, and how completely those tests are reported to the health department. These factors have been relatively consistent for syphilis and gonorrhea reporting over the past dozen years, though with some modest improvement in completeness of reporting. However, reporting of chlamydia was first implemented in the 1990s and testing for this infection has increased dramatically. As noted in the Data Quality Considerations below, funding for testing has changed. Therefore, most of the increase in chlamydia reports prior to 2004 was due to improved testing and reporting.

Between 2004-2007, STD rates were stable, with no statistical trend observed. Chlamydia cases subsequently occurred at a rate (per 100,00) of 468.0 in 2008 and 487.4 2009, which is close to the 2015 rate of 480.7. Over the same period, reports of gonorrhea declined by about 43%, from 180.0 per 100,000 in 2008, to 107.0 in 2015. The incidence of syphilis is much less frequent than chlamydia and gonorrhea. In 2002, the rate of all syphilis peaked at 11.7 per 100,000 about the same as the rate in 2015, 11.0 per 100,000. (See Rate of Chlamydia, Gonorrhea and Syphilis Cases by Sex 2001-2014 )


STD Case Rates, 1998-2015
Fig1. - Case Rate Trends of Chlamydia, Gonorrhea & All Syphilis in Michigan, 1998-2015

 

Data Quality Considerations

The completeness of the data presented in these tables is affected by two factors that relate to data accuracy and comparability. It is essential that these factors be considered in using the information particularly when comparing frequencies over time or between geographic areas. These factors are:

The patient must request medical services: The information is obtained from health care facilities providing testing to individuals with sexually transmitted diseases. Therefore, it is complete only in so far as individuals have sought testing and records of such testing have been reported to the Michigan Department of Health and Human Services. It is likely that the number of cases reported under represents the incidence of sexually transmitted diseases in the population. For chlamydia and gonorrhea, this under representation may be substantial.

Inconsistent testing: It is important to note that there is no state requirement that individuals requesting services at family planning, WIC, MIC and other state sponsored outpatient clinics be tested for chlamydia. Although the state does provide testing support in some clinics, testing for chlamydia may be an additional expense for many service providers. Therefore, some clinics in many counties may not routinely test clients for chlamydia. In addition, local municipalities may apply funds for such testing at their own discretion. This may lead to increased numbers of chlamydia cases being reported as greater funds are released for testing. Counties and local health departments where greater funds are made available for testing may show greater rates of chlamydia cases simply because they have been able to test more individuals.


Historically, race or Hispanic ethnicity data is considered over 90% complete for syphilis cases. Though collection of race information has proven more difficult for gonorrhea and chlamydia cases, collection of the data has improved over the last few years. Currently, the race data is about 75% complete for these diseases. Race and ethnicity data are expected to improve further over the next few years. Incomplete race statistics are provided in the interest of timely reporting.

For additional information on sexually transmitted diseases, please visit: Sexually Transmitted Diseases at Michigan.gov.

Last Updated: 7/25/2016