VIRAL ZOONOSES

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VIRAL ZOONOSES

• ZOONOTIC VIRUSES
• TRANSMISSIBLE FROM ANIMALS
• ARTHROPODS
• often via a blood sucking arthropod
• VERTEBRATES
• bites, body fluids, inhalation etc

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VIRAL ZOONOSES

• PART I
• ARTHROPOD BORNE

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transmission

• arthropod vectors (blood sucking)
• Many arboviral diseases world wide (hundreds)

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VIGILANCE
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• ARBOVIRUSES
• FEBRILE DISEASES
• ENCEPHALITIS
• HEMORRHAGIC FEVERS

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ARBOVIRUSES
FAMILY
ENVELOPE yes yes no
SYMMETRY icosahedral helical icosahedral
GENOME ssRNA (ve) ssRNA (-ve) segmented dsR
NA, segmented
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Birds Mammals Humans
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• ARTHROPOD
• Habitat
• Diurnal activity
• Preferred host
• Annual activity
• Overwintering ability
• Transovarial transmission

• VERTEBRATE
• Migratory activity
• Persistence of viremia
• Clinical consequences
• Reservoir ?
• Dead end host?

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PREVENTION

• SURVEILLANCE
• VECTOR CONTROL
• REPELLENTS
• CLOTHING
• TIMING OF ACTIVITY (OR CANCELLATION)
• VACCINE

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SYLVATIC (JUNGLE) CYCLE
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URBAN CYCLE
human cycle
note viruses which have a human cycle may also
have a sylvatic/jungle cycle
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OUTBREAKS

• TEND TO BE SUMMER/EARLY FALL
• SPORADIC
• UNPREDICTABLE

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ARBOVIRAL DISEASE

• MANY DIFFERENT ARBOVIRUSES CAUSE DISEASE
• OFTEN SUB-CLINICAL

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ARBOVIRAL DISEASE

• INITIAL VIRAL REPLICATION
• endothelial cells
• macrophages/monocyte lineage
• INTERFERON (RNA VIRUSES)
• headache, fever, myalgia
• VIREMIA

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RECOVERY

• INTERFERON
• CELL-MEDIATED IMMUNITY
• ANTIBODY MAY PLAY A ROLE IN PREVENTING SPREAD
  DURING VIREMIC PHASE

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DIAGNOSIS

• Immunological techniques
• RT-PCR for viral RNA

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RESISTANCE

• IgG

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ARBOVIRUSES ENCEPHALITIS
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ARBOVIRUS ENCEPHALITIS

• SPORADIC
• LOW INFECTIONS -gt CLINICAL CASES
• NOT ALL CASES -gt MAJOR DISEASE
• PROBABLY UNDERDIAGNOSED

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WEST NILE VIRUS

• Reservoir birds
• Vector mosquito

flavivirus
http//www.cdc.gov/ncidod/dvbid/westnile/cycle.htm
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flavivirus
West Nile virus
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WEST NILE VIRUS

• Symptoms
• Fever
• Meningitis
• Encephalitis
• More rarely
• Acute flaccid paralysis
• West Nile polio-like paralysis
• poliomyelitis - inflammation spinal cord

flavivirus
http//www.cdc.gov/ncidod/dvbid/westnile/cycle.htm
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West Nile Virus

• For every 150 people infected
• 30 mild symptoms
• mild fever, headache, body ache, maybe rash
• may never see physician, even if do, may not be
  diagnosed
• 1 severe illness
• e.g. encephalitis, meningitis, high fever, stiff
  neck, stupor, disorientation, coma, tremors,
  convulsions, muscle weakness
• frequency of flaccid paralysis unknown, but much
  less than frequency of encephalitis

flavivirus
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WEST NILE VIRUS

• Case fatality ratio
• Seen in all age groups but higher in the elderly
• the majority of cases of neuroinvasive diseases
  and fatalities are over 50 yrs age
• Transplant recipients may be at higher risk
• increased incidence of clinical disease
• increased risk of severe disease

flavivirus
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http//www.cdc.gov/ncidod/dvbid/westnile/resources
/wnv_transplant20brochure6_12_07.pdf
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WEST NILE VIRUS

• transmission
• Mosquito (vast majority of cases)
• Blood transfusion (blood supply is now screened)
• Organ donation

flavivirus
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flavivirus

• Reported Human WNV Disease Cases, US
• 1999 62
• 2000 21
• 2001 66
• 2002 4156
• 2003 9862
• 2004 2539
• 2005 3000
• 2006 4269
• 2007 3630

2007 Case Fatality Rate 124/3630 3.4
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ST. LOUIS ENCEPHALITIS

• Second commonest mosquito borne disease in US
• Reservoir birds
• Man is usually a dead end host
• Vector mosquito
• lt1 infections clinical
• Elderly at higher risk
• CFR 3-25
• 100 cases/year av.

flavivirus
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EASTERN EQUINE ENCEPHALITIS

• Reservoir birds
• Vector mosquito
• Sentinels
• horse,quail, turkey
• Under 15yrs, over 50yrs at higher risk
• CFR 35
• 5 cases/year av.
• horses and humans dead end hosts

CDC
togavirus
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EASTERN EQUINE ENCEPHALITIS
CDC
togavirus
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WESTERN EQUINE ENCEPALITIS

• Reservoir birds
• Vector mosquito
• Sentinels
• horse,quail, turkey
• Children at higher risk
• CFR 3-5
• humans and horses dead end hosts

USA last confirmed human case 1999
togavirus
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CALIFORNIA SEROGROUP ENCEPHALITIS(includes La
Crosse virus)

• Recently commoner in eastern US
• Reservoir small mammals
• Vector mosquitos
• Children at higher risk
• Low CFR
• 80 cases/year av.

bunyavirus
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bunyavirus
2000 - 2 cases in SC, Charleston area
La Crosse life cycle
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ARBOVIRUSES FEVER AND HEMORRHAGIC FEVER
FAMILY FLAVIVIRIDAE Dengue Yellow
fever REOVIRIDAE Colorado tick fever
DISTRIBUTION World wide, especially
tropics Africa, S. and C. America North
America
MAIN DISEASES fever, hemorrhagic
fever hemorrhagic fever fever
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COLORADO TICK FEVER- coltivirus

• Vector tick
• Mild disease in man
• Fever, rash, arthralgia
• RMSF important consideration in differential
  diagnosis
• Probably common, rarely reported

Reovirus family
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DENGUE FEVER

• jungle cycle (monkeys-mosquitoes)
• urban cycle (man-mosquitoes)
• rapidly increasing disease in tropics
• approx. 100-200 cases/yr in US due to import
• occasional indigenous transmission
• 50-100 million cases per year worldwide
• 900,000 cases in Central and S. America in 2007

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http//news.bbc.co.uk/2/hi/americas/6422319.stm pa
tients being treated for Dengue fever in a
Paraguayan hospital
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DENGUE FEVER

• Fever (overlaps with viremic phase)
• headache
• retro-orbital pain
• myalgia, arthralgia
• severe joint and muscle pain breakbone fever
• sometimes rash
• may look like flu, measles, rubella
• more rarely encephalitis

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DENGUE HEMORRHAGIC FEVER/DENGUE SHOCK SYNDROME

• hemorrhages
• plasma leakage
• hemoconcentration
• hypotension
• circulatory failure
• shock

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CDC
DHF - petechiae
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Dengue hemorrhagic fever - pleural effusion
CDC
Vaughn DW et al. J Infect Dis 1997 176322-30.
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DENGUE HEMORRHAGIC FEVER

• immunopathological
• 4 serotypes (1, 2, 3, 4)
• increase in areas in which all 4 circulate has
  led to more cases DHF fever in South and Central
  America
• Entomologic, serologic and virologic conditions
  are now such that locally acquired DHF can occur
  in South Texas
• maternal antibody

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DENGUE HEMORRHAGIC FEVER

• Immune enhancement hypothesis
• more mononuclear cells infected
• infected monocytes release vasoactive
  mediators
• increased vascular permeability
• hemorrhagic symptoms

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DENGUE HEMORRHAGIC FEVER

• do not give aspirin, ibuprofen
• because of anticoagulant affects
• (acetaminophen OK)
• children more severe disease
• CFR depends on rapid response
• can be as low as 1

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YELLOW FEVER

• jungle and urban cycles
• hemorrhages
• degeneration liver, kidney, heart
• CFR 50
• Vaccine (live attenuated)
• important to consider in travel to areas with
  yellow fever
• egg grown
• contraindicated in immune suppression

CDC
last yellow fever epidemic in US - 1905
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The end
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WEST NILE VIRUS
flavivirus
http//www.cdc.gov/ncidod/dvbid/westnile/clinician
s/epi.htm
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WEST NILE VIRUS
flavivirus
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WEST NILE VIRUS

• Case fatality ratio
• Higher in elderly
• The 1 fatality in SC in 2005 was over 65 years
  old
• Peaks about Aug-Sept

SC - 2005
flavivirus
http//westnilemaps.usgs.gov/sc_human.html
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(Time Dec 2007)
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- good vector for Dengue
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1999
West Nile virus
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2000
West Nile virus
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2001
West Nile virus
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2002
West Nile virus
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2003
West Nile virus
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2004
West Nile virus
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2005
West Nile virus
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2006
West Nile virus
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