Title: VIRAL ZOONOSES
1VIRAL ZOONOSES
- ZOONOTIC VIRUSES
- TRANSMISSIBLE FROM ANIMALS
- ARTHROPODS
- often via a blood sucking arthropod
- VERTEBRATES
- bites, body fluids, inhalation etc
2VIRAL ZOONOSES
3transmission
- arthropod vectors (blood sucking)
- Many arboviral diseases world wide (hundreds)
4VIGILANCE
5- ARBOVIRUSES
- FEBRILE DISEASES
- ENCEPHALITIS
- HEMORRHAGIC FEVERS
6ARBOVIRUSES
FAMILY
ENVELOPE yes yes no
SYMMETRY icosahedral helical icosahedral
GENOME ssRNA (ve) ssRNA (-ve) segmented dsR
NA, segmented
7Birds Mammals Humans
8- ARTHROPOD
- Habitat
- Diurnal activity
- Preferred host
- Annual activity
- Overwintering ability
- Transovarial transmission
- VERTEBRATE
- Migratory activity
- Persistence of viremia
- Clinical consequences
- Reservoir ?
- Dead end host?
9PREVENTION
- SURVEILLANCE
- VECTOR CONTROL
- REPELLENTS
- CLOTHING
- TIMING OF ACTIVITY (OR CANCELLATION)
- VACCINE
10SYLVATIC (JUNGLE) CYCLE
11URBAN CYCLE
human cycle
note viruses which have a human cycle may also
have a sylvatic/jungle cycle
12OUTBREAKS
- TEND TO BE SUMMER/EARLY FALL
- SPORADIC
- UNPREDICTABLE
13ARBOVIRAL DISEASE
- MANY DIFFERENT ARBOVIRUSES CAUSE DISEASE
- OFTEN SUB-CLINICAL
14ARBOVIRAL DISEASE
- INITIAL VIRAL REPLICATION
- endothelial cells
- macrophages/monocyte lineage
- INTERFERON (RNA VIRUSES)
- headache, fever, myalgia
- VIREMIA
- spread to target tissues, depending on tropism of
virus
15RECOVERY
- INTERFERON
- CELL-MEDIATED IMMUNITY
- ANTIBODY MAY PLAY A ROLE IN PREVENTING SPREAD
DURING VIREMIC PHASE
16DIAGNOSIS
- Immunological techniques
- RT-PCR for viral RNA
17RESISTANCE
18ARBOVIRUSES ENCEPHALITIS
19ARBOVIRUS ENCEPHALITIS
- SPORADIC
- LOW INFECTIONS -gt CLINICAL CASES
- NOT ALL CASES -gt MAJOR DISEASE
- PROBABLY UNDERDIAGNOSED
20WEST NILE VIRUS
- Reservoir birds
- Vector mosquito
- human, horse
- dead end hosts
flavivirus
http//www.cdc.gov/ncidod/dvbid/westnile/cycle.htm
21flavivirus
West Nile virus
22Final 2008 West Nile Virus activity in the United
States
flavivirus
West Nile virus
23WEST 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
24West 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
25WEST 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
26http//www.cdc.gov/ncidod/dvbid/westnile/resources
/wnv_transplant20brochure6_12_07.pdf
27WEST NILE VIRUS
- transmission
- Mosquito (vast majority of cases)
- Blood transfusion (blood supply is now screened)
- Organ donation
flavivirus
28flavivirus
Reported Human WNV Disease Cases, US 1999
62 2000 21
2001 66 2002
4156 2003 9862
2004 2539 2005
3000 2006 4269 2007
3630 2008 1338 2009 515 (as of
10-20-09)
2008 Case Fatality Rate 44/1356 3.2
29ST. 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
30EASTERN 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
31EASTERN EQUINE ENCEPHALITIS
CDC
togavirus
32WESTERN 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
33CALIFORNIA 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
34bunyavirus
2000 - 2 cases in SC, Charleston area
La Crosse life cycle
35ARBOVIRUSES 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
36COLORADO 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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38DENGUE 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
39http//news.bbc.co.uk/2/hi/americas/6422319.stm pa
tients being treated for Dengue fever in a
Paraguayan hospital
40DENGUE 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
41DENGUE HEMORRHAGIC FEVER/DENGUE SHOCK SYNDROME
- hemorrhages
- plasma leakage
- hemoconcentration
- hypotension
- circulatory failure
- shock
42CDC
DHF - petechiae
43Dengue hemorrhagic fever - pleural effusion
CDC
Vaughn DW et al. J Infect Dis 1997 176322-30.
44DENGUE 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
45DENGUE HEMORRHAGIC FEVER
- Immune enhancement hypothesis
- more mononuclear cells infected
- infected monocytes release vasoactive
mediators - increased vascular permeability
- hemorrhagic symptoms
46DENGUE 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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48YELLOW 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
49The end
50(Time Dec 2007)
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52Aedes albopictus is a species of mosquito which
is a good vector for Dengue
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54WEST NILE VIRUS
flavivirus
http//www.cdc.gov/ncidod/dvbid/westnile/clinician
s/epi.htm
55WEST NILE VIRUS
flavivirus
56WEST 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
571999
West Nile virus
582000
West Nile virus
592001
West Nile virus
602002
West Nile virus
612003
West Nile virus
622004
West Nile virus
632005
West Nile virus
642006
West Nile virus
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