Update on West Nile Virus – United States, 1999-2006

Eileen C. Farnon, MD

Arboviral Diseases Branch

Division of Vector-Borne Infectious Diseases

Centers for Disease Control and Prevention

Fort Collins, Colorado

Blood Products Advisory Committee

89th Meeting

April 27, 2007

WNV Transmission Cycle

Enzootic (Maintenance/Amplification)

Epizootic

Epidemic

Amplifying hosts

Dead-end hosts (usually)

ArboNET

• Arboviral national electronic surveillance system• Humans • Ecologic• Mosquitoes• Birds• Animals• WNV, SLE, EEE, WEE, LAC, DEN, VEE

• All data current as of April 12, 2007

Human WNV Syndromes Reported to ArboNET

• WN fever (WNF)

• WN neuroinvasive disease (WNND)

• Meningitis

• Encephalitis

• Acute flaccid paralysis

• Other

• Unspecified illness

Incidence per million

.01-9.99 10-99.99 >=100 Any WNV Activity

WNV Neuroinvasive Disease Incidence, by County, US, 1999

N=59

WNV Neuroinvasive Disease Incidence, by County, US, 2000

Incidence per million

.01-9.99 10-99.99 >=100 Any WNV Activity

N=19

WNV Neuroinvasive Disease Incidence, by County, US, 2001

Incidence per million

.01-9.99 10-99.99 >=100 Any WNV Activity

N=64

WNV Neuroinvasive Disease Incidence, by County, US, 2002

Incidence per million

.01-9.99 10-99.99 >=100 Any WNV Activity

N=2,946

WNV Neuroinvasive Disease Incidence, by County, US, 2003

Incidence per million

.01-9.99 10-99.99 >=100 Any WNV Activity

N=2,866

WNV Neuroinvasive Disease Incidence, by County, US, 2004

Incidence per million

.01-9.99 10-99.99 >=100 Any WNV Activity

N=1,148

WNV Neuroinvasive Disease Incidence, by County, US, 2005

Incidence per million

.01-9.99 10-99.99 >=100 Any WNV Activity

N=1,309

WNV Neuroinvasive Disease Incidence, by County, US, 2006

Incidence per million

.01-9.99 10-99.99 >=100 Any WNV Activity

N=1,491

*Reported as of 4/12/2007

Onset of Human WNV Disease,United States 1999-2006*

*Reported as of 4/12/2006

1999

2000

2001

2002

2003

2004

2005

2006

2007Jan

FebM

arApr

May

JunJul

AugSep

OctNov

Dec

Month

Cumulative WNND Incidence, by County, US, 2002-2006

*Reported as of 11/14/06Lindsey N, et al, in press

0

50

100

150

200

250

300

0 50 100 150 200 250 300 350 400 450 500Cumulative Incidence Rank

Med

ian

An

nu

al In

cid

ence

Ran

k

Top 5% Ranks Top 10% Ranks Top 20% Ranks

Median Annual WNND Incidence Rank versus Cumulative WNND Incidence Rank by County, 2002-2006

*Reported as of 11/14/06Lindsey N, et al, in press

Counties with Persistently High WNND Incidence, 2002-2006

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

Year Total WNND WNF/other Deaths

1999-2001 149 142 7 18

2002 4,156 2,946 1,210 284

2003 9,862 2,866 6,996 264

2004 2,539 1,148 1,391 100

2005 3,000 1,309 1,691 119

2006 4,261 1,491 2,770 176

Total 23,967 9,902 14,065 961

*Reported as of 4/12/2007

WNV Blood Screening

• 2002 – 23 cases of transfusion-associated transmission (TAT)

• 2003 – Nucleic acid amplification tests (NAT)

• MP-NAT (6-16 units) ID-NAT

• Blood banks report presumptively viremic donors (PVDs) to local public health department

• Remove infectious blood products from circulation

• Public health departments report to ArboNET

• Perform clinical follow-up

• Perform trace-back investigations

WNV PVDs by Year*

Year PVDs

2003 818

2004 224

2005 417

2006 361

Total 1820

*Reported as of 4/12/2007

West Nile Viremic Blood Donors, by State of Residence, 2006*

*Reported as of 4/12/2007

PVDs Reported to ArboNET*, 2006

• Over 8 million donations screened

• 361 PVDs reported to ArboNET

• 84 (23%) WNF

• 4 (0.1%) WNND

• 2 (0.1%) other

• 118 (33%) reported from 3 states: NE, ID, TX

*Reported as of 4/12/2007

WNV Transfusion-associated Transmission, 2006 – Case 1

• 82 y male resident of SD recently post-kidney

transplant

• 4d post-transplant: 2U PRBC

• 21d post-transplant: encephalitis

• WNV IgM detected in serum and CSF

• Organ donor tested negative for WNV

• Blood donor tested positive for WNV IgM

• negative MP-NAT

MMWR 2/2/07

WNV Transfusion-associated Transmission, 2006 – Case 2

• 60 y male resident of IA 5y post-kidney

transplant

• Spinal fracture repair in SD: 15 blood

products

• 6U FFP from blood donor

• 11d post-operatively: encephalomyelitis

• WNV IgM detected in CSF

MMWR 2/2/07

Summary

• WNV occurs throughout the continental U.S.

• Western plains have highest incidence of WNND

• Dates of onset for WNV disease span the year

• 2 cases of transfusion-associated transmission

despite MP-NAT testing

• New approaches to triggering ID-NAT considered

Acknowledgements

The findings and conclusions in this presentation are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention.

• Jennifer Lehman• Nicole Lindsey• Stephanie Kuhn• Margaret Collins• Kate Ellingson• Matt Kuehnert• Mark Duffy• Marc Fischer• Edward Hayes• John Jones• Nicholas Komar

• Roger Nasci• John Roehrig• Janet McAllister • Harry Savage• James Sejvar• Theresa Smith• Grant Campbell• Brad Biggerstaff• Lyle Petersen• All reporting states,

jurisdictions, and local health departments

Photo: Meggan Gould

Cumulative Incidence of WNND by State – United States, 2002-2006*

*Reported as of 11/14/06