West Nile Virus Update

1
West Nile VirusUpdate

• Nikki Sakata, MPH
• Office of Communicable Disease Control
• Central District Health Department

2
Objectives

• Outline history/origin of WNV
• Describe epidemiology of WNV
• Describe surveillance activities of WNV
• Describe the impact on Idaho
• Discuss future threat of WNV
• WNV research

3
Origin of WNV

• West Nile district in Uganda (Africa) 1937
• Severe human meningitis and encephalitis
• Predominant in elderly
• Recent outbreaks of WNV encephalitis have
  occurred in
• Algeria
• Czech Republic
• Democratic Republic of the Congo
• Russia
• United States
• Israel

4
History of WNV in the U.S.

• First identified on the east coast in 1999
• Spread further west every year since
• Disease identified in Idaho in 2004
• WNV exists in all 48 contiguous States
• Impact on wildlife more severe than in Africa,
  western Asia or Middle East

Source CDC - http//www.cdc.gov/ncidod/dvbid/west
nile/index.htm USGS - http//www.nwhc.usgs.gov/dis
ease_information/west_nile_virus/index.jsp
5
Mosquito 101

• In the United States
• 48 species of mosquitoes can carry or transmit
  WNV
• Only females transmit disease
• Culex pipiens (most common)
• Overwinter
• Live in urban areas (like dirty water)
• Transovarial transmission
• Minimum infection rate (MIR) over 10 (outbreak
  threshold)

Source USGS http//www.nwhc.usgs.gov/disease_info
rmation/west_nile_virus/index.jsp
6
Epidemiology

• Infectious agent
• Family Flaviviridae, genus Flavivirus
• Member of Japanese encephalitis virus antigenic
  complex (includes St. Louis encephalitis)
• Few genetic changes have occurred in WNV strains
  occurring in the U.S. since 1999

Source CDC - http//www.cdc.gov/ncidod/dvbid/west
nile/clinicians/epi.htmagent
7
Epidemiology
8
Epidemiology

• Hosts
• Birds
• 250 species of birds are hosts to WNV
• At least 18 mammal species
• Horses, humans, dogs, etc. have low
  infectious-level viremia dead end host
• Mode of Transmission
• Bite of an infected mosquito
• Alternative Modes of Transmission
• Transplanted organs
• Blood transfusions
• Breastmilk/Transplacental (mother-to-child)
• Occupational exposure

Source CDC - http//www.cdc.gov/ncidod/dvbid/west
nile/clinicians/epi.htmagent
9
Epidemiology

• Risk Factors
• Age
• Underlying health conditions
• Signs Symptoms
• Fever
• Headache
• Stiff neck
• Pleocytosis
• Incubation Period
• 3 14 days
• Confusion
• Coma
• Eye pain

Source CDC - http//www.cdc.gov/ncidod/dvbid/wes
tnile/clinicians/epi.htmagent Gorsche, R.
Tilley, P. (2005). The rash of West Nile virus
infection. Canadian Medical Association Journal,
172(11).
10
Epidemiology

• WNV related fatalities (Idaho, 2006)
• 23 deaths statewide in 5 out 7 health districts
• Average age 74.8 (range 46 92y)
• Gender Male (70.5)
• WNV manifestations
• 1st Encephalitis
• 2nd Neuroinvasive/Other
• 3rd Meningitis/Meningoencephalitis
• 4th - West Nile Fever

Source Idaho Department of Health and Welfare,
Office of Epidemiology and Food Protection.
(2006). Fall Epidemiology Conference Presentation.
11
Epidemiology

• Continued (Idaho 2006)
• Underlying conditions
• Coronary artery disease (CAD)
• CAD, A Fib
• Cardiomyopathy and chronic obstructive pulmonary
  disease (COPD)
• Terminal lung cancer
• Chronic lymphatic leukemia (CLL)
• Chronic myelogenous leukemia (CML), COPD, renal
  insufficiency
• Lupus

Source Idaho Department of Health and Welfare,
Office of Epidemiology and Food Protection.
(2006). Fall Epidemiology Conference Presentation.
12
Epidemiology
WNV Human Infection Iceberg
10 fatal (1 CNS case 150 total infections
20 West Nile Fever
Crude estimates
80 No symptoms
Source CDC
13
Clinical Spectrum
WN Meningitis
WN Fever
WN Encephalitis
WN Poliomyelitis GBS-Like Syndrome Radiculopathy
/ plexopathy
Source Idaho Department of Health and Welfare,
Office of Epidemiology and Food Protection.
(2006). Fall Epidemiology Conference Presentation.
14
Syndromes
Source Idaho Department of Health and Welfare,
Office of Epidemiology and Food Protection.
(2006). Fall Epidemiology Conference Presentation.
15
WN Fever Outcomes

• Long-term functional outcomes of 98 Illinois
  patients with WN Fever (2002 epidemic)
• Fatigue (96), headaches (71), concentration
  problems (53)
• 39 of WN Fever patients had symptoms that
  persisted for an average of 6 months

Source Watson, et al. (2004). Clinical
characteristics and functional outcomes of West
Nile fever. Annals Internal Medicine , 141(5).
16
WN Fever Outcomes

• Emerging Infectious Diseases Journal, July 2006
• Follow-up of persons following the 2003 Colorado
  epidemic
• 46 of patients stated that symptoms resolved in
  less than 30 days
• 6 month follow-up,12 reported muscle weakness,
  muscle pain, and/or headache

Source
17
WN Neuroinvasive Outcomes

• Elderly, immunocompromised higher rates of
  neuroinvasive disease, worse outcomes
• Pepperell, et al., Canada 2003
• 28 of 47 patients discharged home to independent
  living
• 79 with persistent neurological deficits at 30
  days
• Sejvar, et al., Louisiana 2002 (n16)
• Persistent difficulties in 14/15 at 8 months
• Persistence of tremor, Parkinsonism in 45

18
WN Neuroinvasive Outcomes

• Colorado
• Only 20 of meningitis patients, and 20 of
  encephalitis patients, reported recovery in
  days
• In a 2003 study (n25) detailed neurological
  exams and interview at 1, 4, and 12 months
• 18 of 27 re-evaluated at 1 year
• 6 deaths
• 3 lost to follow-up
• Ranges of outcomes
• 5 at or near baseline strength
• 6 significant improvement (1 increment
  improvement on MMT in affected limbs)
• 7 little or no improvement
• Less profound initial weakness ? better outcome

Manual muscle testing using Medical Research
Council 1-5 scale Source
19
WN Neuroinvasive Outcomes
Source OEFP, Division of Health (10/25/2006).
N131
20
WNV and Pregnancy

• CDC/Tulane Pregnancy Registry http//westnilepregn
  ancy.net/
• Voluntary participation
• Pregnancy tracked complications/adverse
  outcomes reported to CDC
• Placenta, umbilical cord, cord blood and breast
  milk tested
• Clinical status of mother and child tracked
• Infant development assessed at 24 months (Bayley
  Scales of Infant Development II test)
• Retinal exam by pediatric ophthalmologist

21
Testing

• Advantages
• Ruling out WNV
• Disadvantages
• Results do not dictate treatment
• Cost
• Recommendations
• Test more severe cases
• Idaho State lab will conduct confirmatory testing
  on the most severe cases

22
Treatment

• No specific treatment
• Severe cases supportive care
• Hospitalization
• Intravenous fluids
• Respiratory support
• Prevention of secondary infection

Source CDC http//www.cdc.gov/ncidod/dvbid/westn
ile/clinicians/epi.htmagent
23
Surveillance

• Combination of non-human and human surveillance
• Non-human early identification
• Positive mosquito pools
• Location of positive mosquito pools
• Identification of disease in other animals
  (birds, horses)
• Human
• Count cases
• Severity of illness
• Symptomatic vs. asymptomatic
• Location (difficult to know)

Source CDC http//www.cdc.gov/ncidod/dvbid/westn
ile/clinicians/epi.htmagent
24
Veterinary Surveillance

• Idaho 2006
• Llama
• Squirrels
• Bats
• Cow
• Ducks
• Condors
• Sage Grouse
• Idaho previous years
• Alligator
• Alpaca
• Dog

25
Prevention

• No human vaccine available
• Education
• Use mosquito repellants
• Permethrin on clothing
• DEET on skin
• Wear protective clothing
• Avoid outdoors from dusk to dawn
• Remove standing water around the home
• Place screens on windows and doors
• Integrated mosquito management

Source CDC http//www.cdc.gov/ncidod/dvbid/westn
ile/clinicians/epi.htmagent EPA
http//www.epa.gov/pesticides/health/mosquitoes/in
sectrp.htm
26
WNV in Idaho
Unfortunately, Idaho was 1 in the country for
WNV infections in 2006.
27
Affected Counties by Year
2005
2006
Evidence of WNV in birds, horses, or mosquitoes
Evidence of WNV in humans
Evidence of WNV in birds, horses, mosquitoes, or
humans
28
Aerial Spraying
1 case had onset dates prior to 6/15, 1 had
onset after 9/28. Cases with known onset dates
as of 10/25/2006. N 351. Source Office of
Communicable Disease Control, Central District
Health Department
29
Future Threat - Why the Increase?

• Establishment of WNV reservoirs and amplification
  hosts in local ecosystems
• Overwintering mosquitoes increasing virus in
  local ecosystem earlier in subsequent season
  (ramping up earlier)
• Climate?

30
Quiet Years?

• Background avian immunity elevated?
• Changes in avian population dynamics (are they
  all gone)?
• Weather/climate affecting vector mosquito
  populations?
• Fight the Bite worked?
• More vector control (abatement) districts?
• Significant decrease in reporting?
• Human immunity?

31
Research in Idaho

• Health Districts 3 4
• University of Pittsburgh and University of
  Oklahoma
• 2-part study
• Survey
• Blood draw
• Purpose
• Learn more about how the human immune system
  recognizes and attacks West Nile virus
• Develop better vaccines and better tests for West
  Nile virus.

32
Reporting

• Report cases within 3 days
• Suspect
• Confirmed
• Report to your District Health Department or the
  State WATTS line
• Why is it important?
• Track occurrence of disease
• Identify changes in virus strains
• Target prevention
• Integrated mosquito management

33
Conclusion/Resources

• Conclusions
• West Nile virus is here to stay
• Protection from mosquito bites is the only sure
  way to prevent WNV
• Resources
• Idaho Department of Health and Welfare
  http//www.healthandwelfare.idaho.gov/
• USGS http//www.nwhc.usgs.gov/disease_information/
  west_nile_virus/index.jsp
• CDC http//www.cdc.gov/ncidod/dvbid/westnile/index
  .htm
• http//www.westnilesurvivor.com/