Georgia epidemiology report, Vol. 24, no. 4 (Apr. 2008)

April 2008

volume 24 number 04

Mosquito-Borne Viruses in Georgia, 2007

West Nile virus (WNv) is a mosquito-borne viral pathogen that was introduced into the United States (U.S.) in 1999. Within four years following its initial detection in New York, WNv was detected in East and West coast states as well as in Mexico and Canada. In Georgia, the virus was first identified in 2001. WNv is now considered endemic in most parts of the U.S., including Georgia.
West Nile virus is maintained in birds. It occasionally infects humans who are bitten by mosquitoes that have been feeding on birds. Most people (approximately 80%) infected with WNv do not develop symptoms. About one in five infected persons experiences a mild illness, (often termed "West Nile Fever" (WNF), characterized by fever, headache, muscle weakness or myalgia, arthralgia, and sometimes rash. Less than one percent of persons infected with WNv develop neurologic illness ("West Nile Neurologic Disease" or WNND) in the form of meningitis, encephalitis, or possibly acute flaccid paralysis. Approximately three to fifteen percent of WNND cases are fatal. Risk of WNND is associated with increasing age and the presence of underlying medical conditions.
Nationwide, 3,598 cases of WNv illness (both WNF and WNND) and 121 deaths were reported to the Centers for Disease Control and Prevention (CDC) during 2007 (as of March 4, 2008). In Georgia, any acute arboviral infection is a notifiable condition. However, the majority of cases of arboviral infection remain undetected if moderate or severe illness does not develop. During 2007, Georgia reported 52 confirmed cases of human WNv infection, including 1 death. Twenty five (48%) of the 52 cases experienced WNND (altered mental status, encephalitis, and/or meningitis) and 25 (48%) were diagnosed with WNF. The remaining two cases (4%) were asymptomatic. Three viremic blood donors were lost to follow up, symptoms were never recorded and therefore not included in the case count. A fourth blood donor went on to develop WNv symptoms and was counted as one of the 52 confirmed cases. The median age of cases was 55 years (range 4-91). The median age of those with WNND was 54 years (range 4-91). The age of the fatal case was 80 years. Thirty (58%) of 52 cases were male. As in past seasons, the majority of cases were reported during August and September (Figure 1). Fulton County reported the largest number (10) of WNv cases, followed by Muscogee County, which reported 7 cases. See Table 1 for the counties of residence of each WNv case.

# of Reported Cases

Figure 1. Arbovirus Cases in Georgia by Month on Onset-2007

Arbovirus Cases in Georgia by Month of Onset-2007
28

26

24

22

20

Chhikiuknugunngyaunya

18

LaaCCrorsossesEencEenphcaelitips halitis

16

DDeenngugeuFeeveFreve

14

EEaassteternrEnquEinqeuEinnceephEanlitics ephalitis

12

WWeesst tNiNle iVlierusVirus

10

8

6

4

2

0

January February
March April May June July
August September
October November December

Month of Onset

Table 1. Human WNv Cases by County of Residence, Georgia,

2007

County of Residence

Number of Cases

Fulton

9

Muscogee

7

Cobb

5

DeKalb

4

Bibb

3

Gwinnett

3

Habersham

3

Richmond

3

Crisp

1

Henry

2

Miller

2

Cherokee

1

Clarke

1

Clayton

1 (fatal case)

Columbia

1

Dougherty

1

Hall

1

Houston

1

Johnson

1

Mitchell

1

Tift

1

TOTAL County of Residence
Crisp Douglas Fulton

52 Positive Viremic Blood Donors
1 1 1

TOTAL

3

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Other Mosquito-Borne Viruses in Georgia

Human Testing for WNv and other Arboviruses

West Nile virus is one of several mosquito-borne viruses, also called arboviruses (arthropod-borne viruses) that circulate in Georgia. Other arboviruses identified in Georgia include Eastern Equine Encephalitis virus (EEE), LaCrosse virus (LAC) and rarely St. Louis Encephalitis virus (SLE), which is closely related to WNv. West Nile virus is the most commonly reported arbovirus in Georgia, although LAC infection is probably under-recognized because it typically causes only a mild clinical illness. EEE is the most severe of the arboviral infections, leading to death in 30-50% of symptomatic cases.
In addition to the 52 cases of WNv discussed previously, two confirmed cases and one suspect case of LAC encephalitis were reported in Georgia in 2007. One suspect case of EEE was also reported during 2007.

Commercial tests to detect WNv and other arbovirus antibodies are readily available at most commercial laboratories. During 2008, GDPH recommends that diagnostic testing for human arbovirus infections be performed at commercial laboratories. The Georgia Public Health Laboratory (GPHL) can perform testing for serologic evidence of infection with each of the arboviruses that circulate in Georgia, but due to limited lab resources, specimens will not be tested by GPHL unless they meet the criteria listed in Table 3. Please call the Georgia Division of Public Health (404-657-2588) or the appropriate District Health Office before submitting specimens for arboviral testing to assure that the criteria are met for testing at GPHL. If needed, specimens with positive results for WNv or other arboviruses at commercial laboratories can be confirmed at GPHL. Please do not submit specimens unless testing criteria are met; ineligible specimens will not be tested.

All acute arbovirus infections are reportable in Georgia, including those that are not acquired domestically. The Georgia Division of Public Health (GDPH) requires all acute arboviral infections to be reported because species of mosquitoes thrive in Georgia that are competent vectors for exotic diseases such as Dengue, Chikungunya and Yellow Fever. Although the risk of local transmission is low, it does exist. In 2007, 12 internationally acquired cases of arboviral infection were reported among Georgia residents, including 11 Dengue cases and 1 case of Chikungunya. Please see Table 2 for country of origin.

Table 2. Internationally-acquired arboviruses by country of origin, Georgia 2007

Internationally-Acquired Arbovirus
Dengue

Country of Origin Honduras

Dengue

Honduras

Dengue

Honduras

Dengue

Puerto Rico

Dengue

Nigeria

Dengue

Mexico

Dengue

Dominican Republic

Dengue

India

Dengue

Jamaica

Dengue

St Barts-Saint Barthelemy

Dengue

Nicaragua

Table 3. GPHL Arbovirus Testing Criteria for 2008
Adults To qualify for testing at GPHL, persons must be 18 years or older and meet at least one of the following clinical criteria: 1. Meningitis, OR 2. Encephalitis, OR 3. Acute onset of profound muscle weakness or acute flaccid
paralysis (including Guillian-Barre syndrome), OR 4. Fever (greater than 100.4F) and at least 2 of the
following : Headache Malaise Arthralgia Fatigue Eye Pain Children To qualify for testing at GPHL, persons must be 17 years or younger and meet at least one of the following criteria: 1. Fever (greater than 100.4F) with ataxia or extrapyramidal
signs, OR 2. New onset seizures or increased seizure activity in children
with pre-existing seizure disorders, OR 3. Encephalitis, OR 4. Acute onset of profound muscle weakness or acute flaccid
paralysis (including Guillian-Barre syndrome)
Note: Because meningitis due to other causes is rather frequent among children during arbovirus transmission season, children with meningitis will not be tested unless they meet additional criteria described above, or after other bacterial and viral etiologies have been ruled out.

Chikungunya

India

Division of Public Health http://health.state.ga.us
S. Elizabeth Ford, MD, MBA, FAAP Acting Director |State Health Officer

Martha N. Okafor, Ph.D. Deputy Director
John M. Horan, MD, MPH State Epidemiologist Epidemiology Section http://health.state.ga.us/epi

Georgia Epidemiology Report Editorial Board
Carol A. Hoban, M.S., M.P.H. Editor Kathryn E. Arnold, M.D.
Cherie Drenzek, D.V.M., M.S. John M. Horan, M.D., M.P.H. S. Elizabeth Ford, MD, MBA, FAAP Angela Alexander - Mailing List Jimmy Clanton, Jr. - Graphic Designer
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Georgia Department of Human Resources
Division of Public Health

Two Peachtree St., N.W. Atlanta, GA 30303-3186 Phone: (404) 657-2588
Fax: (404) 657-7517
Please send comments to: gaepinfo@dhr.state.ga.us

Arbovirus Surveillance in Sentinel Species

In addition to surveillance for human disease caused by arboviruses, GDPH and its partners also conduct surveillance for arboviruses in horses, birds and mosquitoes which help assess local risk of human disease. Below is a summary of arbovirus surveillance results in sentinel species during 2007.

Keeping gutters clear of debris Picking up trash in yards and neighborhoods Removing saucers from under outdoor potted plants Keeping window screens repaired Removing or covering all containers that may hold water

Bird Surveillance In areas where no mosquito surveillance occurs, bird surveillance has some use in predicting increased risk of human disease. However, the number of birds being submitted for testing in Georgia has been declining.
Horse Surveillance Like humans, horses are incidental hosts for WNv and other arboviral infections. Reports of confirmed infections in horses in an area indicate increased human risk because mammal-biting mosquitoes are transmitting virus. Public Health contacts the owners of arboviral-positive horses to educate them about their personal risk of disease and risk-reduction measures they can take on their farm to prevent future cases.
Due to increased immunity, increased vaccination, and decreased testing, there were no reported cases of WNv infection in horses reported in Georgia during 2007. In these circumstances, this surveillance system has limited usefulness in determining increased human disease risk. However, horse surveillance has been useful in rural Georgia counties where bird and mosquito surveillance resources are few.
Mosquito Surveillance Surveillance for WNv and other arboviruses in mosquito vectors is conducted to guide and evaluate mosquito control programs. Some level of mosquito surveillance was conducted in 28 of Georgia's 159 counties in 2007. In addition, the U.S. Army Center for Health Promotion and Preventive Medicine South (USACHPPM) conducted mosquito surveillance on military bases in Georgia, sharing those data with GDPH. Overall, intensive mosquito surveillance was conducted in fewer than 10 counties; WNv-positive mosquito pools were reported in seven of these counties. The first Georgia positive mosquitoes were detected in metro Atlanta in early July during 2007. The last positive pool was collected in Newton County in mid-October, with peaks in numbers of positive pools occurring in August.
Culex quinquefasciatus is the primary WNv vector in Georgia (Figure 2). It is a container-breeding mosquito that flies only a short distance from its breeding site when searching for a blood meal, and tends to remain close to water sources where it can lay its eggs after a blood meal.
Because Cx. quinquefasciatus tend to be a local problem, personal protection measures are important ways to reduce the risk of WNv infection. These include:
Wearing repellent Dumping out standing water at least once a week Keeping grass cut, leaves raked, and vegetation trimmed Applying larvicide to areas of standing water that cannot be
dumped out or drained

Figure 2: Culex quinquefasciatus Surveillance in Georgia, 20012007. The West Nile virus index, a quantitative measure used to
determine the local human risk threshold for epidemic transmis-
sion, is calculated by multiplying the minimum infection rate
for Cx. quinquefasciatus and the number of Cx. quinquefasciatus collected per trap night. Higher WNv Index numbers indicate
higher risk of human disease.

mosq / trap

65

0.20

Cx quinquefasciatus Surveillance

0.19

60

Georgia, 2001-2007

0.18

55

0.17

MEAN

0.16

50

WNv Index

0.15

45

0.14

0.13

40

0.12

WNv Index

35

0.11

0.10

30

0.09

25

0.08

0.07

20

0.06

0.05 15
0.04

10

0.03

0.02 5
0.01

0

0.00

52

51

50

49

48

47

46

45

44

43

42

41

40

39

38

37

36

35

34

33

32

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2 1

Jan

Feb Mar Apr May Jun

Jul

Aug Sep Oct Nov Dec

week / month

Summary

Based on data collected between 2001 and 2007, it is likely that WNv is now endemic throughout Georgia. However, lack of funding needed to collect mosquito population data and test vector species makes it difficult to predict human risk for any of the arboviruses currently found in Georgia or to help detect any newly introduced arboviruses. Continued monitoring of mosquitoes can help reduce the incidence of arboviral diseases in Georgia. Information obtained from these surveillance efforts should lead to responsible and informed decisions about mosquito control as well as public education about reducing mosquito breeding in yards and neighborhoods and prevention of mosquito bites.

For more information regarding arbovirus activity in Georgia, please visit http://health.state.ga.us/epi/vbd/mosquito.asp or call 404-657-2588.

Authors: Meghan M. Weems, M.P.H.; Rosmarie Kelly, Ph.D., M.P.H.; Marianne Vello, M.P.H.

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The Georgia Epidemiology Report Epidemiology Branch Two Peachtree St., NW Atlanta, GA 30303-3186

PRESORTED STANDARD U.S. POSTAGE
PAID ATLANTA, GA PERMIT NO. 4528

April 2008

Volume24Number04

Reported Cases of Selected Notifiable Diseases in Georgia, Profile* for January 2008

Selected Notifiable Diseases
Campylobacteriosis Chlamydia trachomatis Cryptosporidiosis E. coli O157:H7 Giardiasis Gonorrhea Haemophilus influenzae (invasive) Hepatitis A (acute) Hepatitis B (acute) Legionellosis Lyme Disease Meningococcal Disease (invasive) Mumps Pertussis Rubella Salmonellosis Shigellosis Syphilis - Primary Syphilis - Secondary Syphilis - Early Latent Syphilis - Other** Syphilis - Congenital Tuberculosis

Total Reported for January 2008
2008 38 121 14 0 46 42 23 5 9 2 0 1 0 0 0 83 105 1 6 11 41 0 39

Previous 3 Months Total Ending in January

2006

2007

2008

98

113

130

9072

10037

4879

46

52

51

1

3

6

161

131

157

4341

4534

1946

32

41

47

12

18

12

33

45

32

9

12

12

1

1

2

5

8

4

1

0

0

7

7

1

0

0

0

339

373

392

192

443

411

31

30

10

117

128

94

97

103

60

227

250

187

2

4

0

113

115

121

Previous 12 Months Total Ending in January

2006

2007

2008

592

588

688

34165

40474

38370

165

281

246

28

44

46

722

690

706

16249

20215

15686

107

123

136

115

65

62

178

205

145

38

39

43

7

7

11

14

22

22

2

4

0

46

31

12

0

0

0

1952

1866

2020

702

1419

1664

132

122

89

526

490

525

416

394

377

987

1029

1040

4

10

7

495

518

480

* The cumulative numbers in the above table reflect the date the disease was first diagnosed rather than the date the report was received at the state office, and therefore are subject to change over time due to late reporting. The 3 month delay in the disease profile for a given month is designed to minimize any changes that may occur. This method of summarizing data is expected to provide a better overall measure of disease trends and patterns in Georgia.
** Other syphilis includes latent (unknown duration), late latent, late with symptomatic manifestations, and neurosyphilis.
AIDS Profile Update

Report Period
Latest 12 Months**:
2/06-1/07
Five Years Ago:
2/02-1/03

Disease

Total Cases Reported*

Classification <13yrs

>=13yrs Total

HIV, non-AIDS

33

3,184

3,217

AIDS

8

1,671

1,679

HIV,

-

non-AIDS

AIDS

7

1,816

1,823

Percent Risk Group Distribution

Female MSM

IDU

MSM&IDU HS

Unknown

Perinatal

Race Distribution

White Black

Hispanic

26

21

2

1

4

72

<1

21

72

4

26

26

3

1

7

63

<1

19

73

5

-

-

-

-

-

-

-

-

-

-

27

36

7

2

16

38

<1

19

75

5

Other 2 3 1

Cumulative: HIV, non-AIDS 219

11,285

11,504

32

27

6

2

11

52

2

21

74

3

2

07/81-1/07 AIDS

240

32,222

32,462

20

44

15

5

14

22

<1

30

66

3

1

Yrs - Age at diagnosis in years

MSM - Men having sex with men

IDU - Injection drug users

HS - Heterosexual

* Case totals are accumulated by date of report to the Epidemiology Section ** Due to a change in the surveillance system, case counts may be artificially low during this time period

***HIV, non-AIDS was not collected until 12/31/2003

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