other animal species large and growing list of animals that have tested positive for wnv current...
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Other Animal Species
Large and growing list of animals that have tested positive for WNV
Current list at U.S. Geological Survey’s National Wildlife Health Center website at:
www.nwhc.usgs.gov
Dogs
Small Study (4 animals)
Low levels of viremia induced
None clinical
(Unpublished data to date-Michel Bunning, CDC-DVBID)
CatsSmall study
Viremia a little higher and longer than dogs
Parenteral: mild temp for 2-3 days
no CNS signs
Oral: fed infected mice
same level of viremia, no illness
Therefore-could be source for mosquitoes
WNV Positive Humans
Positive HumanWNV Cases 2002
577 cases51 deaths
0
5
10
15
20
25
7/20/2
002
7/27/2
002
8/3/20
02
8/10/2
002
8/17/2
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8/24/2
002
8/31/2
002
9/7/20
02
9/14/2
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9/21/2
002
9/28/2
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10/5/
2002
Onset Date
Nu
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ases
Confirmed Probable
Onset Date of Symptoms Among Human West Nile Virus Cases in Michigan as of November 5th, 2002
Age Groups of WNV Cases Michigan 2002
0102030405060708090
0-10 21-30
41-50
61-70
81-90
AGE IN YEARS
# Cases
Michigan Case Statistics:
All Cases
Age range: 9mo-95yrs
Ave Age: 57.6
% Female: 45
% Male: 55
Deaths
Age range: 24-95 yrs
Ave Age: 74.5
% Female: 41
% Male: 59
Types of Illness
80% asymptomatic
20% have flu-like symptoms
<1% have meningo-encephalitis/flaccid paralysis/other serious sequelae
~10% of those with serious CNS signs die
West Nile Meningo-encephalitis
Fever, headache
Altered mental status AND/OR
Stiff neck with CSF pleocytosis or elevated protein
Flaccid paralysis (poliomyelitis-type)
Diagnosis of Human Cases
CSF is best specimen
IgM Capture ELISA
PRNT (measure of IgG)
Serum-need paired sera to document a rise in titer
SLE cross reaction-must run concurrently
New Modes of Transmission
Transplant
Transfusion
Breast milk
Trans-placental
Occupational
Bird Surveillance Goals:
Collect information about dead bird sightings
Collect specimens for laboratory testing
Predict level of risk for human infection
Target intervention/prevention measures
Methods of Bird Surveillance
Citizen reports of dead or sick birds via hotline and website.
Laboratory testing of appropriate bird specimens.
Bias: Requires a person to find the bird and report it or submit it. Larger population areas will have more birds reported.
West Nile Virus Hot Line
Started in 2001
Toll Free #: 888-668-0869
Citizens call in to report dead bird
We requested reports of dead corvids
Request address and day bird was found, as well as willingness to collect bird for testing
Received 9,279 phone reports in 2002
WNV Hotline Calls* 2002
0
5000
10000
15000
20000
25000
July August September
# calls
888/668-0869
* >35,000 calls in Aug & Sept
Web-based Reporting
Accessed via www.michigan.gov/mda
Pilot program with Michigan State University
Received 1350 reports via the web
0
50
100
150
200
250
300
350
4/17/2
002
5/1/20
02
5/15/2
002
5/29/2
002
6/12/2
002
6/26/2
002
7/10/2
002
7/24/2
002
8/7/20
02
8/21/2
002
9/4/20
02
9/18/2
002
10/2/
2002
Date of Call
Nu
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alls
Phone Reports of Dead Birds in Michigan as of November 26th, 2002
Bird Surveillance Totals
Logged over 10,500 reports of dead birds and other animals
About 13% of reports came via the web
65% of dead birds reported were corvids (these were requested)
0
50
100
150
200
250
300
350
0
5
10
15
20
25
Phone Calls Human Cases
Phone Reports of Dead Birds versus Human Cases in Michigan as of November 26th, 2002
Potential Problems for Bird Surveillance in 2003
Bird immunity-crows could be less sensitive indicator of WN activity
Lack of web-based reporting for local and state reporting of diseases
Monitoring of bird reporting is labor intensive without technological support
Need to share data amongst agencies
Prevention
Source reduction
Personal protection
Mosquito control
Vaccine-horses only at this time
What Happened in 2002?
Expansion of endemic area to 44 states in the US
Huge epizootic/epidemic-especially in the Great Lakes and southern states
New modes of transmission discovered
Over 4000 human cases with more that 260 deaths
What to Expect in 2003?
Complete spread to the 48 states in the continental U.S.?
Bird immunity?
Human herd immunity?
Sporadic occurrence?
???????