Geographic Bridges for Importation of STD in

the Seattle Metropolitan Area:Barbarians at the Gates

Roxanne P. Kerani, Matthew R. Golden, William L.H. Whittington,

Hunter H. Handsfield, King K. Holmes

Background

• Bridges serve as links for subpopulations with differing prevalances of STD

• Geographic bridges may import STD from high to low prevalence regions

• Few studies have examined travel and STDs other than HIV

Objectives

• To describe geographic bridges residing

in the Seattle Metropolitan Area (SMA)

• To compare attributes of partnerships

involving partners residing in and

outside of the SMA

Methods• Data collected as part of a study of

expedited partner treatment

• Study period: Oct, 1998 – Jan, 2002

• Population: Residents of King Co., WA– Heterosexual– 14+ years– Diagnosed & reported with gonorrhea or

chlamydia– Contacted within 14 days of treatment

Methods• Exclusions:

– Current incarceration– No provider consent for contact– No sex partners (SP) in previous 60 days– Persons with unknown residence

• N = 3,123

• Interviews included questions regarding up to nine SPs in previous 60 days

Bridgers

King

Pierce

Snohomish

Participants with partners residing both in (local) and outside (distant) the SMA

Methods

• Analyses of individuals:

– Bivariate: T-tests and chi-squares

– Multivariate: Logistic regression

• Analyses of partnerships

– Bivariate: GEE models

Study Population

Bridgers

• 310 (9.5%) of participants reported at least

one distant partner

• 140 (4.9%) of participants reported both

local and distant partners (bridgers)

Percent BridgersDemographics & STD Dx

4.3%

6.3%

3.3%3.5%

5.4%

2.8%

4.2%5.3%

5.5%

3.7%

0%

2%

4%

6%

8%

10%

W 20+ Wh Oth CT Both

p=0.18p=0.06 p<0.01 p=0.02

M <20 GAA

Education, Employment, and Residence

5.7%6.2%

3.8%5.0%

3.5%4.3%

3.4%

0%

2%

4%

6%

8%

10%

HS <HS Full Part Un NE Oth

p<0.01p<0.01p=0.06

Number of Sex Partners

3.8

7.6

1.4

2.5

0

2

4

6

8

10

60 Days12Months

Non-Bridgers

Bridgers

*p<0.01

*

*

1.4

2.53.8

7.6

0

2

4

6

8

10

60 Days 12Months

Non-Bridgers

Bridgers

*p<0.01

*

*

Concurrency and Reason for Visit

8.3%

3.7%

6.1%

3.9%

0%

2%

4%

6%

8%

10%

Yes No Symptoms Other

<

p<0.01 p=0.01

Concurrency

Multivariate Results

1.79

1.031.61

2.21

1.53

1.80

1.40

1.0 1.5 2.0 2.5 3.0 3.5

Full time

Part time

North & East Side

Concurrency

White

Number SP

Gonorrhea

Odds Ratio

Results - Partnerships

• Partnerships among bridgers: N=329

• Residence of partners:

– 53% SMA

– 14% Elsewhere in WA

– 33% Within the US, outside WA

Partner Type and Ability to Contact

1.00

0.712.29

1.13

1.00

2.90

0.0 0.1 1.0 10.0

One time

Casual

Regular

Main

Can't Contact

Can Contact

Odds Ratio

Partner Knowledge of Infectionand Perceived Future Sex with SP

1.00

1.91

1.78

1.00

1.0 1.5 2.0 2.5 3.0 3.5

No

Yes

No

Yes

Partner Knows

Future Sex

Odds Ratio

Partnerships: Perceived Transmission Direction

1.00

1.53

0.63

1.00

0.0 0.1 1.0 10.0

Yes

No

Yes

No

Infectee

Transmitter

Odds Ratio

Summary

• 5% of patients were geographic bridges

• Bridgers were more likely to be white, older, employed, and of higher SES, and to report more partners and concurrency

• Distant partnerships were more likely to represent casual relationships with little potential for future contact

Limitations

• Study sample not representative of all

gonorrhea and chlamydia cases in King Co.

• Direction of transmission is unknown

• We don’t know where sex took place

• Anonymous partners may be underrepresented

Conclusions• Factors associated with bridging are

generally those associated with low rates of STD

• Bridges may be important in maintaining GC/CT endemicity in low prevalence populations

• Is business travel related to risky sex?

• Control of disease in some populations may require enhanced collaboration between distant public health agencies