close

Вход

Забыли?

вход по аккаунту

?

West Nile Virus - UC Berkeley Graduate School of Journalism

код для вставкиСкачать
The Movement of West Nile Virus in North America
UC Berkeley
October 1, 2003
Photo of Cx. quinquefasciatus
courtesy of Dr. Stephen Higgs,
UTMB/Galveston
Lyle R. Petersen, M.D., M.P.H..
Division of Vector-Borne Infectious Diseases
Fort Collins, Colorado
Order of Topics
•
•
•
•
•
•
•
What is it?
What is different now?
How did it get here?
How it is spreading?
How big is the problem?
What will happen next?
How do we prevent it?
West Nile Virus: Background
• RNA virus
• Family Flaviviridae, Genus
Flavivirus
• Member Japanese encephalitis
serocomplex
• Closely related to SLE virus
• Isolation in 1937, West Nile district
of Uganda
West Nile Virus:
Approximate Geographic Range Before
1999
West Nile Virus Before and After Mid-1990s
• Before
• Mild self-limited febrile illness
• Central nervous system involvement rare
• Periodic outbreaks
• After
• Outbreaks associated with severe CNS illness
• Some outbreaks associated with avian mortality
• First recognition in North America (New York City)
in 1999
West Nile Outbreaks
• Israel 1941, 1951-1954, 1957, 1980,
2000
• France 1962, 2000
• South Africa 1974
• Romania 1996
• Italy 1998
• Russia 1999
• United States 1999-2003
Arrival in
North
America
Phylogenetic Tree
of West Nile
Viruses
Clade
Egypt 1951
France 1962
South Africa 1974
LINEAGE
Eg 101
NE United States
U.S./Israel
Israel 98/99/2000
Romania 1996
Europe/Russia
Italy 1998
Volgograd 1999
Israel 2000
India
India
Kunjin
Kunjin
1
Madagascar
Uganda 1937
Central African Republic
2
An exotic arbovirus in NYC was surprising
and unexpected:
Should it have been?
International Animal Importations
Into New York
August 1998 – July 1999
N = 2,873,144
Animals
none
1 – 6000
6001 - 20000
20001 - 50000
50001 - 350000
350001 -
Top Ten Countries of Origin
Passengers arriving into NY Airports
July 1998 – June 1999
N = 4,850,090
Country
DOMINICAN REPUBLIC
UNITED KINGDOM
CANADA
FRANCE
MEXICO
ITALY
JAPAN
BRAZIL
ISRAEL
BAHAMAS
GERMANY
BERMUDA
Passengers Percent
539,740
11%
456,540
9%
350,510
7%
312,400
6%
310,330
6%
215,040
4%
177,810
4%
157,220
3%
153,540
3%
143,390
3%
129,690
3%
114,750
2%
West Nile Virus Transmission Cycle
Mosquito vector
Incidental infections
West
Nile
Virus
West
Nile
Virus
Bird
reservoir
hosts
Incidental infections
West Nile Virus Amplification Cycle
Enzootic/epizootic
(amplifying) vectors
Incidental hosts
Humans
Horses
Other mammals
Culex pipiens
Cx. restuans
Cx. quinquefasciatus
Cx. tarsalis
?
Other mosquito vectors*
Amplifying hosts
Passerine birds
?
* With possible epidemic potential
Culex salinarius
Cx.nigripalpus
Ochlerotatus sollicitans
Oc. taeniorhynchus
Aedes vexans
Ae albopictus
West Nile Virus Ecology in North America,
as of Fall 2003
• 43 mosquito species
• 170 native and captive avian species
• Mortality varies greatly by species
• Very high viremias in some species
• Bird-to-bird transmission documented
• Virus in feces and oral swabs
• Oral infection possible
• 18 other species (e.g., cats, dogs, squirrels,
chipmunks, harbor seal, alligator, bats, reindeer)
WNV Surveillance
•
•
•
•
•
•
•
Dead birds (especially crows)
Human surveillance
Mosquitoes
Horse surveillance
Live captive sentinels (e.g. chickens)
Live wild birds
Zoo animals
States and Counties Reporting WNV
Activity, United States, 1999-2003*
Year
# States
# Counties
Date Range
1999
4
28
9 AUG – 15 NOV
2000
12**
145
6 FEB – 17 NOV
2001
27**
359
8 APR – 26 DEC
2002
44**
2,531
3 JAN – 19 DEC
2003
45
1,954
1 JAN –29-SEP
•Reported to ArboNET as of 09/03/2003
** Plus D.C.
Reported WNV Disease Cases in Humans,
United States, 1999-2003*
Year
# Cases
# States
1999
62
1
6
2 AUG – 24 SEP
2000
21
3
10
20 JUL – 27 SEP
2001
66
10
39
13 JUL – 7 DEC
2002
4,156
39**
740
19 MAY – 19 DEC
2003
5,722
41
730
28 MAR – 26 SEP
* Reported as of 09/30/2003
# Counties Onset Date Range
** Plus D.C.
Clinical Epidemiology
• Incubation period 2-14 days
• May be longer in immunosuppressed
• Approximately 20% mild febrile illness
• <1% severe neurological disease
• Meningitis, encephalitis, AFP
• Advanced age primary risk factor for encephalitis
• AFP patients may be younger
• Immunosuppressive drugs and hematological
malignancies risk factors
• Approximate 10% mortality
• Long-term morbidity common
WNV Human Infection “Iceberg” in 2002
284 fatalities
~ 3300 severe disease
~100,000
mild illness
~400,000
asymptomatic
<1%
CNS
disease
~20%
“West Nile Fever”
~80%
Asymptomatic
Month of Onset
De
c
Oc
t
pt
Se
Au
g
ly
Last Case
Dec 19
Ju
ne
Ju
Ma
y
l
Ap
ri
Ma
rch
Fe
b
1st Case
May 19
No
v
2200
2000
1800
1600
1400
1200
1000
800
600
400
200
0
Ja
n
# cases
Human WNV Illnesses (n=4156),
by Month of Symptom Onset, 2002
Human WNV Meningoencephalitis Incidence,
by Age Group, United States, 2002
Incidence per Million*
60
50
40
30
20
10
0
0-9
-19
0
1
-29
0
2
-3 9
0
3
-49
0
4
-59
0
5
-69
0
6
-79
0
7
-89
0
8
Age group (yr)
* States with human cases
-99
0
9
Fatality Rate among Persons with WNV
Meningoencephalitis, by Age Group, United
States, 2002
Fatality Rate (percent)
40
35
30
25
20
15
10
5
0
0-9
-19
0
1
-29
0
2
-3 9
0
3
-49
0
4
-59
0
5
-69
0
6
Age group (yr)
-79
0
7
-89
0
8
-99
0
9
Proportion of disease cases (%)
Human WNV Disease Cases, by Age Group and
Clinical Category, United States, 2003*
30
WNME
WNF
20
10
0
0 -9
-19
0
1
-29
0
2
-39
0
3
-4 9
0
4
-59
0
5
-69
0
6
Age group (yr)
* Reported as of 09/03/2003
-7 9
0
7
-89
0
8
-99
0
9
Novel Modes of West Nile Virus
Transmission, 2002
• Transplanted organs
• One donor to four recipients
• Transfused blood
• 23 confirmed cases in 2002, many more likely
• WNV screening began in July
• Breast milk
• One case, infant asymptomatic
• Transplacental transmission
• One case, severe outcome to infant
• Percutaneous, occupational exposure
St. Louis Encephalitis
• Related Japanese encephalitis serocomplex
flavivirus
• Endemic in the Americas
• Similar maintenance vectors
• Birds are main hosts
• Causes human epidemics
• Is SLE a model for the future behavior of WNV?
2500
Reported and Estimated Number of St. Louis
Encephalitis Cases, U.S., 1932- Sept 12, 2003
2000
1500
1000
500
0
1932
1942
1952
1962
1972
1982
1992
2002
Reported Number of West Nile Meningoencephalitis
Cases, U.S., 1932- Sep 30, 2003
2500
2000
1500
1000
500
0
1932
1942
1952
1962
1972
1982
1992
2002
SLE 1975
DC
Reported Incidence
in Humans:
SLE 1975
vs.
WNME 2002
WNME 2002*
Incidence per 106
>=10
1 – 9.9
0 – 0.9
* Reported as of 11/01/2002
DC
West Nile Virus Future in the United States
• Worrisome for several reasons
• Prolonged transmission season
• Wide geographic range
• Many potential amplifying avian hosts
• High viremias in birds
• Many potential mosquito vectors
• Many potential human-biting mosquito species
• Persistent infections in areas over 5 years
• Urban / suburban / rural transmission
JOIN THE
“SWAT TEAM”
AGAINST
WEST NILE VIRUS
Prevention
• Repellants
• DEET (up to 50% concentration); 10% in
children
• Permethrin on clothing and fabrics
• Reduce mosquito breeding sites
• Long sleeves and pants
• Stay indoors when mosquitoes are biting (dawn
and dusk)
• Bug zappers, sonic devices, CO2 devices
(mosquito magnet): no proven efficacy
Habitat elimination
Larviciding
Adulticiding
Документ
Категория
Презентации
Просмотров
7
Размер файла
8 172 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа