Theresa L. Smith, MD, MPHDivision of Vector-Borne Infectious DiseasesCenters for Disease Control and PreventionFort Collins, CO

West Nile Virus

Epidemiology & Surveillance Update 2005

Blood Product Advisory CommitteeGaithersburg, MDNovember 3, 2005

West Nile Virus (WNV) Update*West Nile Virus (WNV) Update*

• VirologyVirology

• Epidemiology of WNV in US 1999 – 2005 Epidemiology of WNV in US 1999 – 2005

• 2005 surveillance update2005 surveillance update

• Blood donation surveillance eventsBlood donation surveillance events

*Unless marked, all data including 2005 was in ArboNET as of 11/1/05*Unless marked, all data including 2005 was in ArboNET as of 11/1/05

WNV: Virology

• Flavivirus in the Japanese encephalitis serogroup• WNV & St. Louis encephalitis in the US

• Primarily bird pathogen• Bird – mosquito – bird transmission cycle

• Mammals are dead-end hosts in natural cycle• Low-level viremia before illness onset

WNV UpdateWNV Update

• VirologyVirology

• Epidemiology of WNV in US 1999 – 2005 Epidemiology of WNV in US 1999 – 2005

• 2005 surveillance update2005 surveillance update

• Blood donation surveillance eventsBlood donation surveillance events

ArboNET: A National Arbovirus Surveillance System

• Web-based passive system begun in 2000• 57 area health departments to DVBID

• Mosquito, bird, horse, other animal surveillance• Year, state, county, date of collection

• Human cases• Age, sex, race/ethnicity• Residence• Clinical illness, onset date and outcome• Blood or organ donation/receipt

First Reported WNV Activity, by State, 1999-2005

Human200120001999 2002

20032004

2004

2,539 human cases1,142 WNND100 deaths

40 states + DC523 counties

2005

2,581 human cases1,053 WNND83 deaths

40 states 563 counties

WNV UpdateWNV Update

• VirologyVirology

• Epidemiology of WNV in US 1999 – 2005 Epidemiology of WNV in US 1999 – 2005

• 2005 surveillance update2005 surveillance update

• Blood donation surveillance eventsBlood donation surveillance events

0

50

100

150

200

250

300

Week Ending

Nu

mb

er

of

ca

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s Onset Report

Human WNV Disease Casesby week of illness onset and date reported to ArboNET

United States, 2004

Reported Human WNV disease cases,United States, 1999-2005

Year Cases States/District

1999 62 1

2000 21 3

2001 66 10

2002 4,156 39 + DC

2003 9,862 45 + DC

2004 2,539 40 + DC

2005 2,581 42

Human WNV Disease, ArboNET 2005

2,581 case reports

• 42 states• Neuroinvasive – 1,053 • Fever – 1,363 • Deaths – 83*

• Median age: 78 yrs• Age range: 36 – 98 yrs

States with > 100 case reports

• California 824• Illinois 241• South Dakota 235• Texas 139 • Louisiana 111• Arizona 102

• 64% of all reports

* 78 fatalities had age available

WNV UpdateWNV Update

• VirologyVirology

• Epidemiology of WNV in US 1999 – 2005 Epidemiology of WNV in US 1999 – 2005

• 2005 surveillance update2005 surveillance update

• Blood donation surveillance eventsBlood donation surveillance events

WNV Blood Screening, US, 2003-2005

Year Screened* PVDs WNND WNF TAT

2003 6.2 818 6 137 6

2004 8.2 224 4 66 1

2005 NA 374 3 82 1

*In millions

Data

unavailable

Reported PVDs to ArboNET, 2004 vs. 2005

2004• 224 in 29 states

• Top four states:• California 66• Arizona

36• Colorado 24• Texas 16

2005• 374 in 30 states

• Top four states:• California 87• Texas 57• Nebraska 53• Louisiana 22

Implicated Donation Viral Concentrations

• 2002• 16 implicated donations had virus titers ranging from

0.8 to 75.1 pfu/mL with a of median of 10.5 pfu/mL

• 2003• Four implicated donations had virus titers ranging from

0.06 to 0.5 pfu/mL with a median of 0.11 pfu/mL

• 2004• One implicated donation had a viral titer of 0.12 pfu/mL

2005 Investigations

• Blood Transmission

• 6 investigations

• 3 negative

• 3 pending plasma return from Switzerland

• Organ Transplantation Transmission

• Likely mosquito-borne infection in donor

• Possible febrile illness

• IgM positive, PCR negative before donation

• Three of four organ recipients PCR positive

• Two became ill

Organ Donor TimelineAugust 2005

Serum, PlasmaPCR (-)

IgM, IgG (+)

28

WNV +MosquitoesIn Nearby

ParkInjury andSurgery

Organ Recovery

BrainDeath

262316

Febrile Illness?

27

2005 Summary

• WNV activity over most of the continental US• Continued westward expansion

• Full season of transmission in CA• Human cases reported from all states except

Alaska, Hawaii, Maine, & Washington• Risk of WNV TAT unknown• Continue to investigate possible TAT• TAT less likely to cause organ transplant related

WNV transmission