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111 Cards in this Set

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Define vector
VECTOR: Organism that carries a disease-producing microorganism from one host to another
May be within or on the surface of its body
Define ZOONOSIS
ZOONOSIS: Infection transmitted between humans and animals
Define ARTHROPOD
ARTHROPOD: Invertebrate with jointed appendages and chitinous exoskeleton
Define ARTHROPOD-BORNE VIRUS
ARTHROPOD-BORNE VIRUS: Arbovirus
Define NATURAL HOST
NATURAL HOST: Provides reservoir for an infectious agent in the environment.
Usually not affected
Define AMPLIFIER HOST
AMPLIFIER HOST: Infection results in increased replication of the agent, augmenting transmission
-may or may not be natural host.
-virus sets up shop and replicates on a large scale
Define DEAD-END HOST:
DEAD-END HOST: No further transmission after infection
- incidental host, usually bad disease
Define horizontal transmission
horizontal transmission the spread of an infectious agent from one individual to another, usually through contact with bodily excretions or fluids, such as sputum or blood, that contain the agent
- the transfer of an infection from person to person; direct transmission of a disease.
Define vertical transmission
vertical transmission transmission from one generation to another. The term is restricted by some to genetic transmission and extended by others to include also transmission of infection from one generation to the next, as by milk or through the placenta.
- the transmission of a disease from mother to child either during pregnancy, childbirth, or by breastfeeding.
define sylvanic cycle
sylvan; pertaining to, located in, or living in the woods
vertical transmission of arboviruses - example
ARTHROPOD FEEDS ON INFECTED VERTEBRATE
-->
ARTHROPOD OVIPOSITS - EGG CONTAINS VIRAL RNA
-->
EGG HATCHES: LARVAL, PUPAL, AND ADULT STAGES
-->
ADULT EMERGES, ALREADY INFECTED AND CAPABLE OF TRANSMISSION

(% TRANSOVARIAL TRANSMISSION VARIES: <<1 - 99)
Si/Sx of Viral Encephalitis
Abrupt onset headache, fever, myalgias, meningeal signs
Progression to confusion, coma, convulsions, death
Cerebral edema
Duration: days to weeks
Sequelae: Deafness, decreased cognitive function, depression
Si/Sx of Viral Hemorrhagic Fever
Initial prodrome lasts a few days: fever, malaise, myalgia leading to prostration

Difficult to distinguish from other febrile diseases, especially in the early phases

Severe headache common

GI symptoms common: anorexia, nausea, vomiting, diarrhea

Abdominal pain may mimic surgical abdomen

Cough, dyspnea, chest pain may be seen
Si/Sx of Viral Hemorrhagic Fever (lates stages)
Late stages: agitation, confusion, tremor to coma and convulsions

Progresses to shock, multi organ-system failure, and death

Hemorrhage in a minority of cases
not usually large in volume

Pathogenesis of severe cases involves a lethal combination of increased CAPILLARY PERMEABILITY, IMPAIRED COAGULATION AND OFTEN IMPAIRED CARDIAC FUNCTION
What are the 2 groups of Togaviridae?
Alpha viruses: Mosquito-borne, Cause encephalitis

Rubivirus: Rubella Virus
Name the viruses of togaviridae
(Alphaviruses)
Sindbis Virus
Eastern Equine Encephalitis Virus
Western Equine Encephalitis Virus
Venezuelan Equine Encephalitis Virus
Ross River Virus
O’nyong’nyong Virus
Chikungunya Virus
The must knows of chikungunya
Must remember: children, arthralgias, mosquitoes, rash
Another name for chikungunya
Makonde for “that which bends up”
where is chikungunya endemic?
Endemic in most of sub-Saharan Africa, India, SE Asia, and the Philippines
How is chikungunya maintained?
Rural and Urban maintenance
Sylvatic: non-human primates and sylvatic Aedes

Urban: humans and Aedes aegypti or Aedes albopictus
What disease prevelance map is this?
Cases of chikungunya fever (between 1952-2006)
Describe aedes aegypti
Lives around human habitation
Lays eggs and produces larvae preferentially in artificial containers (tires, refuse, etc.)
Primarily day-time biters
Nervous feeders
increased interrupted feeding = increased spread
What is the incubation period of Chikungunya
Incubation period typically 3-21 days, depending upon the specific virus
Si/Sx of Chikungunya
Sudden onset of:
Fever
Joint pain, sometimes with swelling
Maculopapular rash occurs 4-8 days after initial symptoms
“Irritating” or “itchy”
May be accompanied by increase in fever

Joint pains may reoccur without fever or rash for many months after initial illness (up to a year)

Fatalities or long-term sequelae are rare

Headache
Lymphadenitis in some forms
Conjunctivitis in some forms
Epi of Chikungunya
Sometimes large urban outbreaks - Typically occur in the rainy season

High potential for introduction in other areas where vectors are present

Massive outbreak in the island nations off the coast of Africa, spreading to India and southeast Asia
100,000s of infections
Spread to Italy
Summarize Chikungunya
Widespread in tropics
Mosquito transmission – Aedes spp.
Widespread outbreaks occur
Fever – Arthiritis – Rash
Long-term poly-arthralgias common
Death uncommon
What type of illnesses do you get from Flavivridae
Hepatitis C
Tick-borne Viruses :Tick-borne encephalitis
Mosquito-borne Viruses:
Dengue Virus
Kyasanur Forest Disease
Murray Valley Encephalitis
St. Louis Encephalitis
Japanese encephalitis virus
West Nile virus
Yellow Fever Virus
What are the must knows of West Nile virus
mosquito transmission
birds are amplifer hosts
horses are significantly affected
What prevalence map am I?
WNV 2003
who are the incidental hosts of wnv?
humans and horses
transmission of WNV
Mosquito vector:
Culex species
Cx. quinquefasciatus
Cx. tarsalis
Cx. pipiens

Human to Human:
Blood transfusions
Organ transplantation
Vertical
Breast feeding
incubation of wnv
3-14 days
epi of wnv
Most infections are asymptomatic

Children are more likely to be asymptomatic or have only mild febrile illness

Severity of disease increases with age
Si/Sx of wnv
Sudden onset of fever
Headache
Myalgia
Prolonged fatigue
Gastrointestinal symptoms
Generalized lymphadenopathy
Up to half, present with generalized roseolar or maculopapular rash
Epi of West Nile MeningoEncephalitis
Approximately 1%

Overall fatality/case ratio- 4-14%
Higher ratios in elderly
Accompanying abnormalities of West Nile MeningoEncephalitis
Accompanying abnormalities:
Depressed DTR’s
Diffuse muscle weakness
Flaccid paralysis
Respiratory weakness
West Nile PATHOGENESIS
Initial viral replication occurs in Langerhans cells after inoculation

Viremia leads to infection of peripheral organs

Dissemination to CNS: hippocampus, cerebellum, brain stem, cerebral cortex, anterior horn cells
West Nile Summary
Vector: Culex spp mosquitoes

Birds are amplifier hosts (sentinals)

Humans and horses are incidental hosts

Encephalitis with flaccid paralysis

Increased risk in elderly
3 things to remember with Japanese Encephalitis
mosquitos
rice patties
pigs
JE Epidemiology
Up to 175,000 cases per year
Leading cause of neurologic disease
Exceeds HSV in endemic areas
Reservoir: birds
Pigs are amplifier hosts
Vector: mosquitoes (Culex tritaeniorhynchus)
Japanese Encephalitis - how many are symptomatic and in who?
Only 1-5% cases symptomatic
Up to 90% reported cases in children
Si/Sx of JE
Acute onset fever, lethargy, headache
Agitated delirium, unsteadiness, abnormal motor movements
Somnolence, seizures, coma
Mortality: 25%
Sequelae:
33%: blindness, seizures, movement d/o
75%: behavioral and psychological abnl
what are the JE vaccines?
Travelers – Ixiaro®
Live-attenuated virus
Indicated for long-term travelers or short-term and staying in rural areas

Inactivated and live-attenuated
Routinely given to children in SE Asia
JE Summary
Endemic to large portions of Asia and Pacific
Pigs are amplifier host
Severe disease in children
Encephalitis with behavioral changes
Symptomatic cases with high mortality and long term sequelae
Compare classic vs old world vs new world yellow fever
“Classic” hemorrhagic fever known since 1648
“Old World” virus and vector imported to the “New World” via slave trade
Where were the 18th-early 20th century epidemics of YF in the Americas
Philadelphia, 1793, 10% of population killed
New Orleans, 1905: 3,500 cases with 452 deaths
What's special about the early 1900s with yellow fever?
Walter Reed works out virus and mosquito relationship. First recognized arbovirus
Gorgas able to control YF in Cuba and Panama through mosquito control, allowing completion of the Panama canal
what disease distribution am I?
Yellow Fever 2007
Yellow Fever Epidemiology
- where is it seen?
Seasonal fluctuations
Africa: transmission begins during rainy season and peaks during dry season
Americas: peak during rainy season
Urban YF: Can extend throughout year
Yellow Fever Epidemiology
- where is it NOT seen?
YF never seen in Asia: Vector competence of Asian Aedes? Cross-protection from other flaviviruses?
what amplified YF transmission?
deforestation
- monkeys play a big role in YF now humans in urban areas
Yellow Fever Transmission: Monkeys - describe
Monkey:
African monkeys usually asymptomatic, but may see die-offs in Americas
May have cyclic appearance of YF due to depletion of vertebrate hosts
Yellow Fever Transmission: Mosquitoes - describe
Mosquito:
Extrinsic incubation period of YF virus: 7-17 days
Vertical (transovarial) transmission allows persistence through dry periods
Savanna (“zone of emergence”) transmission from sylvatic mosquitoes
Yellow Fever Transmission: Man- describe
Man
No human-human transmission
YELLOW FEVER: incubation
Intrinsic incubation period: 3-6 days
YELLOW FEVER: infection case ratio
Infection-case ratio: as high as 20:1
YELLOW FEVER: CLINICAL
Range of presentations: non-specific febrile illness to life-threatening hemorrhagic disease
Liver is the principle target organ: direct viral damage
Severe cases: shock, delirium, hypothermia, coma, and death 7-10 days after onset of illness
Case fatality rate: ~20%, range 3-50%
What are the CLASSIC PERIODS OF
YELLOW FEVER
Period of infection
Peroid of remission
Period of intoxication
Recovery
Describe the period of infection: CLASSIC PERIODS OF
YELLOW FEVER
PERIOD OF INFECTION: 2-3 days.
Patient viremic (infectious).
Sudden onset of fever, chills, malaise, headache, back and muscle pain, anorexia, nausea and dizziness.
Pulse-temperature dissociation
Describe the period of remission: CLASSIC PERIODS OF
YELLOW FEVER
PERIOD OF REMISSION: < 1 day.
Not always present
Patient may continue to improve at this point
Describe the period of intoxiation: CLASSIC PERIODS OF
YELLOW FEVER
Period of intoxication:
Recurrence of earlier symptoms plus
jaundice, epigastric pain, renal dysfunction
Hemorrhage: gastrointestinal tract, mucous membranes, venupuncture sites, vagina
petechiae, purpura
Antibodies appear
17D Yellow Fever Vaccine - describe vaccine
Live attenuated vaccine
Single dose provides immunity in 95%
Boosters recommended every 10 years
Required for entry to many countries
17D Yellow Fever Vaccine - describe risks and contraindications and cautions
Contraindicated in children <4 months and pregnant women

Risks:
YEL-AND (Assocaited Neurtropic disease) & YEL-AVD(Associated Visceral Disease)

Caution with use:
egg allergy
immunocompromised
children 4-9 months of age
Give only if high risk of disease
Bunyaviridae - name the three virus groups
Hantavirus

Phlebovirus: Rift Valley Fever Virus

Nairovirus: Crimean-Congo Hemorrhagic Fever
Bunyaviridae - name the syndromes
Hemorrhagic Fever with Renal Syndrome
Hantaan
Seoul
Puumala

Hantavirus Pulmonary Syndrome
Sin Nombre
Andes
Monongahela
Bayou
Bunyaviridae - Rift valley fever virus - distribution
Sudden outbreaks following heavy rains
Sentinel deaths of young ruminants (especially lambs & calves) abortion in pregnant adults
Human epidemics may occur in association with epizootics
Mosquito bite (and possibly bites from other arthropods)
Direct exposure to diseased animals (farmers, slaughterhouses, contaminated meat)
Bunyaviridae - Rift valley fever virus - what vector
Mosquito-borne
Aedes spp
Bunyaviridae - Rift valley fever virus - describe transmission
Vertical transmission during dry periods

Heavy rains periodically initiate epizootics
Bunyaviridae - Rift valley fever virus - who gets it
Primarily a disease of domestic livestock
Sheep, goats, cattle, buffalo, and camels
Humans are incidental hosts
Bunyaviridae - Rift valley fever virus - clinical
Four syndromes recognized in humans:
Asymptomatic or mild febrile illness (majority)
Ocular disease
Hemorrhagic fever
Encephalitis
Human mortality low (~1%)
Treatment supportive (ribavirin?)
Vaccine approved for animals, but experimental for humans
Bunyaviridae - Rift valley fever virus - summary
Mosquito vector
Epidemics after heavy rains and flooding
Deaths of young livestock precede human disease
Encephalitis and hemorrhagic fever
What disease distribution am I?
RVF: (green) Endemic disease and substantial outbreaks: Gambia, Senegal, Mauritania, Namibia, South Africa, Mozambique, Zimbabwe, Zambia, Kenya, Sudan, Egypt, Madagascar, Saudi Arabia, Yemen

(Blue) Occasional cases, periodic isolation of virus, or serologic evidence: Botswana, Angola, Democratic Republic of the Congo, Congo, Gabon, Cameroon, Nigeria, Central African Republic, Chad, Niger, Burkina Faso, Mali, Guinea, Tanzania, Malawi, Uganda, Ethiopia, Somalia
Crimean-Congo Hemorrhagic Fever - transmission?
Tick bite (Hyalomma spp.)

May also be acquired from human or animal blood containing virus
Slaughterhouse
Shearing
Nosocomial

Other exposures
Crushing tick
Laboratory
What disease distribution am I?
Crimean-Congo HF
CCHF: History
Disease described in Crimea and central Asian republics in 1944-1947

Virus isolated in Congo in 1956 and later shown identical to 1947 Russian isolate
CCHF: morbidity mortality
Mild and asymptomatic cases common
Only 1 in 5 people develop disease

Mortality 15-40%
CCHF: 4 Stages of Disease
Incubation: 3-7 days
Pre-Hemorrhagic: 3 days
Hemorrhagic: 2-3 days
Convalescent (10-20 days after onset)
CCHF: 4 Stages of Disease - describe incubation period
Incubation: 3-7 days
CCHF: 4 Stages of Disease - describe pre-hemorrhagic period
Pre-Hemorrhagic: 3 days
Abrupt onset fever, chills, myalgia, severe headache
Hyperemia (flushing) of face, neck chest
Congested sclera, conjunctiva
Occasional nausea, vomiting, diarrhea
CCHF: 4 Stages of Disease - describe hemorrhagic period
Hemorrhagic: 2-3 days
Petechiae to large hematomas
Bleeding from nose, gums, gi tract, uterus, bladder, lungs
Cerebral hermorrhage
Leukopenia, thrombocytopenia, hemoconcentration, proteinuria, elevated AST
CCHF: 4 Stages of Disease - describe Convalescent period
Convalescent (10-20 days after onset)
Labile pulse and shortness of breath
Hair loss
Xerostomia
Polyneuritis, decreased vision and hearing, memory loss
CCHF: Treatment
Supportive measures

Management of hemorrhage and disseminated intravascular coagulation (DIC)

Ribavirin?

Hyperimmune serum?
CCHF Summary
Tick vector
Africa, Asia, Middle East
Most cases occur during outbreaks
4 stages of disease
Hemorrhagic stage
Convalescent stage with neurologic sx and labile pulse
Viral Hemorrhagic Fevers What are the 2 Old world viruses and where are they seen?
Old World
LCMV - Lymphocytic choriomeningitis - worldwide
Lassa - Nigeria - West Africa
Lassa Fever Virus - epi
First discovered in Nigeria in 1969

Endemic in areas of West Africa
300,000-500,000 infections/year
5,000 deaths/year

Case fatality rate: 20-25% of hospitalized cases
Lassa Fever Virus - txt
Effective treatment with ribavirin
Lassa Fever Virus - sequelle
High rate of hearing loss in survivors
Lassa Fever Virus - vector
Mastomys Species Complex
“Multimammate rat”
Peri-domestic
Inhabits fields and cleared forest
Prolific breeder (~8-12 pups/litter)
Infected at birth and become chronic asymptomatic carriers of Lassa virus
Shed virus in the urine and feces
Modes of Transmission of Lassa Virus
Rodent-human
Rodent excreta contaminating food
Direct contact (consumption or bite)
Aerosol

Human-human
Contact with blood or body fluids
Household transmission
Nosocomial
Clinical Course of Lassa Fever - Stage 1
STAGE I:
High fever > 39ºC - 41ºC
General weakness and malaise
Headaches
Muscles, articular pain
Clinical Course of Lassa Fever - Stage 2
STAGE 2: after 4 – 7 days

Sore throat (with white exudative patches) very common
Persistent headache
Generalize body pain
Abdominal pain
Conjunctivitis (Red eyes)
Nausea and vomiting
Diarrhea
Low blood pressure (systolic BP < 100)
Productive cough
Clinical Course of Lassa Fever - Stage 3
STAGE 3: - After 7 days
Swollen neck and face (classic for advanced lazza)
Confusion/disorientation
Mucosal bleeding
Internal bleeding
Clinical Course of Lassa Fever - Stage 4
STAGE 4: - After 14 days
Convulsion
Bleeding (usually oozing, not frank bleeding, from the gums, vagina, rectum and hemoptysis).
Coma
Death
Clinical Course of Lassa Fever - basics
Gradual onset
Symptoms similar to those of many other conditions such as typhoid and malaria
Incubation Period : 1- 3 weeks
Lassa Fever in Pregnancy
Increased maternal mortality in third trimester (>30%)
Increased fetal and neonatal mortality (>85%)
Increased level of viremia in pregnant women
Placental infection
Evacuation of uterus improves mother’s chance of survival
Lassa Fever Community Control
Most control programs focus on minimizing human-rodent contact

Good “village hygiene”:
Disposal of garbage
Appropriate storage of food-stuffs
Avoid rodents as a food source
Keep cats?
Avoid close contact with household members with compatible febrile illnesses

No Lassa vaccine currently available
Lassa Fever Summary
Rodent Reservoir/Vector
West Africa
Nosocomial Outbreaks
Very Sore Throat
Facial Edema
Proteinuria and Increased AST
Ribavirin
Filovirus Family
Marburg virus

Ebola virus
History of Ebola and Marburg
Marburg outbreak in lab in Germany in 1967

Ebola first discovered in 1976 after nosocomial outbreaks in Zaire and Sudan

Named “Ebola” after a river in Zaire

Largest outbreak ever (425 people) occurred in Uganda in 2000-2001
Ebola Virus Transmission
Primary reservoir likely bats
Direct contact and/or aerosol transmission

Non-human primates
Develop severe disease like humans

Inter-human transmission through direct contact with blood/body secretions

Nosocomial transmission:
Poor infection control practices (needle reuse, lack of gloves, etc.)

Human-to-human transmission in the community - Ritual burial practices
Ebola Clinical Disease -incubation
Incubation period: 5-21 days
Ebola Clinical Disease - Si/sx
Abrupt onset, often severe disease
Fever, chest pain, cough, pharyngitis
Abdominal pain and diarrhea
LAD, conjunctival injection, jaundice, pancreatitis
Photophobia, somnolence, coma
>50% hemorrhagic symptoms
Ebola Clinical Disease - lab finds
Laboratory findings:
Increased AST/ALT
Decreased WBC and PLTs
Ebola and Marburg Hemorrhagic Fevers mortality
- therapy
- vaccine
Mortality high, no specific therapy, no vaccine
Zaire 70-80% mortality
Sudan 50-60%
Bundibugyo 24% (?)
Reston 0% (?)
Ebola and Marburg Hemorrhagic Fevers - managment strategies
Primary management strategy is early detection and isolation of infected individuals
Public health overrides individual concern
Filovirus Summary
Reservoir: bats and pigs (?)
Humans and non-human primates become ill
Mainly occurs in outbreaks
High risk of nosocomial transmission
High mortality
Severe hemorrhage not absolute
Which VHF viruses are only transmitted directly, vector to humans?
Lassa, Ebola, Marburg, and Hantaan (hemorrhagic feer with renal syndrome)
Which VHF viruses are spread nosocomially?
Lassa, Ebola, Marburg, CCHF
Which VHF viruses are only transmitted anthropod-borne only?
Yellow Fever, Dengue
Which VHF viruses are both directly and transmitted anthropod-borne?
CCHF and RVF
what combination of symptoms gives you an 80% PPV it is Lassa fever compared to other febril illnesses?
combination of fever, exudative pharyngitis, retrosternal pain, and proteinuria