Georgia epidemiology report, Vol. 23, no. 5 (May 2007)

May 2007

volume 23 number 05

Mosquito-Borne Viruses in Georgia, 2006

Human Arbovirus Surveillance West Nile virus (WNv) is a mosquito-borne viral pathogen that was introduced into the United States in 1999. Within four years following its initial detection in New York, WNv was detected in states from the East to the West coast 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 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, 4,219 cases of WNv illness (both WNF and WNND) and 161 deaths were reported to CDC in 2006 (as of March 06, 2007). In Georgia, an acute arboviral infection is a reportable condition; however, the majority of cases of arboviral infection remain undetected if moderate or severe illness does not develop.

Table 1. Human Arbovirus Cases, Georgia 2006

Arbovirus Month of County of Clinical

Onset

Residence Syndrome

Fatal

EEE

September Whitfield

Yes

LAC

December Lowndes Fever

No

DENGUE October

Henry

Fever

No

WNv July

Dougherty Altered Mental No Status/Flaccid Paralysis

WNv July

Dougherty

Yes

WNv August

Fulton

Mild Illness/No No fever

WNv August

Dougherty Fever

No

WNv August

Fulton Fever

No

WNv September Cobb

Fever

No

WNv September Muscogee Fever

No

WNv September Chatham Fever

No

WNv* September Fulton

Unknown

No

*Positive Viremic Blood Donor

In 2006, Georgia reported 8 confirmed cases of WNv infection, including 1 death. One positive viremic blood donor was also identified. Two (25%) of the 8 cases experienced WNND (GuillainBarre Syndrome, altered mental status, encephalitis, meningitis, meningoencephalitis, or flaccid paralysis) and 5 (63%) were diagnosed with WNF. One case experienced a mild illness that included joint pain and mild headache, but no fever. The viremic blood donor was lost to follow up and symptoms were never recorded. The mean age of cases was 57 years (range 36-82). The mean age of those with WNND was 64 years (range 52-76). The age of the fatal case was 76 years. Six (75%) of 8 cases were male. All cases were reported between July and September (Figure 1, Table 1). Dougherty County reported the largest number (3) of WNv cases, followed by Fulton County which reported 2 cases. See Table 1 for the counties of residence of each WNV case.

Figure 1. Human Arbovirus Cases by Month of Onset, Georgia 2006

Arbovirus Cases in Georgia by Month of Onset-2006

5

LaCrosse Encephalitis

Dengue Fever

Eastern Equine Encephalitis

4

West Nile Virus

3

# of Reported Cases

2

1

0

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

Month of Onset
Other Mosquito-Borne Viruses in Georgia West Nile virus is one of several mosquito-borne viruses, also called arboviruses (arthropod-borne viruses) that circulate in Georgia. Other identified arboviruses 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 usually causes only a mild clinical illness. EEE is the most severe of the arboviral infections, leading to death in 30-50% of symptomatic cases and often leaving survivors permanently disabled.
In addition to the 8 cases of WNv discussed previously, one confirmed case of LaCrosse Encephalitis and one probable case of Eastern Equine Encephalitis were reported in Georgia in 2006. See Table 1 for the counties of residence and clinical syndrome for these cases. See Figure 1 for month of illness onset for these cases.

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All acute arbovirus infections are reportable in Georgia, including those that are not acquired domestically. The Georgia Division of Public Health 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 2006 one case of internationally-acquired Dengue fever was reported (See Table 1, Figure 1). The case had traveled to Haiti.
Human Testing for WNv and other Arboviruses Commercial tests to detect WNv and other arbovirus antibodies are readily available at most commercial laboratories. During 2007, 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. GPHL does not charge for WNv and arbovirus panel tests, but specimens should only be submitted to GPHL when commercial testing is not possible. Criteria for testing at GPHL were instituted in 2001 to conserve limited laboratory resources and were intended primarily to detect neurologic manifestations of arboviral infections. Table 2 displays the criteria for testing in 2007. Specimens will not be tested by GPHL unless they meet these criteria. Please call the Georgia Division of Public Health (404-6572588) 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 positive for WNv or other arboviruses at commercial laboratories can be retested at GPHL to verify the results. Please do not submit specimens unless testing criteria are met; ineligible specimens will not be tested.
Arbovirus Surveillance in Sentinel Species In addition to surveillance for human disease caused by arboviruses in Georgia, GDPH and its partners conduct surveillance for arboviruses in horses, birds, and mosquitoes to determine local risk of human disease. Decreased funding may make arbovirus surveillance programs more difficult. Below is a summary of arbovirus surveillance results for sentinel species in 2006.
Horse Surveillance Like humans, horses are incidental hosts for WNv and other arboviral infections. Reports of positive horses in an area indicate increased human risk because mammal-biting mosquitoes are transmitting virus. Public Health contacts the owners of horses with arboviral infections to educate them about their personal risk of disease and risk-reduction measures they can take on their farm to prevent future infections.

Table 2. GPHL Arbovirus Testing Criteria for 2007
Adults: To qualify for testing at GPHL, persons must be 18 years or older and meet at least one of the following criteria:
Meningitis, OR Encephalitis, OR Acute onset of profound muscle weakness or
acute flaccid paralysis (including Guillian-Barre syndrome), OR Fever (greater than 100.4F) and at least 2 of the following:
o Headache o Malaise o Arthralgia o Fatigue o 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: Fever (greater than 100.4F) with ataxia or extrapyramidal signs, OR New onset seizures or increased seizure activity in children with pre-existing seizure disorders, OR Encephalitis, OR 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 causes have been ruled out.
Due to increased immunity, increased vaccination, and decreased interest in testing, the reported number of WNv infections in horses decreased between 2005 and 2006, from 1 case to no cases. Reduced reporting of suspect equine cases makes this surveillance system less useful as a sentinel for determining human disease risk. Horse surveillance has been especially useful in rural counties where bird and mosquito surveillance resources are few.
There were 4 cases of EEE infection in Georgia horses during 2006; 75% died or were euthanized. This represents a decrease in cases from the 20 cases of EEE reported in horses in 2005. Unfavorable weather conditions in early spring 2006 led to a decrease in the numbers of Culiseta melanura mosquitoes, the zoonotic vector for EEE, and subsequently reduced the overall risk of EEE transmission to horses and humans in Georgia.

Division of Public Health http://health.state.ga.us
Stuart T. Brown, M.D. Director
State Health Officer

Epidemiology Branch http://health.state.ga.us/epi
Susan Lance, D.V.M., Ph.D. Director
State Epidemiologist

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. Susan Lance, D.V.M., Ph.D.
Stuart T. Brown, M.D. Angela Alexander - Mailing List Jimmy Clanton, Jr. - Graphic Designer
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Two Peachtree St., N.W. Atlanta, GA 30303-3186 Phone: (404) 657-2588
Fax: (404) 657-7517

Georgia Department of Human Resources
Division of Public Health

Please send comments to: gaepinfo@dhr.state.ga.us

Bird Surveillance Although the number of birds being submitted for arbovirus testing has continued to decrease, bird mortality surveillance remains a useful tool to determine the geographic range and extent of WNv and other arbovirus activity in Georgia. In areas where no mosquito surveillance occurs, bird surveillance can be useful in predicting increased risk of human disease. In 2006, 282 birds were submitted from 38 of 159 Georgia counties; a total of 15 WNv-positive birds were found in 7 of those counties. Crows and jays appear to be losing their importance in WNv surveillance, possibly due to decreases in local populations after 5 years of continued WNv transmission. Thirty percent of American crows and 25% of Blue Jays submitted for testing were positive for WNv (Table 3). No birds tested positive for EEE in 2006.

Table 3: WNv Isolation in Dead Birds, Georgia 2006

Species

Count

% WNv+

American Crow

10

30%

Blue Jay

32

25%

Carolina Wren

3

33%

Common Grackle

21

5%

Northern Cardinal

16

6%

Intensive mosquito surveillance was conducted in fewer than 10 Georgia counties. Five counties reported WNv-positive mosquito pools. The first positive mosquitoes were detected in metro Atlanta in July. The last positive pool was collected in Fulton County in mid-October, with peaks in numbers of positive pools occurring in August.
Culex quinquefasciatus, the primary WNv vector in Georgia (Figure 4), is a container-breeding mosquito that flies only a short distance from its breeding site when searching for a blood meal. Personal protection measures are ways in which the public can help reduce the risk of WNv infections for themselves and in their community. 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 can not be
dumped out or drained, keeping gutters clear of debris, picking up trash in yards and neighborhoods, removing saucers from under outdoor potted plants, keeping window screens repaired, and removing or covering all containers that may hold water.

Dead bird surveillance indicates there is some level of WNv transmission occurring almost year-round in Georgia (Figure 3). Based on currently available data, it is likely that there is transmission occurring from April or May of one year until January or February of the next, depending on meteorologic conditions.

Figure 4: Culex quinquefasciatus Surveillance, 2001-2006. Detection of WNv in mosquitoes indicates an increased risk of human disease. The WNv Index is the number of infected mosquitoes per trap night.

Figure 3: Dead Bird Surveillance, Georgia 2001-2006. Detection of WNv in dead birds indicates a potential for increased risk of human disease.
Mosquito Surveillance Mosquito surveillance is conducted to detect the presence of arboviruses among potential vectors and to guide and evaluate mosquito control programs. Some level of mosquito surveillance was conducted in 27 of 159 Georgia counties in 2006. In addition, the U.S. Army Center for Health Promotion and Preventive Medicine South (USA-CHPPM) conducted mosquito surveillance on military bases in Georgia and shared those data with GDPH.

It is likely that WNv is now endemic throughout Georgia. Increased monitoring of mosquito populations and arboviral testing are our best courses of action for reducing 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.

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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

May 2007

Volume 23 Number 05

Reported Cases of Selected Notifiable Diseases in Georgia, Profile* for February 2007

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 February 2007
2007 33 2828 11 4 37 1031 8 1 10 3 0 2 0 0 0 93 71 1 2 1 11 0 33

Previous 3 Months Total

Ending in February

2005

2006 2007

90

112

95

7980

9689

9864

18

48

38

5

4

5

175

150

115

3780

4634

3979

42

38

35

40

11

14

90

32

33

5

3

9

0

1

0

7

3

9

0

1

0

10

7

5

0

0

0

234

248

326

103

171

296

32

27

9

124

117

38

79

90

38

233

254

98

1

3

0

121

105

100

Previous 12 Months Total

Ending in February

2005 2006

2007

573

619

567

34328

34816

39377

160

180

273

25

31

45

907

721

666

16075

16616

19231

126

110

115

264

109

59

435

166

199

44

37

42

10

7

7

16

14

22

2

2

4

33

48

26

0

0

0

1921

1963

1943

604

738

1438

118

130

100

482

540

381

366

410

302

919

988

819

5

5

6

527

501

506

* 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**: 4/06-3/07 Five Years Ago:*** 4/02-3/03

Disease Classification
HIV, non-AIDS AIDS HIV, non-AIDS AIDS

Total Cases Reported*

<13yrs >=13yrs

18

3,024

10

1,965

-

-

2

1,505

Total 3,042 1,975 1,507

Cumulative: HIV, non-AIDS 243

10,378

10,621

Percent Female
30 28 26 33

Risk Group Distribution (%)

MSM

IDU

MSM&IDU HS

32

7

3

15

33

8

2

12

-

-

-

-

37

9

3

17

30

8

3

12

Race Distribution (%)

Unknown Perinatal White Black

Hispanic

43

0

20

74

5

44

0

22

71

6

-

-

-

-

-

33

-

19

75

5

47

2

22

74

3

Other 1 1 1 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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