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West nile virus: spread, epidemiology, ecology

Geog 380, Spring 2011

Objectives

Describe the sequence of events of WNV;

Understand the epidemiology/ecology of WNV;

Analyze the spatial (geographic) spread of WNV

Fit West Nile into the “Factors of Emergence”

framework

The sequence of events (described well in Drexler)

Source: Google Earth, accessed 4/20/10

Source: Google Earth, Accessed 4/20/10

Hospital admissions and initial detection

Series of patients admitted to Flushing Hospital

AUG 12:

60 year old gentleman

History of fever, weakness, nausea x 1 wk.

Hospital course:

Confusion, proximal (near the body) muscle weakness, urinary retention, respiratory insufficiency

Intubated and put on ventilatory support

(cont)

AUG 15- 80 y/o man

1 week history of fever, headache, weakness, diarrhea

Developed flacid paralysis

Died

AUG 18-SEPT 2

4 more patients—encephalitis

2 patients--meningitis

Published in Clinical Infectious Diseases, 2000;30:413-8

“This outbreak emphasizes the important relationship veterinarians, physicians, and the public health structure should have in the surveillance of disease.” Asnis et al, in Clinical Infectious Diseases, 2000;30:413-8

Full epidemiologic investigation

Identify patients

Look for common behaviors/exposures

Map/analyze spatially

Risk factors (case-control)

New syndrome

Reactions

Spraying

Warnings to public

Risk communication

Social amplification of risk

Not newsy any more

Lots of people even think that WNV is gone!

Genome sequenced (RT-PCR)

Lipkin lab: Jia et al, Lancet 1999;354:1971-2

From Kramer et al, Annu Rev Entomol, 2008;53:61-81

West Nile Virus Incidence

Rate by Year

Source: Sugumuran et al,

Int J Health Geographics

2009

West Nile Neuro-

Invasive Incidence

Rate, 2000

Source: MMWR,

July 9, 2009

http://westnilemaps.usgs.gov/us_human.html

Source:

Source: Petersen and Hayes, Med Clin North. Am, 2008,

Migratory

Birds

Source:

Gubler, CID,

2007

Iwamoto et al., New England Journal of Medicine, 2003;348:2196-2203