STD (Sexually Transmitted Diseases) Report
2009 Summary

St. Charles County Department of Community Health and the Environment
Alison Tucker, MSc
STD cases include Chlamydia, Gonorrhea, and Syphilis

There was a total of 814 laboratory confirmed reportable STD cases in 2009 among St. Charles County residents (Chlamydia, Gonorrhea and Syphilis cases). This is a 21.0% increase from the previous 5 year mean. Previous year’s total cases were 773, 602, 605, 664 and 571 for the years 2008, 2007, 2006, 2005 and 2004, respectively. As you can see from the graph below, the biggest increase is among Chlamydia cases.

FIGURE 1:

The population in St. Charles County has increased over the last few years so to show the prevalence of STD trends we need to look at the rates by population year. The graph below displays the STD rates per 100,000 people in St. Charles County using yearly population increases from the Economic Development Center of St. Charles County (http://www.edcstcharlescounty.com/facts/index.php3). From this graph we see that Gonorrhea rates have been decreasing, but that Chlamydia rates are still increasing. We had a drop in overall Syphilis rates in 2009 compared to 2008 (2.55 cases per 100,000 people compared to 4.29 in 2008), but these rates are still 2-3 times higher than what we were seeing from 2004-2007.

FIGURE 2:

Chlamydia
In 2009 there were 725 cases of Chlamydia reported to the Health Department, a 26.6% increase from previous 5 year mean. This is the highest number of Chlamydia cases we have seen in 5 years (figure 1). When looking at rates of Chlamydia there was a decrease in 2006 and 2007 with about 139 cases per 100,000 people and the past 2 years this has jumped to upwards of 200 cases per 100,000 people (figure 2). This increase is likely a combination of increase in morbidity, but also an increase in screening.

Compared to national rates, rates of Chlamydia in St. Charles County is about 1/2 of the national rate. National rates in 2008 were 401.3 cases per 100,000.

The female-male ratio the past 3 years have been 3.0 for Chlamydia cases, this corresponds to the national ratio. Prior to 2007 the female-male ratio was 4.5, the increase availability of urine screening for males may account for this (Figure 3).

The age groups 15-19 and 20-24 make up more than 75% of the Chlamydia cases in St. Charles County (Figure 4).   

FIGURE 3:

FIGURE 4:

Gonorrhea
In 2009 there were 80 cases of Gonorrhea reported to the Health Department, a 30.8% decrease from previous 5 year mean. This is the lowest number and rate of Gonorrhea cases we have seen in 5 years (figure 1, figure 2). 

Compared to national rates, Gonorrhea rates in St. Charles County are 1/5 of the national rate (national rate in 2008 = 111.6 cases per 100, 000).

When looking at the female-male ratio from 2004-2006 the average ratio was 2.7, but since 2007 this discrepancy has almost disappeared with the female-male ratio being 1.1, 1.1 and 1.0 the past 3 years respectively (figure 5).

The median age for Gonorrhea cases in 2009 was 22 years and like Chlamydia, most cases are in the 15-19 and 20-24 age groups with these 2 age groups making up 64% of reported cases (Figure 6).

FIGURE 5:

FIGURE 6:

Syphilis
 In 2009 there were 9 cases of Syphilis reported, a 28.9%  increase from the previous 5 year mean, but a decrease from the 15 cases reported in 2008.  There was a decline in the primary and secondary (P&S) stage cases and an increase in early latent cases (Figure 7). They have been no reports of congenital syphilis in St. Charles County in 2009.

Compared to national rates, P&S Syphilis rates in St. Charles County are about 1/3 of the national rate (national rate in 2008 = 4.5 cases per 100, 000).

Unlike Chlamydia and Gonorrhea where females outnumber males in case reporting, males outnumber females when it comes to total Syphilis cases on average 5 to 1 (figure 8). Age of diagnosis tends to be higher overall for Syphilis cases with most cases over 25 years of age, but when broken down by stage we can see that late latent stage syphilis cases are all older than 30 years of age (figure 9).

FIGURE 7:

FIGURE 8:

FIGURE 9:

Zip codes and STD Rates
The following table shows the 2009 rates and the previous 4 year mean rates of STD cases per zip code per 10,000 people. This was done using the 2000 population estimates for each zip code.  Please keep in mind that the rates most likely are inflated due to the current 2009 population estimate for each zip code.

We can see from this table that the highest number of cases in 2009 and the previous 4 year mean is in the 63301 (St. Charles City) zip code, a zip code with one of the highest numbers of college students. The highest rate of STD’s in 2009 was in the 63385 (Wentzville) zip code.