Transcript Document

West Nile Virus
Focus on clinical aspects of
human infection
Jo Hofmann, MD
State Epidemiologist for
Communicable Disease
Washington State Department of Health
Overview and learning objectives
• Review:
 Clinical features of human West Nile virus
(WNV) infections
 Routes of WNV transmission in humans
• Learning objectives
 Describe symptoms of the most common
illness associated with WNV infection
 Identify the most common route of virus
transmission
 Describe two new methods of surveillance
for WNV infections
Washington State
Department of Health
WNV infection: clinical syndromes
• West Nile fever
 Mild infection
• West Nile neuroinvasive disease
 Meningitis
 Encephalitis
 Acute flaccid paralysis (AFP)
Polio-like syndrome
 Movement disorders
Involuntary muscle spasms
Parkinson’s-like syndromes
 Other neurological manifestations
Washington State
Department of Health
Human infection with WNV
1/150 of all infections
cause West Nile
neuroinvasive
disease (WNND)
<1%
WNND
~20%
West Nile fever
Fatal WNV infection:
<0.1% of all infections
10% of WNND
Very crude
estimates
~80%
No symptoms
Washington State
Department of Health
West Nile virus infections, by age group
& clinical category -- United States, 2003
Incidence per 100,000
5
West Nile Neuroinvasive Disease
West Nile Fever
4
3
2
1
0
0-9
9
9
9
9
9
9
9
9
9
1
2
3
4
5
6
7
8
9
10
20
30
40
50
60
70
80
90
Age group (yr)
Source: Hayes, N. 5th Nat’l Conf. on West Nile Virus, 2004
Washington State
Department of Health
West Nile fever
• Self-limited illness with sudden onset




Fever, headache, muscle aches, fatigue
Nausea, vomiting
Rash, swollen lymph nodes
Symptoms can be debilitating, may
persist for weeks
• Does not progress to West Nile
neuroinvasive disease
Washington State
Department of Health
West Nile neuroinvasive disease
• The disease formerly known as West Nile
meningoencephalitis
• Rarest WNV infection
• Neurological symptoms occur 1-2 days after
onset of fever
• WNND includes
 Meningitis - stiff neck, headache, abnormal
cerebrospinal fluid
 Encephalitis - confusion, seizures
 Acute flaccid paralysis (AFP)
Washington State
Department of Health
West Nile virus-associated
acute flaccid paralysis (AFP)
• Rare, cases seen during outbreaks
• Symptoms look like poliomyelitis (polio)
 Asymmetrical weakness (left > right, etc.)
 No sensory symptoms
 Abnormal cerebrospinal fluid
• Affects young, healthy patients compared
with other WN neuroinvasive disease
• Fever, headache may be absent
• May occur with or w/o meningitis or
encephalitis
Washington State
Department of Health
Dude,
where’s my
blood meal?
Newly described
routes of WNV transmission
• Transfusion of blood, platelets, fresh frozen
plasma
• Organ transplantation
• Perinatal exposure (infected mother to
newborn)
• Breastfeeding
• Occupational exposure (laboratory
accidents, alligator and poultry farming)
Washington State
Department of Health
WNV infections
following transfusion
• First recognized in 2002
• >60 suspected cases investigated; 23 cases
confirmed following transfusion from 16
infected donors
• Sources: red blood cells, platelets, and
plasma
• Nationwide screening of blood donations
began July 2003 – new method of
surveillance for WNV infections
Washington State
Department of Health
Screening the blood supply
• Asking donors about symptoms
• Screening donations with nucleic acid
amplification test (NAAT) – detects virus
• Contaminated products destroyed, donors
contacted
• Blood banks report infected blood products
to state health departments
• 6.2 million units screened in 2003 – >1000
donors infected with WNV reported
Washington State
Department of Health
Confirmed and probable
transfusion-associated WNV infection, 2003
• Occurred in epicenter of outbreak
 Three in Texas
 One each in Nebraska, Iowa, Kansas
• Onset of symptoms during peak of
outbreak: August through October
• Average age of cases 63 years
• Five developed WNND (encephalitis)
Washington State
Department of Health
Perinatal
transmission of WNV
• First described in U.S. in 2002
• Several children born to mothers with
confirmed WNV infection
 Some with neurological defects
• A large series of cases from 2003-2004
still being investigated
• CDC has on-line reporting site for
registry of pregnancy-associated cases
Washington State
Department of Health
Contents
MMWR 2001;50:343-5
West Nile Virus
Questions and
Answers
West Nile Virus Home >West Nile Virus infection acquired during pregnancy
West Nile virus disease during pregnancy
In 2002, the Centers for Diseases Control and Prevention
(CDC) Division of Vector-Borne Diseases (DVBID) published
the first report of intrauterine WNV transmission, in which
the infant had congenital abnormalities (MMWR
2001;50:343-5). This single case does not provide proof of a
causal relationship between WNV infection during
pregnancy and such abnormalities. The CDC is enhancing
surveillance to learn more about intrauterine WNV
transmission and birth outcomes. Healthcare providers and
state and local health departments are encouraged to report
cases of known or suspected WNV disease (WN fever or
meningoencephalitis) during pregnancy.
Health Care Providers: to report a case of WNV disease during
pregnancy, please call 970-266-3525 or send us your contact
information in the box provided below. We will contact you promptly.
Please do not submit confidential patient information. Note: Because
local health professionals need to be involved in the evaluation, reports
cannot be accepted directly from individual patients.
Coming soon: web-based
reporting WNV infection
during pregnancy:
Healthcare providers report online
States/local HD informed when
their providers report
Providers contacted for follow-up
and specimens needed for testing
For now:
Your Name:
Call state/local health department
or CDC @ 970-221-6400
Your Phone
Number
(including area
code):
Best Time to
call:
Comments
Submit
Summary
• Most WNV infections are asymptomatic
• Most common illness is West Nile fever
• The most common route of transmission is
through the bite of an infected mosquito
 Transfusion and pregnancy associated cases
• Screening of blood donors and web-based
reporting of pregnancy associated cases are
new surveillance methods
Washington State
Department of Health
Questions?
References
• Interim guidelines for the evaluation of infants born to
mothers infected with West Nile virus during pregnancy.
MMWR 2004;53:154-7
• Transmission of West Nile virus from an organ donor to
four transplant recipients. New Engl Jour Med
2003;348:2196-2203.
• Possible West Nile virus transmission to an infant
through breast-feeding - Michigan 2002.
MMWR 2002; 51:877-8.
Washington State
Department of Health
References
• Petersen LR, Marfin AA. West Nile Virus: a primer for
the clinician. Ann Intern Med 2002;137:173-9.
• Investigations of West Nile virus infections in recipients
of blood transfusions. MMWR 2002;51:973-4.
• Neurologic manifestations and outcome of West Nile
virus infection. JAMA. 2003;290:511-5.
• CDC WNV clinical guidance website:
http://www.cdc.gov/ncidod/dvbid/westnile/clinical_guidance.htm
Washington State
Department of Health