Georgia epidemiology report, Vol. 16, no. 9 (Sept. 2000)

September 2000

volume 16 number 9

Division of Public Health http://health.state.ga.us
Kathleen E. Toomey, M.D., M.P.H. Director
State Health Officer
Epidemiology Branch http://health.state.ga.us/epi
Paul A. Blake, M.D., M.P.H. Director
State Epidemiologist
Mel Ralston Public Health Advisor
Georgia Epidemiology Report Editorial Board
Carol A. Hoban, M.S., M.P.H. - Editor Kathryn E. Arnold, M.D. Paul A. Blake, M.D., M.P.H.
Susan Lance-Parker, D.V.M., Ph.D. Kathleen E. Toomey, M.D., M.P.H.
Angela Alexander - Mailing List Jimmy Clanton, Jr. - Graphics
Georgia Department of Human Resources
Division of Public Health Epidemiology Branch Two Peachtree St., N.W. Atlanta, GA 30303-3186 Phone: (404) 657-2588 Fax: (404) 657-2608
Please send comments to: Gaepinfo@dhr.state.ga.us
The Georgia Epidemiology Report is a publication of the Epidemiology Branch,
Division of Public Health, Georgia Department of Human Resources

West Nile Virus and West Nile Encephalitis
West Nile virus (WNV) emerged in the Western Hemisphere during 1999 when it caused an outbreak of encephalitis among humans, horses, and wild birds in the New York City (NYC) area. The mosquito-borne flavivirus is blamed for 62 cases of human encephalitis (including 7 fatalities), 25 cases of equine encephalitis (including 9 fatalities), and the death of hundreds of wild birds, which were mostly crows, during the summer and fall of 1999.
This year, hundreds of birds that succumbed to WNV infection have been found throughout the northeastern region of the United States and WNV positive mosquito pools have been identified in NY, NJ, CT, and MA. As of August 28, 2000 the currently known geographic distribution of WNV has expanded south to Baltimore, MD (where an infected crow was found in 1999), north to Clinton County, NY (which borders Canada and VT), east to Boston, MA, and west to Buffalo, NY. Five human cases of West Nile encephalitis have been identified this year through August 28, 2000. All five individuals are over 60 years of age and live in close proximity to areas where positive birds and mosquito pools were identified earlier this season.
The emergence of WNV in the northeastern United States has demonstrated the ease with which infectious diseases may be introduced to and established within new geographic areas. The 1999 outbreak also demonstrated that cooperation between medical, veterinary, public health, laboratory, and wildlife biology professionals is crucial to quickly detect and effectively respond to emerging diseases.
Due to concern that the virus has spread via migrating birds and will establish itself in new geographic areas, federally funded surveillance is now being conducted in 21 states or jurisdictions along the Atlantic and Gulf Coasts. This issue of the Georgia Epidemiology Report (GER) provides clinical and epidemiologic information about West Nile virus and West Nile encephalitis, and details the surveillance activities that are being conducted in Georgia. Up-to-date information about WNV and surveillance for WNV in Georgia may be found on the public health website at http://health.state.ga.us.
Agent: WNV is a flavivirus. It belongs to the Japanese encephalitis complex, which includes West Nile virus, St. Louis encephalitis, Japanese encephalitis, Murray Valley, and Kunjiin.
Reservoir and Mode of Transmission: Wild birds are the primary reservoir hosts. The virus is transmitted from infected birds to other birds or mammals by mosquitoes. Culex ssp. are probably the principal mosquito vectors; however, WNV positive pools of Aedes japonicus and Aedes triseriatus have also been found this season near the epicenter of the 1999 outbreak. Aedes japonicus and Aedes triseriatus are both active during the day, so measures to prevent mosquito bites should be taken at all times while outdoors. Humans and animals other than birds are dead end hosts; they do not play a role in the natural transmission of the virus. Direct human-to-human or bird-to-human transmission is not known to occur.
Occurrence: Historically, WNV has caused human encephalitis sporadically and in outbreaks in parts of Africa, West Asia, Eastern Europe, and the Middle East. The virus was identified in the Western Hemisphere for the first time in 1999 when it caused an outbreak of human encephalitis in the New York City area. Seroprevalence rates in endemic areas overseas have ranged from 10% to 50%. The 1999 New York strain has been sequenced and found to be most similar to a strain first isolated from a goose in Israel in 1998.

the United States. The Georgia Department of Human Resources,

Incubation Period: Usually 6 days (range 5 to 15 days) after the bite of Division of Public Health received almost $200,000 to boost laboratory

an infected mosquito.

capacity and oversee surveillance for West Nile virus in humans, horses,

and wild birds.

Symptoms: In endemic areas overseas, asymptomatic infections and

milder illnesses are more common than central nervous system (CNS) Human Surveillance:

disease. The ratio of symptomatic to asymptomatic cases ranges from

Active surveillance for viral encephalitis in humans is being

1:140 to 1:300. Milder illnesses have usually been characterized by fever,

conducted in 49 counties in South Georgia and coastal Georgia

headache, myalgias, arthralgias, lymphadenopathy, and a maculopapular

(Valdosta, Albany, Savannah, Waycross, and Brunswick Health

or roseolar rash affecting the trunk and extremities. Pancreatitis,

Districts). Diagnostic support is being offered to physicians

hepatitis, and myocarditis have occasionally been reported. CNS

treating hospitalized patients with symptoms of encephalitis when

involvement is rare and predominantly affects older patients. A

a bacterial etiology and herpes simplex virus have been ruled out.

serosurvey conducted at the epicenter of the 1999 NYC outbreak revealed

Acute- and convalescent-phase sera and CSF may be submitted for

19 seropositive individuals (of 677 surveyed) who exhibited mild

a panel of tests (to be performed by the Florida Department of

symptoms or no symptoms. Seroprevalence in the surveyed area was

Public Health Laboratory Services) that includes screening for

estimated at 2.6%.

WNV and other arboviruses.

Enhanced passive surveillance for arboviral infections in humans is

Special Diagnostic Clues for West Nile Encephalitis: Arboviral

conducted throughout the state. Appropriate clinical samples may

encephalidites typically cannot be distinguished without specific labora-

be submitted to the Georgia Public Health Laboratory (GPHL) for

tory testing. However, viral encephalitis associated with severe, diffuse

an arbovirus panel that will include screening for WNV. Samples

muscle weakness (characterized by flaccid paralysis and/or an axonal neuropa-

are being sent to the Centers for Disease Control and Prevention

thy by EMG testing) was a unique characteristic of the West Nile encepha-

(CDC) laboratory at Fort Collins, Colorado for testing now;

litis cases that occurred during the 1999 outbreak. Neurologic illness

however, GPHL will have the capacity to perform an arbovirus

(including both encephalitis and meningitis) is more common among older

panel in the future. Health care providers are reminded that WN

adults infected with WNV; therefore testing for West Nile virus should

encephalitis cannot be clearly distinguished from other arboviral

also be considered for adult patients hospitalized with aseptic meningi-

encephalidites based on clinical information alone. EEE, SLE,

tis. This is in contrast to children with aseptic meningitis, who are more

and LaCrosse encephalitis should be considered for residents of

likely to have enteroviral infection, especially in the late summer and early

Georgia who present with an illness that is clinically compatible

fall. For this reason, West Nile viral testing is less likely to be positive

with an arboviral infection. Therefore, screening for WNV alone

among patients aged 16 and younger who present with aseptic meningi-

will not be performed; rather, a panel of tests that includes EEE

tis. Physicians might also consider WNV infection in the differential

and SLE will be performed on all submissions.

diagnosis of Guillain-Barr syndrome, especially when associated with

fever, altered mental status or pleocytosis. Serologic testing for patients Equine Surveillance:

who have milder symptoms (such as fever and headache only), are asymp-

Enhanced passive surveillance for equine encephalitis is being

tomatic, or have simply been bitten by mosquitoes is not necessary or

conducted statewide. Large animal veterinarians are encouraged to

recommended. The likelihood of WNV infection among these patients

seek diagnostic support from Tifton Veterinary Diagnostic

is extremely low, especially in the absence of an outbreak.

Laboratory or Athens Veterinary Diagnostic Laboratory for all

horses with clinical CNS disease manifestations. Testing will be

Differential Diagnoses: (1) EEE, SLE, and LaCrosse encephalitis are

provided free of charge for horses exhibiting clinical signs of

endemic to Georgia and should be considered for any illness that is

encephalitis and will include screening for WNV and other

clinically compatible with an arboviral infection. (2) Enteroviruses

arboviruses after rabies virus is ruled out as an etiology.

circulate widely during the late summer and early fall and should

especially be considered for patients aged 16 years and younger with

Avian Surveillance:

encephalitis or aseptic meningitis. A polymerase chain reaction (PCR)

Active surveillance for arboviruses in wild birds is being performed

test or viral culture of cerebrospinal fluid (CSF) may be used to diagnose

by the Southeastern Cooperative Wildlife Diseases Study

enteroviral infection. (3) Herpes simplex viruses may be considered in

(SCWDS) at the University of Georgia College of Veterinary

patients with encephalitis and clinical signs and symptoms such as

Medicine. Targeted and non-targeted collection of several species

bizarre behavior, speech disturbances, olfactory hallucinations, focal

of resident and migratory birds is being conducted in Coastal,

seizures, or EEG changes localized to the temporal lobes. A PCR test or

Coastal Plain and Piedmont regions of the state. Blood is

viral culture of CSF can be diagnostic. (4) Varicella should be considered

collected and tested for antibodies to arboviruses including WNV.

in patients with encephalitis and a vesicular rash.

As of August 28, 2000, 1357 birds have been collected throughout

Georgia. Nearly half have been tested by virus isolation techniques

Treatment: There is currently no known effective antiviral therapy or

with no evidence of arboviral infection.

vaccine for WNV. Milder illnesses do not require therapy. In more

severe cases, intensive supportive therapy is indicated.

Passive surveillance for dead or ill birds is being conducted

statewide. Birds with no obvious causes of death or signs of

trauma are being reported to county health departments. Dead

Surveillance for West Nile virus in

crows and bluejays that have been dead for less than 24 hours and

Georgia:

are in good condition, as well as individuals from bird die-offs are

Georgia is one of the 21 jurisdictions that received federal funding to monitor the spread and geographic distribution of West Nile virus in

submitted to SCWDS for necropsy and WNV testing. As of August 28, 2000, 33 dead birds have been submitted and of the 26 birds for which results are available, none have shown evidence of

-2 - arboviral infection.

Identification of WNV as the cause of the 1999 outbreak:

Unusual bird die-offs were observed in the NYC area during the summer of 1999, before recognition of any human cases of encephalitis. The avian morbidity and mortality, which primarily affected crows, was attributed to an unknown encephalitic infection. While veterinarians and wildlife biologists suspected that the avian epidemic was somehow related to the human outbreak of encephalitis, they were convinced that the birds were not dying of EEE or SLE because the zoos flock of emus (which are excellent sentinels for EEE) was healthy and SLE has never been known to be fatal to birds. Their suspicions were confirmed when WNV was isolated from affected humans and crows. Because crows are particularly susceptible to WNV, and the vast majority of infected crows die, they are considered an important early warning sign that infection could be present in a specific area. In fact, the discovery of WNV-positive dead crows in the NYC area this year preceded the identification of positive mosquito pools by 6 weeks, the first human case by 8 weeks, the first horse case by 12 weeks and the seroconversion of a sentinel chicken by 12 weeks. Dead bird surveillance will continue to be an important component of surveillance for WNV in Georgia during 2001.
If evidence of WNV or other arboviruses is found in Georgia, the public will be alerted and encouraged to eliminate mosquito breeding habitats from around their homes and to protect themselves and their families from mosquito exposure. Adult and/or larval mosquito control may be conducted at the discretion of local health authorities.
How to Avoid Exposure to Arboviruses
The best way to prevent infections with West Nile virus and other mosquito-borne diseases is to avoid getting mosquito bites. Other viruses that are transmitted by mosquitoes, including those that cause St. Louis Encephalitis (SLE) and Eastern Equine Encephalitis (EEE), already exist in Georgia and the following precautions should be taken to prevent mosquito bites: Minimize time spent outdoors when mosquitoes are most active. If you go outdoors while mosquitoes are active, cover up by wearing
shoes, socks, long-sleeved shirts, and long pants. Consider using a mosquito repellant that contains DEET (N, N-diethyl-methyl-metatoluamide) on exposed skin. Use products containing 10% or less DEET for children and no more than 30% for adults. Do NOT use products containing DEET on infants. Carefully read and follow directions on the container and wash treated skin when mosquito exposure has ended. Make sure your home, porch, and patio have tight-fitting screens that keep mosquitoes out.
All mosquitoes need standing water for the first stages of development. To eliminate stagnant water around your home where mosquitoes can lay eggs: Dispose of old tin cans, jars, tires, plant pots, and any other
container that can hold water. Store wheelbarrows, buckets, boats, etc. upside down so that water cannot accumulate in them. Inspect rain gutters and downspouts and remove any leaves and other debris. Empty stagnant bird baths, lily ponds, small wading pools, etc. at least once a week. Properly maintain and treat backyard swimming pools. Cover any pool not in use so rainwater and leaves do not accumulate in it. Be sure the cover does not hold pockets of water.

Additional Reading
1. Tsai TF, Popovici F, Cernescu C, Campbell GL, Nedelcu NI. West Nile encephalitis epidemic in southeastern Romania. Lancet. 1998;352:767-771.
2. Hubalek Z, Halouzka, J. West Nile fevera reemerging mosquito-borne viral disease in Europe. Emerg Infect Dis. 1999;5:643-650.
3. Han LL, Popovici F, Alexander JP Jr, et al. Risk factors for West Nile virus infection and meningoencephalitis, Romania, 1996. J Infect Dis. 1999;179:230-233.
4. Lanciotti RS, Roehrig JT, Deubel V, et al. Origin of the West Nile virus responsible for an outbreak of encephalitis in the northeastern United States. Science. 1999:286:2333-2337.
5. Jia XY, Briese T, Jordan I, et al. Genetic analysis of West Nile New York 1999 encephalitis virus. Lancet. 1999;354:1971-1974.
6. Cunha BA. West Nile encephalitis. Infect Dis Practice. 1999;23:85-90.
7. Cernescu C, Nedelcu NI, Tardei G, Ruta S, Tsai T. Continued transmission of West Nile virus to humans in southeastern Romania, 1997-1998. J Infect Dis. 2000;181:710-712. MMWR: 1999;48:845-49.
8. CDC. Update: surveillance for West Nile virus in overwintering mosquitoesNew York, 2000. MMWR. 2000;49:178-179.
9. CDC. Update: West Nile Virus isolated from mosquitoes New York, 2000. MMWR. 2000;49:211.
10. CDC. Outbreak of West Nile-like viral encephalitisNew York, 1999. MMWR. 1999;48:845-849.
11. CDC. Update: West Nile-like viral encephalitisNew York, 1999. MMWR. 1999;48:890-892.
12. CDC. Update: West Nile virus encephalitisNew York, 1999. MMWR. 1999:48:944-946, 955.
13. CDC. Guidelines for surveillance, prevention, and control of West Nile virus infectionUnited States. MMWR. 2000;49:2528.
14. CDC. West Nile Virus Activity New York and New Jersey, 2000. MMWR. 2000;49:640-642.
15. CDC. Update: West Nile Virus Activity Northeastern United States, January-August 7, 2000. MMWR. 2000;49:714717.
This article was written by Catherine Rebmann, M.P.H.

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

Bulk Rate U.S. Postage
Paid Atlanta, Ga Permit No. 4528

September 2000

Volume 16 Number 9

Reported Cases of Selected Notifiable Diseases in Georgia Profile* for June 2000

Selected Notifiable Diseases

Total Reported for June 2000 2000

Previous 3 Months Total

Ending in June

1998

1999 2000

Previous 12 Months Total

Ending in June

1998

1999

2000

Campylobacteriosis

80

Chlamydia genital infection

2382

Cryptosporidiosis

5

E. coli O157:H7

6

Giardiasis

101

Gonorrhea

1579

Haemophilus influenzae (invasive)

7

Hepatitis A (acute)

27

Hepatitis B (acute)

24

Legionellosis

2

Lyme Disease

0

Meningococcal Disease (invasive)

4

Mumps

0

Pertussis

2

Rubella

0

Salmonellosis

200

Shigellosis

17

Syphilis - Primary

11

Syphilis - Secondary

26

Syphilis - Early Latent

47

Syphilis - Other**

45

Syphilis - Congenital

1

Tuberculosis

45

205

219

191

5889

9686

7175

24

33

26

30

7

11

245

244

261

4845

6056

4314

13

27

24

209

131

78

50

48

62

3

0

4

2

0

0

19

23

13

1

1

0

15

10

8

0

0

0

312

423

379

383

58

62

29

22

30

68

54

69

207

174

132

239

158

130

5

1

4

158

186

181

849 17932
116 51 1075 17205 52 848 276 7 12 106 2 26 0 1377 1397 141 291 959 991 17 622

830 28850
194 60 1288 21188 87 753 170 5 1 80 2 37 0 2023 672 123 243 789 767 17 630

623 30043
146 50 1377 20361 80 339 263 11 0 65 5 61 0 1895 284 148 314 637 733 20 657

* 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.

Report Period
Latest 12 Months: 7/99 - 6/00 Five Years Ago: 7/94 - 6/95 Cumulative: 7/81 - 6/00

Total Cases Reported*

Percent Female

AIDS Profile Update
Risk Group Distribution (%) MSM IDU MSM&IDU HS Blood

Unknown

1296

26.6

30.1

12.5

3

14.9

1.5

38

2308

19

46

22.2

6.2

14.5

1.9

9.3

22011

16.3

49.3

18.7

5.7

13

1.9

11.4

MSM - Men having sex with men

IDU - Injection drug users

HS - Heterosexual

* Case totals are accumulated by date of report to the Epidemiology Section

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Race Distribution (%) White Black Other

19.8 77.2

3

34.5 63.5

2

36.4 61.5

2.1