workshop on west nile virus berlin, 13th -17th of … nile epidemiology:global situation and recent...

Workshop on West Nile virusBerlin, 13th -17th of February, 2012

West Nile epidemiology:global situation and recent

outbreaks in Europe

Tamás Bakonyi1, Norbert Nowotny2

1 Department of Microbiology and Infectious Diseases, Faculty of Veterinary Science, Szent István University, Budapest, Hungary2Zoonoses and Emerging Infections Group, Clinical Virology, Department of Pathobiology, University of Veterinary Medicine, Vienna, Austria

West Nile epidemiology:global situation and recent outbreaks in Europe

• virology

• transmission cycle

• epidemiology and distribution

– West Nile lineages

– the emergence of WNV in the USA

– the European scenario

West Nile epidemiology: global situation and recent outbreaks in Europe

Virology

• West Nile virus (WNV)

– Flaviviridae, Flavivirus, mosquito-borne group,• Japanese encephalitis virus serocomplex

• +ssRNA genome, ~ 11,000 base

• 3 structural and 7 non-structural proteins

• stem-loop structures at the UTR regions

• icosahedral capsid

• enveloped

• relatively weak resistance (heat, detergents)

• strong antigen

– the E glycoprotein is the neutralizing Ag

– one serotype

– cross-reactions with other flaviviruses

West Nile epidemiology: global situation and recent outbreaks in Europe

5’- -3’

C M E NS1 NS2ANS2B

NS3 NS4ANS4B

NS5

West Nile epidemiology: global situation and recent outbreaks in Europe

Transmission cycle• natural host of WNV are wild birds

– several species are susceptible

• USA: 371 bird species

– frequent subclinical infections

• varying length of viraemia

• varying level of virus titre in the blood (amplifying host)

• transient shedding with faeces and body fluids

– certain species are more vulnerable

• USA: 62% of the WNV positive dead birds were American crows and Blue jays

• main vectors are mosquitoes

– several species are potential carriers

• USA: 62 WNV positive mosquito species reported

• >98% of the positive pools are of Culex spp.

• in Europe the principal vector is usually Culex pipiens

– ornithophillic

– overwinters in adult form

– gradation in late summer and autumn

• the extrinsic period is significantly influenced by the weather

Kilpatrik et al., PloSPath. 2008. 4/6, e10000092

infected mosquitoes

disseminated infection in mosquitoes

transmitting mosquitoes

days after feeding

ratio

West Nile epidemiology: global situation and recent outbreaks in Europe

Transmission cycle• natural host of WNV are wild birds

• main vectors are mosquitoes

• tick are also potential vectors

• several other vertebrates are susceptible hosts

– mammals (humans, horses), reptiles (alligators), amphibians (frogs)

– incidental hosts – the mosquitoes’ choice

– dead-end hosts – viraemia is lower than the mosquito infection threshold

• possible non-vectorial transmission

– iatrogenic – blood transfusion, organ transplantation

– intrauterine, lactogenic – reported in humans

– accidental – necropsy, laboratory infections

– peroral

• scavenger birds – carrion feeding (i.e. craws)

• birds of prey (i.e. goshawks)

• virus shedding by faeces (common coots?)

West Nile epidemiology: global situation and recent outbreaks in Europe

West Nile epidemiology: global situation and recent outbreaks in Europe

Epidemiology and distribution– first isolation: West Nile district of Uganda, 1937

• from a febrile woman

– the most widespread flavivirus

• Africa, Europe, Asia, Australia (Kunjin), North and South America

• WNV lineages

– Two main genetic lineages

• lineage 1: word-wide distributed

– topotype strain: Eg101 (Egypt, 1951)

– three clades (~ geographic distribution)

– virulence – variants

• lineage 2: limited distribution

– topotype strain: B956 (Uganda, 1937)

– Sub-Saharan Africa and Madagascar

– strain Q3574-5 isolated in 1968 from a migrating Barred Warbler (Sylvia nisoria) on Cyprus (Watson et al. 1972)

Lanciotti et al.Virology 298, 96-105 (2002)

West Nile epidemiology: global situation and recent outbreaks in Europe

Epidemiology and distribution

• WNV lineages

– Two main genetic lineages

• lineage 1: word-wide distributed

• lineage 2: limited distribution

– topotype strain: B956 (Uganda, 1937)

– Sub-Saharan Africa and Madagascar

– emergence in central Europe (Hungary) in 2004

– emergence in Russia (Volgograd) in 2007

– differences in virulence!

– Further genetic lineages

• lineage 3: Rabensburg strain

– first isolation in the Czech Republic, from Cx. pipiens

– reisolation in 1999 (Cx. pipiens) and in 2006 (Ae. rossicus)

– no Rabensburg strain associated cases reported in the area

– limited pathogenicity in mice

West Nile epidemiology: global situation and recent outbreaks in Europe

Epidemiology and distribution

• WNV lineages

– Two main genetic lineages

• lineage 1: word-wide distributed

• lineage 2: limited distribution

– Further genetic lineages

• lineage 3: Rabensburg strain

• lineage 4: LEIV-Krnd88-190

– isolated in Russia (Caucasus) in 1998

– isolated from ticks (Dermacentor marginatus)

– virulence is unknown

Lineage 1

Lineage 2

Putative Lineage 3

Putative Lineage 4

1a

1b

West Nile epidemiology: global situation and recent outbreaks in Europe

Epidemiology and distribution

• WNV lineages

– Two main genetic lineages

• lineage 1: word-wide distributed

• lineage 2: limited distribution

– Further genetic lineages

• lineage 3: Rabensburg strain

• lineage 4: LEIV-Krnd88-190 (Lvov et al., 2004)

• lineage 5: Indian isolates (Bondre et al., 2007)

• lineage 6: Malaysian isolate (Scherret et al., 2001)

• lineage 7: Spanish isolate (Vazquez et al., 2010)

Bondre et al., J. Gen. Virol. 88:875-84 (2007)

Vazquez et al., 2010. Emerg Infect Dis., 16.: 549-552.

West Nile epidemiology: global situation and recent outbreaks in Europe

Epidemiology and distribution

• The emergence of WNV in the USA

– New York (Queens, Bronx) – 1999

• encephalitis in humans, horses, dogs and cats

• wild bird mortality

• identification of the agent – WNV lin. 1

• genetic characterisation – close relationship with an isolate from Israel (1998)

• the route of introduction remained unknown

– The virus established itself in the new habitat and quickly spread westwards

WNV Neuroinvasive Disease Incidence, by County, US, 1999

Incidence per million.01-9.99

10-99.99

>=100

Any WNV activity

N=54

L. Petersen, CDC

Incidence per million.01-9.99

10-99.99

>=100

Any WNV activity

WNV Neuroinvasive Disease Incidence, by County, US, 2000

N=19

L. Petersen, CDC

Incidence per million.01-9.99

10-99.99

>=100

Any WNV activity

WNV Neuroinvasive Disease Incidence, by County, US, 2001

N=64

L. Petersen, CDC

Incidence per million.01-9.99

10-99.99

>=100

Any WNV activity

WNV Neuroinvasive Disease Incidence, by County, US, 2002

N=2946

L. Petersen, CDC

Incidence per million.01-9.99

10-99.99

>=100

Any WNV activity

WNV Neuroinvasive Disease Incidence, by County, US, 2003

N=2866

L. Petersen, CDC

WNV Neuroinvasive Disease Incidence, by County, US, 2004

Incidence per million.01-9.99

10-99.99

>=100

Any WNV activity

N=1142

L. Petersen, CDC

WNV Neuroinvasive Disease Incidence, by County, US, 2005

N=1294

Incidence per million.01-9.99

10-99.99

>=100

Any WNV activity

L. Petersen, CDC

WNV Neuroinvasive Disease Incidence, by County, US, 2006

N=1495

Incidence per million.01-9.99

10-99.99

>=100

Any WNV activity

L. Petersen, CDC

2002

2001

2002

2002 2002

2002

2004

2004

2003

West Nile Virus in Latin America

2004

2003

•2003

2004

2003

2004

2006 ArgentinaL. Petersen, CDC

Human WNV Disease Casesby Week of Onset, United States, 2006*

050

100150200250300350400450500550600

7-Ja

n21

-Jan

4-Fe

b18

-Feb

4-M

ar18

-Mar

1-Apr

15-A

pr29

-Apr

13-M

ay27

-May

10-J

un25

-Jun

8-Ju

l22

-Jul

5-Aug

19-A

ug2-

Sep

16-S

ep30

-Sep

14-O

ct28

-Oct

11-N

ov25

-Nov

9-Dec

23-D

ec

Week ending

# ca

ses

* Reported as of 5/2/2007, courtesy L. Petersen

Reported Human West Nile Virus Casesby Date of Symptom Onset; and Date of First Positive Surveillance Event,

Colorado, 2003

0

10

20

30

40

50

60

70

80

90

100

110

06-jú

n-03

20-jú

n-03

04-jú

l-03

18-jú

l-03

01-a

ug-03

15-a

ug-03

29-a

ug-03

12-sz

ept-0

3

26-sz

ept-0

3

10-o

kt-03

24-o

kt-03

Symptom onset date

No.

of

case

s

Fever(n=2323)Neuroinvasive(n=621)mosquito

human

chicken

bird

horse

Source: John Pape, CO DOH

0

2000

4000

6000

8000

10000

12000

14000

16000

1999 2000 2001 2002 2003 2004 2005 2006

0

500

1000

1500

2000

2500

3000

3500

4000

Equine

Human

Equine and Human WNV NeuroinvasiveDisease Cases, United States, 1999-2006

Total Equine: 24,213 cases

Total Human: 9,906 cases

Eq

uin

e C

ase

Rep

ort

s Hu

man

Case R

epo

rts

Vaccine introduced

Reported WNV Disease Cases in Humans,United States, 1999-2006*

YearTotal

WNNDFever

Other

clinical/

Unspec

Total cases

Deaths

1999 59 3 0 62 7

2000 19 2 0 21 2

2001 64 2 0 66 9

2002 2,946 1,160 50 4,156 284

2003 2,866 6,830 166 9,862 264

2004 1,148 1,269 128 2,539 100

2005 1,309 1,607 99 3,000 119

2006 1,495 2,616 194 4,269 177

Total 9,906 13,489 637 23,975 962

* Reported as of 5/2/2007, courtesy L. Petersen

Clinical manifestation of WNV in the USA

• Asymptomatic (approx. 75%)

• West Nile fever (approx. 25%)

• Neuroinvasive disease (approx. 1/140)

– Encephalitis

– Meningitis

– Flaccid paralysis

Courtesy L. Petersen, CDC

Asymptomatic

1,040,300

Fever

322,800

Fever

13,484

Neuroinvasive,

Non-fatal

8,942

Fatal, 962

Reported

The Hidden EpidemicWNV Infections (n=1.4 million), 1999-2006

Not reported

Courtesy L. Petersen, CDC

WNV epidemiology and distributionThe European scenario

• First detection:– Albania 1958 (serology)

• Virus isolation:– France, Russia, Portugal

Slovakia, Moldavia,Ukraine, Hungary,Romania, Czech Rep.,Italy

• Cases, outbreaks:– 1960’s:

France, Russia, Spain, Romania

– 1970-90’s:Byelorussia, Ukraine, Romania, Czech Republic

Hubalek & Halouzka, 1999

virusisolationcase

seropositivity

Zeller & Schuffenecker, 2004

• 2003, France: horse, magpie

• 2002-2007, Spain: imperial eagle (Aquila adalberti)

• 2006-2007, Germany, Poland: seropositive birds

Rather widespread WNV outbreak in summer 2008 in northern Italy

G. Savini et al., 2008, Eurosurveillance

G. Savini et al., 2008, Eurosurveillance

WNV in Hungary

• Serological studies (1969): wild geese, humans

• Isolation (1970’s): bank vole, yellow-necked mouse

→ no documented clinical case

• 2003:

– Goose encephalitis• Great Plain, middle of August

• 6 week-old goslings, 14% mortality

• seroconversion, PCR positivity

• Lineage 1 WNV strain

– Sporadic human meningitis, encephalitis• Great Plain, end of summer – fall

• seroconversion

• 2004-2005:

– encephalitis cases in birds of prey• Körös-Maros National Park

• goshawk, sparrow-hawk; CNS symptoms, mortality

• Lineage 2 WNV strain!

– sheep encephalitis, death• the virus is > 99% identical with the goshawk strain

• 2007:

– mortality in geese

– horse encephalitis

– mortality in birds of prey (goshawk, red-footed falcon)

– human cases

• 2008

– wild bird, hhorse and human cases

– significant geographic sperad

– emergence in Austria

• 2009 – 2011

– WNV activity in the affected areas in every epidemic season

WNV-cases 2004

WNV-cases 2004-2005

WNV-cases 2004-2005-2007

WNV-cases 2004-2005-2007-2008

WNV-cases 2004-2005-2007-2008-2009

WNV-cases 2004-2005-2007-2008-2009-2010

WNV-cases 2004-2005-2007-2008-2009-2010-2011

WNV situation in 2010 in Europe

WNV situation in 2010 in Europe

• northern Greece– August - October 2010

– a widespread WNV outbreak involving mainly humans

– approx. 250 human cases, 191 neuroinvasive, 32 lethal

– Whole genome sequencing revealed the Hungarian / Austrian lineage 2 WNV causing the outbreak in Greece

– however, with a possibly important aa mutation

• Russia – Volgograd region– in summer / autumn 2010

– a widespread WNV outbreak with ~ 231 reported human cases and 6 deaths

– aetiological virus seems to be identical to the one, which caused the 2007 Volgograd outbreak

– a lineage 2 virus, different from the Hungarian/Austrian/Greek one

Papa et al., Clin. Microbiol. Infect., in press

Histidine→ Proline

WNV situation in 2010 in Europe

• northern Greece

• Russia – Volgograd region

• Romania

– ~ 50 reported human cases

– in 2 human samples a lineage 2 WNV is diagnosed

– practically identical with the Volgograd strain

• Serbia (Novi Sad)

– WNV detection in Cx. pipiens pools

– > 99% identity with the Hungarian / Austrian / Greek strain

Human West Nile Disease cases, Romania 2010[Sirbu et al., Eurosurveillance 16 (2), 13 January 2011]

WNV situation in 2011 in Europe

• Ancona, North-East Italy

– WNV detection in a febrile patient

– partial sequence identification

– > 99% similarity to the Hungarian / Austrian / Greek lineage 2 strain

West Nile epidemiology: global situation and recent outbreaks in Europe

Conclusions

• WNV is a significant human and animal pathogen

• increased WNV activity was observed in Europe since 2008

• exotic (lineage 2) strains emerged and are spreading in the continent

• endemic (lineage 1 and 3) strains are also present

• the virus activity is influenced by the weather

• the circulating strains differ in neurovirulence

→ Diagnostic difficulties

→ Necessity of monitoring and surveillance activity

Acknowledgements:

Jolanta Kolodziejek Zoonoses and Emerging Infections Group, Clinical Virology, Department

Helga Lussy of Pathobiology, University of Veterinary Medicine, Vienna, Austria

Bernhard Seidel Office of Ecology Research and Landscape Assessment, Persenbeug,

Austria

Éva IvanicsKároly Erdélyi Central Veterinary Institute, Budapest, Hungary

Krisztina Ursu

Emöke Ferenczi National Center for Epidemiology, Budapest, Hungary

Orsolya Kutasi Large Animal Clinic, Faculty of Veterinary Science, Szent István

University, Üllő, Hungary

Herbert Weissenböck Institute of Pathology and Forensic Veterinary Medicine, Department

of Pathobiology, University of Veterinary Medicine, Vienna, Austria

Katharina Brugger Institute of Veterinary Public Health, University of Veterinary

Medicine, Vienna, Austria

EDENext and Vectorie EU FP7 projects