There were 12,120 children with S. aureus infections from 1,969 census tracts during 2002-2010 who were seen at Children’s Healthcare of Atlanta’s two pediatric hospitals. For Atlanta’s 20 counties’ MSA, there were 9,095 patients, < 19 years of age, from 901 census tracts. Overall, the number of infections increased steadily from 2002 to 2010, with the highest rates occurring in 2009 for CO-MRSA and 2008 for CO-MSSA; CO-MRSA rates increased at a higher rate compared to CO-MSSA. Of six possible combinations for trends of CO-MRSA and CO-MSSA infections, there were five group-based trajectory patterns for CO-MRSA (3) and CO-MSSA (2) with overlapping U.S. census tracts as shown in Table 2; no census tracts fell into the group-based trajectory pattern of Very High CO-MRSA - High CO-MSSA infections. Figure 2 shows the three CO-MRSA group-based trajectory trends and the two CO-MSSA group-based trajectory trends over this nine-year period: Of the three CO-MRSA group-based trajectory trends, only 0.8% of the census tracts showed a dramatic increase over the first six years followed by a gradual decline in the last three years; over two thirds (67.2%) remained in the low infection trend across all years. In contrast, for CO-MSSA, 85.7% of census tracts fell into the high infection group-based trajectory pattern which lasted throughout the nine-year period, compared to 14.3% of census tracts which belonged to a low infection trend over this same period. (Supplemental Section: Table A shows the coefficients for the terms used in the three group-based CO-MRSA trajectory models and the two group-based CO-MSSA trajectory models. For the three CO-MRSA group-based models, the equations all contained a quadratic term. For the two CO-MSSA group-based models, the equations contained a quadratic term, and a slope term that was relatively flat.)
Table 2. US Census Tracts with Community onset MRSA- / MSSA- Infection Group-Based Trajectory Patterns, 2002-2010
CO-MRSA Infection
Category
|
CO-MSSA Infection
Category
|
Low
|
High
|
Total
N
|
N (%)
|
N (%)
|
Low
|
682 (75.7%)
|
29 (3.1%)
|
711
|
High
|
170 (18.9%)
|
14 (1.6%)
|
184
|
Very High
|
6 (0.7%)
|
0
|
6
|
Total
|
858
|
43
|
901
|
From 901 census tracts with S. aureus infections, 682 (75.7%) were in the low infection group-based trajectory for both CO-MRSA and CO-MSSA (this is the ‘best’ trend category); deviant trajectory census tracts included 6 (0.7%) with Low CO-MSSA infection rate but Very High CO-MRSA infection rate, 170 (18.9%) Low CO-MSSA and High CO-MRSA infection rates and 29 (3.2%) High CO-MSSA and Low CO-MRSA infection rates. High CO- MSSA- High CO-MRSA (worst group-based trajectory) were seen in 14 (1.6%) census tracts. In 2002, there were 38 cases (0.03 infection per 1,000 children) in the Low CO-MRSA infection trajectory group, but this trend over time increased steadily to peak at 334 cases (0.48 infection per 1,000 children) in 2008, before declining to 257 cases (0.43 infection per 1,000 children) in 2010. Similarly, CO-MSSA low infection trajectory group had a baseline of 192 cases (0.18 infection per 1,000 children) in 2002, but this trend peaked later in 2009 with 560 cases (0.51 infection per 1,000 children) before dipping slightly to 482 cases (0.47 infection per 1,000 children) in 2010. Census tracts that started with High CO-MRSA infection trajectory followed a similar pattern of increasing with each year, beginning with 29 cases (0.15 infection per 1,000 children) in 2002, peaking to 454 cases (1.25 infection per 1,000 children) in 2008, before dropping to 422 cases (0.99 infection per 1,000 children) in 2010. Comparatively, High CO-MSSA infection trajectory more than tripled in infections over six years from 32 cases (0.46 infections per 1,000 children) to 102 cases (1.26 infections per 1,000 children). Like other trajectories, its rates also dropped after 2008 with 88 cases (1.02 infection per 1,000 children) in 2010. (Table 3)
Table 3. Counts of Community Onset MRSA and MSSA And Average Infection Rates by Group-Based Trajectory Patterns
Year
|
Type of Trajectory Pattern
|
CO-MSSA-Low
|
CO-MSSA-High
|
CO-MRSA-Low
|
CO-MRSA-High
|
CO-MRSA-Very High
|
Count (Rate)
|
Count (Rate)
|
Count (Rate)
|
Count (Rate)
|
Count (Rate)
|
2002
|
192
|
0.18
|
32
|
0.47
|
38
|
0.03
|
29
|
0.15
|
0
|
0.00
|
2003
|
362
|
0.36
|
58
|
0.79
|
74
|
0.10
|
69
|
0.34
|
1
|
0.14
|
2004
|
332
|
0.32
|
50
|
0.63
|
122
|
0.24
|
165
|
0.49
|
3
|
0.40
|
2005
|
382
|
0.35
|
61
|
0.76
|
219
|
0.30
|
274
|
0.80
|
6
|
0.71
|
2006
|
476
|
0.43
|
83
|
1.07
|
269
|
0.49
|
386
|
0.99
|
19
|
2.24
|
2007
|
419
|
0.38
|
89
|
1.14
|
312
|
0.47
|
416
|
1.16
|
24
|
2.91
|
2008
|
525
|
0.47
|
102
|
1.27
|
334
|
0.48
|
454
|
1.26
|
27
|
3.24
|
2009
|
560
|
0.51
|
87
|
1.09
|
312
|
0.48
|
445
|
1.15
|
25
|
2.54
|
2010
|
482
|
0.47
|
88
|
1.02
|
257
|
0.43
|
422
|
0.99
|
13
|
1.71
|
For each census tract with S. aureus occurence, we determined the number of CO-MSSA or CO- MRSA infections per 1,000 children <19 yearst. The actual number of CO-MSSA or CO-MRSA by year is provided along with the rate (infections per 1,000).
From aggregated individual level data of early and late time periods (2002-2005 and 2006-2010), we identified significant differences in both time periods, across the all three CO-MRSA infection group-based trajectories and also differences between the high and low CO-MSSA infection group-based trajectories (Table 4): Rates of blacks increased for CO-MRSA group-based trajectories as the CO-MRSA group-based trajectory moved from low to very high infection trend patterns, and overall, were relatively higher than rates of whites with MRSA infections. This finding remained consistent for both early and late time periods. Health insurance status also was significantly different across the three CO-MRSA infection trajectories with public health insurance ranking highest (p=0.0002) in CO-MRSA-High and CO-MRSA-Very High groups. Having prior hospitalization was significantly different among the three CO-MRSA infection trend patterns (p <0.05) in 2002-2005 but not significant in 2006-2010. Having a skin and soft tissue infection (SSTI), the most common clinical presentation for S. aureus in the community or outpatient setting, was not significant among the three CO-MRSA infection trend patterns in 2002-2005 or 2006-2010. In contrast, rates of whites increased for CO- MSSA group-based trajectories from low to high infection trend patterns, and overall, were relatively higher than rates of blacks with CO-MSSA infections. Rates among females were much higher in CO-MSSA High infection trend group, and the difference was statistically significant in the early period, 2002-2005 (p=0.0076). Rates of private health insurance was significantly higher than public health insurance in CO-MSSA low and high infection trajectory groups for both 2002-2005 (p=0.04140, and 2006-2010 (p=0.0057) periods. History of prior hospitalization was increased with CO-MSSA trajectory groups moving from low to high, in both 2002-2005 (p<0.001) and 2006-2010 (p<0.001). Rates of skin and soft tissues infections decreased in CO-MSSA trajectory groups moving from low to high, for both 2002-2005 (p=0.004) and 2006-2010 (p<0.001).
Table 4. Patient-level Characteristics of Group-Based Trajectory Patterns of MRSA and MSSA for 2002-2005/ 2006-2010
|
Patient Characteristic
|
MRSA-low
|
MRSA-High
|
MRSA-VeryHigh
|
|
MSSA-low
|
MSSA-high
|
|
(N= 2660)
|
(N=1937 )
|
(N= 118)
|
|
(N= 3730)
|
(N=650)
|
|
2002-2005, N= 537
|
2002-2005, N=453
|
2002-2005, N= 10
|
p-value
|
2002-2005, N= 1268
|
2002-2005, N= 201
|
p-value
|
2006-2010, N= 2123
|
2006-2010, N= 1484
|
2006-2010, N= 108
|
2006-2010, N= 2462
|
2006-2010, N= 449
|
Race**
|
|
|
|
|
|
|
|
2002-2005
|
|
|
|
<.0001*
|
|
|
0.0003*
|
Black
|
163(31.17%)
|
215(48.53%)
|
7(70%)
|
|
286 (22.95%)
|
25 (12.63%)
|
|
White
|
46(8.8%)
|
51(11.51%)
|
2(20%)
|
|
797 (63.96%)
|
155 (78.28%)
|
|
Other
|
314(60.04%)
|
177(39.95%)
|
1(10%)
|
|
163 (13.08%)
|
18 (9.09%)
|
|
2006-2010
|
|
|
|
<.0001*
|
|
|
<.0001*
|
Black
|
758(36.32%)
|
878(60.05%)
|
87(80.56%)
|
|
816 (34.1%)
|
94 (21.76%)
|
|
White
|
1113(53.33%)
|
455(31.12%)
|
14(12.96%)
|
|
1287 (53.78%)
|
286 (66.2%)
|
|
Other
|
216(10.35%)
|
129(8.82%)
|
7(6.48%)
|
|
290 (12.12%)
|
52 (12.04%)
|
|
Ethnicity (Hispanic)***
|
|
|
|
|
|
|
2002-2005
|
7(2.18%)
|
11(5.85%)
|
0(0)
|
0.078
|
n/a
|
n/a
|
n/a
|
2006-2010
|
175(13.09%)
|
118(17.05%)
|
7(19.44%)
|
0.0392
|
251 (16%)
|
51 (17.47%)
|
0.5321
|
Gender (Female)
|
|
|
|
|
|
|
2002-2005
|
262(48.79%)
|
245(54.08%)
|
3(30%)
|
0.0972
|
535 (42.19%)
|
105 (52.24%)
|
0.0076*
|
2006-2010
|
1073(50.54%)
|
782(52.7%)
|
68(62.96%)
|
0.0272*
|
1137 (46.18%)
|
220 (49%)
|
0.2714
|
Health Insurance
|
|
|
|
|
|
|
2002-2005
|
|
|
|
0.0002*
|
|
|
0.0414*
|
Private
|
269(50.09%)
|
179(39.51%)
|
0(0)
|
|
776 (61.2%)
|
140 (69.65%)
|
|
Public
|
250(46.55%)
|
258(56.95%)
|
10(100%)
|
|
456 (35.96%)
|
54 (26.87%)
|
|
Other****
|
18(3.35%)
|
16(3.53%)
|
0(0)
|
|
36 (2.84%)
|
7 (3.48%)
|
|
2006-2010
|
|
|
|
<.0001*
|
|
|
0.0057*
|
Private
|
935(44.04%)
|
464(31.27%)
|
17(15.74%)
|
|
1163 (47.24%)
|
246 (54.79%)
|
|
Public
|
1080(50.87%)
|
906(61.05%)
|
86(79.63%)
|
|
1163 (47.24%)
|
188 (41.87%)
|
|
Other****
|
108(5.09%)
|
114(7.68%)
|
5(4.63%)
|
|
136 (5.52%)
|
15 (3.34%)
|
|
SSTI Diagnosis
|
|
|
|
|
|
|
2002-2005
|
336 (62.57%)
|
252 (55.63%)
|
7 (70%)
|
0.0632
|
352 (27.76%)
|
32 (15.92%)
|
0.0004*
|
2006-2010
|
1495 (70.42%)
|
1077(72.57%)
|
79 (73.15%)
|
0.3389
|
1082 (43.95%)
|
141 (31.4%)
|
<.0001*
|
History of Hospitalizations
|
|
|
|
|
|
|
2002-2005
|
29 (5.4%)
|
55 (12.14%)
|
0
|
0.0005
|
210 (16.56%)
|
70 (34.83%)
|
<.0001
|
2006-2010
|
100 (4.71%)
|
63 (4.25%)
|
2 (1.85%)
|
0.373
|
214 (8.69%)
|
100 (22.27%)
|
<.0001*
|
*p-value <0.05, means statistically significant.
** Other races include: Asian, Native Hawaii, Alaskan, and Multiple-races (self identified by patients as more than one race).
***Other health insurance types include: Self-pay, no insurance, and those with both private and public.
Patient level data aggregated into two periods, 2002-2005 and 2006-2010, and then stratified by MRSA and MSSA population characteristics respectively based on MRSA and MSSA trajectory groups. (There are 9095 patients that accounted for the five different group-based trajectory patterns who resided within the 20 counties of Atlanta MSA across all years, <19 years.)
Comparing population data from US Census 2000 and 2010, we found significant differences among socio- economic and demographic variables, stratified by CO-MRSA- and CO-MSSA- group-based trajectory patterns (Table 5): Similar to what was seen with individual level data, we also found rates of whites decreased as the CO-MRSA group-based trajectories moved from low infection to very high infection in both US Census 2000 and 2010. In contrast, the rates of blacks increased as the CO-MRSA infection trajectories moved from low to very high for both U.S. Census 2000 and 2010. For CO-MSSA group-based trajectories, a similar pattern was also seen whereby, rates of whites increased as CO-MSSA moved from low to high both in U.S. Census 2000 (p=0.054) and U.S. Census 2010 (p=0.0096). In CO-MSSA group-based trajectories, proportions of blacks decreased as infection trends increased; these trends were significant for both U.S. Census 2000 (p=0.0158) and 2010 areas (p=0.001). Although the proportion of census tracts with children <19 years of age increased as infection trends increased for both CO-MRSA and CO-MSSA group-based trajectories, and relatively higher in U.S. Census 2010 compared to 2000, none of the CO-MRSA or CO-MSSA infection trend patterns were significant except for U.S. Census 2010 census tracts representing the CO-MSSA-High infection trend pattern.
Table 5. Population Area-level Characteristics of Group-Based Trajectory Patterns of MRSA and MSSA in Atlanta
Population
Characteristic
|
MRSA–Low
|
MRSA-High
|
MRSA-Very High
|
p-value
|
MSSA-Low
|
MSSA-High
|
p-value
|
|
N (%)
|
N (%)
|
N (%)
|
N (%)
|
N (%)
|
Census tracts
N=901 (%)
|
711 (67.2%)
|
184 (32%)
|
6 (0.8%)
|
|
858 (85.7%)
|
43 (14.3%)
|
|
Race/Ethnicity, %
|
|
|
|
|
|
|
|
White, %
|
|
|
|
|
|
|
|
2000
|
68.4
|
46.5
|
31.4
|
<.0001*
|
63.4
|
69.5
|
0.054
|
2010
|
59.4
|
39.8
|
21.5
|
<.0001*
|
54.6
|
65.3
|
0.0096*
|
Difference in Periods, %
|
-8.7
|
-6.2
|
-9.1
|
0.1188
|
-8.4
|
-4.2
|
0.0349*
|
Black, %
|
|
|
|
|
|
|
|
2000
|
24.3
|
44.9
|
63.3
|
<.0001*
|
29.1
|
21.8
|
0.0158*
|
2010
|
29.2
|
49.9
|
71.9
|
<.0001*
|
34.2
|
22.3
|
0.001*
|
Difference in Periods, %
|
4.8
|
4.1
|
8.2
|
0.981
|
4.9
|
0.8
|
0.0293*
|
Hispanic, %
|
|
|
|
|
|
|
|
2000
|
5.77
|
7.48
|
4.44
|
0.2315
|
6.02
|
8.04
|
0.6623
|
2010
|
9.8
|
10.8
|
5.7
|
0.3007
|
9.8
|
13.4
|
0.6361
|
Difference in Periods, %
|
3.8
|
3.6
|
1.7
|
0.8551
|
3.6
|
5.6
|
0.4351
|
<18 years, %
|
|
|
|
|
|
|
|
2000
|
26.4
|
27.1
|
29.5
|
0.4065
|
26.5
|
27.9
|
0.2359
|
2010
|
28.6
|
29.2
|
29.8
|
0.7528
|
28.6
|
30.8
|
0.0253
|
Difference in Periods, %
|
2.4
|
2.3
|
-0.9
|
0.3644
|
2.3
|
2.9
|
0.4148
|
K-12th Grades, %
|
|
|
|
|
|
|
|
2000
|
71.3
|
72.6
|
76.1
|
0.2774
|
71.4
|
73.9
|
0.6034
|
2010
|
67.9
|
69.0
|
69.6
|
0.8499
|
67.9
|
73.9
|
0.0042*
|
Difference in Periods, %
|
-2.9
|
-3.0
|
-6.8
|
0.6411
|
-3.1
|
-0.2
|
0.0415
|
Nursery to preschool, %
|
|
|
|
|
|
|
2000
|
8.9
|
8.5
|
7.2
|
0.177
|
8.8
|
9.3
|
0.2455
|
2010
|
7.9
|
7.6
|
5.6
|
0.401
|
7.7
|
8.6
|
0.115
|
Difference in Periods, %
|
-1.0
|
-1.0
|
-2.0
|
0.9299
|
-1.0
|
-0.6
|
0.2138
|
High School, %
|
|
|
|
|
|
|
|
2000
|
24.6
|
25.8
|
26
|
0.3111
|
25.0
|
21.4
|
0.0295*
|
2010
|
24.7
|
28.3
|
29.7
|
0.0002*
|
25.7
|
22.1
|
0.0431*
|
Difference in Periods %
|
0.2
|
2.4
|
3.8
|
0.0002*
|
0.7
|
1.0
|
0.5
|
Bachelor, %
|
|
|
|
|
|
|
|
2000
|
21.7
|
18.5
|
14.5
|
0.0085*
|
20.8
|
25.6
|
0.0255*
|
2010
|
23.7
|
19.1
|
16.2
|
<.0001*
|
22.5
|
26.9
|
0.0327*
|
Difference in Periods, %
|
1.91
|
0.45
|
1.7
|
0.0022*
|
1.6
|
1.0
|
0.8262
|
Graduate or professional, %
|
|
|
|
|
|
|
2000
|
10.4
|
9.0
|
8.8
|
0.0839
|
9.9
|
12.6
|
0.0801
|
2010
|
12.4
|
10.3
|
9.8
|
0.01*
|
11.8
|
14.1
|
0.208
|
Difference in Periods, %
|
2.0
|
1.4
|
-0.7
|
0.1914
|
1.9
|
1.0
|
0.2307
|
Labor Force, %
|
|
|
|
|
|
|
|
2000
|
70.6
|
69.35
|
69.35
|
0.2486
|
70.3
|
70.9
|
0.7147
|
2010
|
70.0
|
70.65
|
70.68
|
0.6528
|
70.2
|
70.2
|
0.7211
|
Difference in Periods, %
|
-0.6
|
1.2
|
0.3
|
0.0464*
|
-0.2
|
-0.7
|
0.7159
|
Median Annual Household Income^, $
|
|
|
|
|
|
2000
|
71,537.44
|
64,354.33
|
60,191.23
|
0.0048*
|
69,118.34
|
87,486.73
|
0.0043*
|
2010
|
63,983.19
|
54,450.01
|
45,369.67
|
<.0001*
|
61,026.01
|
79,598.74
|
0.0090*
|
Difference in Periods, $
|
-7,554.25
|
-9,904.32
|
-14,821.6
|
0.1179
|
-8,092.33
|
-7,887.98
|
0.4704
|
Median House Value^, $
|
|
|
|
|
|
|
2000
|
193,740.38
|
170,922.67
|
145,859.5
|
0.023*
|
186,692.81
|
230,044.26
|
0.0178*
|
2010
|
217,349.72
|
197,003.26
|
155,783.33
|
0.0365*
|
210,287.79
|
262,673.81
|
0.0158*
|
Difference in Periods, $
|
25,719.34
|
26,080.59
|
9,923.83
|
0.8035
|
24,761.96
|
44,466.64
|
0.0262*
|
Household Crowding**, %
|
|
|
|
|
|
|
2000
|
1.3
|
1.1
|
1.0
|
<.0001*
|
1.2
|
0.8
|
0.1311
|
2010
|
3.9
|
5.6
|
7.3
|
0.9937
|
4.3
|
4.1
|
0.0823
|
Difference in Periods, %
|
-2.7
|
-4.5
|
-6.1
|
<.0001*
|
-3.1
|
-3.3
|
0.6453
|
Poverty*** %
|
|
|
|
|
|
|
|
2000
|
9.1
|
10.7
|
10.1
|
<.0001*
|
9.5
|
7.40
|
0.0727
|
2010
|
18.3
|
19
|
17.0
|
0.0236*
|
18.6
|
14.1
|
0.0202*
|
Difference in Periods, %
|
8.8
|
7.6
|
6.1
|
0.7673
|
8.6
|
6.8
|
0.5399
|
Gini Index-2010
|
0.40
|
0.4
|
0.40
|
0.1912
|
0.4
|
0.4
|
0.858
|
A total of 901 census tracts from 20 counties in Atlanta (2000 and 2010) represent the patients with S. aureus infections who were included in the study.
*p-value <0.05, means statistically significant.
**Occupied households with >1 person/room.
***People living under poverty level in past 12 months.
^Median Annual Household Income and Median House Value for 2000 were adjusted to 2010, using an inflation calcuator.
Socio-economic conditions of the neighborhoods where CO-MRSA infection trends were higher differed from CO-MSSA infection trends over the same time period. For example, median household income and housing values decreased as CO-MRSA infection group-based trajectories moved from low to very high infection trends. Proportion of the population living below the federal poverty level also increased significantly in areas where CO-MRSA infection trends moved from low to very high infection rates. This trend was not seen with CO-MSSA group-based trajectories, where the median household income and housing values increased, and the proportion of the population living below the federal poverty level decreased in areas where it was clearly a CO-MSSA high infection trend pattern.
Since crowding is a known risk associated with community-associated MRSA infections, we calculated the percentage of U.S. 2000 census tracts with evidence of household crowding and found crowding increased significantly as trends of CO-MRSA infection moved from low infection to very high infection pattern (p<0.0001). However, rates of crowding in U.S. 2010 census tracts were not significantly different in those areas where CO-MRSA infection trends moved from low to very high (p=0.9937). In contrast, for CO-MSSA group-based trajectories, household crowding was not significantly increased over the different categories of CO-MSSA infection trends, nor was the change in rates between the two time periods significantly different (p=0.6453).
Spatial analyses of census tract group-based trajectories for MRSA and MSSA. Spatial variations of the different community onset MRSA-MSSA infection group-based trajectories were identified (Figure 3): The most favorable group-based trajectory (CO-MRSA Low infection and CO-MSSA Low infection) and second most favorable trajectory (CO-MRSA High-CO-MSSA Low) were scattered with higher proportion of census tracts in counties where the population is less dense relative to inner city Atlanta. There were also ‘pockets’ within Gwinnett, Henry and Douglas counties, where there were census tracts with CO-MRSA-Very High or CO-MRSA-High, even though most of the county fell into a more ‘favorable’ or lower infection group-based trajectory pattern. In contrast, counties representing the inner city (areas within DeKalb County and Fulton County) had the highest proportion of the worst trajectories (CO-MRSA-Very High-CO-MSSA-High or CO-MRSA-High-CO-MSSA-High). Seven of these census tracts, representing CO-MRSA Very High-CO-MSSA Low or worst group-based trajectory combination, were from areas located east of downtown Atlanta (DeKalb County) and a single census tract southeast of downtown Atlanta (Henry County). To identify areas where infections intensified with each year in a particular census tract and also in neighboring census tracts (‘hot spots’) compared to areas where the infections were much lower than neighboring census tracts across each year (‘cold spots’), we found CO-MRSA and CO-MSSA ‘hot’ and ‘cold’ spots overlapped in a number of areas over the 2002-2010 period. ‘Hot spots’ for CO-MRSA and CO-MSSA overlapped for a large number of census tracts located primarily in the most heavily populated counties (Dekalb, Fulton and Gwinnett), but CO-MRSA ‘hot spots’ extended much further down into the southern counties of Rockdale, Henry and Clayton compared to CO-MSSA ‘hot spots’. ‘Cold spots’ followed the perimeter of the ‘hot spots’ for both CO-MRSA and CO-MSSA. Interestingly, ‘cold spots’ were seen southeast of Fulton county, where there were CO-MRSA ‘hot spots’. There was a large band of cold spots, located in the northwestern portion of 20 counties boundaries, which ran along the perimeter of hot spots seen in Cobb and Cherokee counties (northwest of the most densely populated counties) (Figure 4). In order to discern what group-based trajectory patterns might fall within ‘hot spots’, we overlaid the group-based trajectory map with hot spots and found that the ‘worst’ group-based trajectory was located in areas found to be ‘hot spots’ for CO-MRSA and CO-MSSA, and the best trajectory groups tended to occur where there were neither cold nor hot spots. Interestingly, Bartow county (northwest of Atlanta’s downtown area) had a number of census tracts which had a CO-MRSA-high – CO-MSSA- low designation, yet no CO-MSSA or CO-MRSA ‘hot’ or ‘cold’ spots.