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111 Cards in this Set
- Front
- Back
Define vector
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VECTOR: Organism that carries a disease-producing microorganism from one host to another
May be within or on the surface of its body |
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Define ZOONOSIS
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ZOONOSIS: Infection transmitted between humans and animals
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Define ARTHROPOD
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ARTHROPOD: Invertebrate with jointed appendages and chitinous exoskeleton
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Define ARTHROPOD-BORNE VIRUS
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ARTHROPOD-BORNE VIRUS: Arbovirus
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Define NATURAL HOST
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NATURAL HOST: Provides reservoir for an infectious agent in the environment.
Usually not affected |
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Define AMPLIFIER HOST
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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 |
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Define DEAD-END HOST:
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DEAD-END HOST: No further transmission after infection
- incidental host, usually bad disease |
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Define horizontal transmission
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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. |
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Define vertical transmission
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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. |
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define sylvanic cycle
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sylvan; pertaining to, located in, or living in the woods
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vertical transmission of arboviruses - example
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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) |
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Si/Sx of Viral Encephalitis
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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 |
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Si/Sx of Viral Hemorrhagic Fever
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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 |
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Si/Sx of Viral Hemorrhagic Fever (lates stages)
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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 |
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What are the 2 groups of Togaviridae?
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Alpha viruses: Mosquito-borne, Cause encephalitis
Rubivirus: Rubella Virus |
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Name the viruses of togaviridae
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(Alphaviruses)
Sindbis Virus Eastern Equine Encephalitis Virus Western Equine Encephalitis Virus Venezuelan Equine Encephalitis Virus Ross River Virus O’nyong’nyong Virus Chikungunya Virus |
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The must knows of chikungunya
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Must remember: children, arthralgias, mosquitoes, rash
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Another name for chikungunya
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Makonde for “that which bends up”
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where is chikungunya endemic?
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Endemic in most of sub-Saharan Africa, India, SE Asia, and the Philippines
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How is chikungunya maintained?
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Rural and Urban maintenance
Sylvatic: non-human primates and sylvatic Aedes Urban: humans and Aedes aegypti or Aedes albopictus |
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What disease prevelance map is this?
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Cases of chikungunya fever (between 1952-2006)
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Describe aedes aegypti
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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 |
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What is the incubation period of Chikungunya
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Incubation period typically 3-21 days, depending upon the specific virus
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Si/Sx of Chikungunya
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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 |
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Epi of Chikungunya
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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 |
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Summarize Chikungunya
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Widespread in tropics
Mosquito transmission – Aedes spp. Widespread outbreaks occur Fever – Arthiritis – Rash Long-term poly-arthralgias common Death uncommon |
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What type of illnesses do you get from Flavivridae
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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 |
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What are the must knows of West Nile virus
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mosquito transmission
birds are amplifer hosts horses are significantly affected |
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What prevalence map am I?
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WNV 2003
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who are the incidental hosts of wnv?
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humans and horses
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transmission of WNV
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Mosquito vector:
Culex species Cx. quinquefasciatus Cx. tarsalis Cx. pipiens Human to Human: Blood transfusions Organ transplantation Vertical Breast feeding |
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incubation of wnv
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3-14 days
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epi of wnv
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Most infections are asymptomatic
Children are more likely to be asymptomatic or have only mild febrile illness Severity of disease increases with age |
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Si/Sx of wnv
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Sudden onset of fever
Headache Myalgia Prolonged fatigue Gastrointestinal symptoms Generalized lymphadenopathy Up to half, present with generalized roseolar or maculopapular rash |
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Epi of West Nile MeningoEncephalitis
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Approximately 1%
Overall fatality/case ratio- 4-14% Higher ratios in elderly |
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Accompanying abnormalities of West Nile MeningoEncephalitis
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Accompanying abnormalities:
Depressed DTR’s Diffuse muscle weakness Flaccid paralysis Respiratory weakness |
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West Nile PATHOGENESIS
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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 |
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West Nile Summary
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Vector: Culex spp mosquitoes
Birds are amplifier hosts (sentinals) Humans and horses are incidental hosts Encephalitis with flaccid paralysis Increased risk in elderly |
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3 things to remember with Japanese Encephalitis
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mosquitos
rice patties pigs |
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JE Epidemiology
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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) |
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Japanese Encephalitis - how many are symptomatic and in who?
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Only 1-5% cases symptomatic
Up to 90% reported cases in children |
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Si/Sx of JE
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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 |
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what are the JE vaccines?
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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 |
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JE Summary
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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 |
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Compare classic vs old world vs new world yellow fever
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“Classic” hemorrhagic fever known since 1648
“Old World” virus and vector imported to the “New World” via slave trade |
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Where were the 18th-early 20th century epidemics of YF in the Americas
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Philadelphia, 1793, 10% of population killed
New Orleans, 1905: 3,500 cases with 452 deaths |
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What's special about the early 1900s with yellow fever?
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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 |
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what disease distribution am I?
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Yellow Fever 2007
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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 |
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Yellow Fever Epidemiology
- where is it NOT seen? |
YF never seen in Asia: Vector competence of Asian Aedes? Cross-protection from other flaviviruses?
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what amplified YF transmission?
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deforestation
- monkeys play a big role in YF now humans in urban areas |
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Yellow Fever Transmission: Monkeys - describe
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Monkey:
African monkeys usually asymptomatic, but may see die-offs in Americas May have cyclic appearance of YF due to depletion of vertebrate hosts |
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Yellow Fever Transmission: Mosquitoes - describe
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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 |
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Yellow Fever Transmission: Man- describe
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Man
No human-human transmission |
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YELLOW FEVER: incubation
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Intrinsic incubation period: 3-6 days
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YELLOW FEVER: infection case ratio
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Infection-case ratio: as high as 20:1
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YELLOW FEVER: CLINICAL
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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% |
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What are the CLASSIC PERIODS OF
YELLOW FEVER |
Period of infection
Peroid of remission Period of intoxication Recovery |
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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 |
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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 |
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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 |
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17D Yellow Fever Vaccine - describe vaccine
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Live attenuated vaccine
Single dose provides immunity in 95% Boosters recommended every 10 years Required for entry to many countries |
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17D Yellow Fever Vaccine - describe risks and contraindications and cautions
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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 |
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Bunyaviridae - name the three virus groups
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Hantavirus
Phlebovirus: Rift Valley Fever Virus Nairovirus: Crimean-Congo Hemorrhagic Fever |
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Bunyaviridae - name the syndromes
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Hemorrhagic Fever with Renal Syndrome
Hantaan Seoul Puumala Hantavirus Pulmonary Syndrome Sin Nombre Andes Monongahela Bayou |
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Bunyaviridae - Rift valley fever virus - distribution
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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) |
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Bunyaviridae - Rift valley fever virus - what vector
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Mosquito-borne
Aedes spp |
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Bunyaviridae - Rift valley fever virus - describe transmission
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Vertical transmission during dry periods
Heavy rains periodically initiate epizootics |
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Bunyaviridae - Rift valley fever virus - who gets it
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Primarily a disease of domestic livestock
Sheep, goats, cattle, buffalo, and camels Humans are incidental hosts |
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Bunyaviridae - Rift valley fever virus - clinical
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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 |
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Bunyaviridae - Rift valley fever virus - summary
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Mosquito vector
Epidemics after heavy rains and flooding Deaths of young livestock precede human disease Encephalitis and hemorrhagic fever |
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What disease distribution am I?
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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 |
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Crimean-Congo Hemorrhagic Fever - transmission?
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Tick bite (Hyalomma spp.)
May also be acquired from human or animal blood containing virus Slaughterhouse Shearing Nosocomial Other exposures Crushing tick Laboratory |
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What disease distribution am I?
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Crimean-Congo HF
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CCHF: History
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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 |
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CCHF: morbidity mortality
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Mild and asymptomatic cases common
Only 1 in 5 people develop disease Mortality 15-40% |
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CCHF: 4 Stages of Disease
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Incubation: 3-7 days
Pre-Hemorrhagic: 3 days Hemorrhagic: 2-3 days Convalescent (10-20 days after onset) |
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CCHF: 4 Stages of Disease - describe incubation period
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Incubation: 3-7 days
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CCHF: 4 Stages of Disease - describe pre-hemorrhagic period
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Pre-Hemorrhagic: 3 days
Abrupt onset fever, chills, myalgia, severe headache Hyperemia (flushing) of face, neck chest Congested sclera, conjunctiva Occasional nausea, vomiting, diarrhea |
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CCHF: 4 Stages of Disease - describe hemorrhagic period
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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 |
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CCHF: 4 Stages of Disease - describe Convalescent period
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Convalescent (10-20 days after onset)
Labile pulse and shortness of breath Hair loss Xerostomia Polyneuritis, decreased vision and hearing, memory loss |
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CCHF: Treatment
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Supportive measures
Management of hemorrhage and disseminated intravascular coagulation (DIC) Ribavirin? Hyperimmune serum? |
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CCHF Summary
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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 |
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Viral Hemorrhagic Fevers What are the 2 Old world viruses and where are they seen?
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Old World
LCMV - Lymphocytic choriomeningitis - worldwide Lassa - Nigeria - West Africa |
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Lassa Fever Virus - epi
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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 |
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Lassa Fever Virus - txt
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Effective treatment with ribavirin
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Lassa Fever Virus - sequelle
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High rate of hearing loss in survivors
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Lassa Fever Virus - vector
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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 |
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Modes of Transmissionof Lassa Virus
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Rodent-human
Rodent excreta contaminating food Direct contact (consumption or bite) Aerosol Human-human Contact with blood or body fluids Household transmission Nosocomial |
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Clinical Course of Lassa Fever - Stage 1
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STAGE I:
High fever > 39ºC - 41ºC General weakness and malaise Headaches Muscles, articular pain |
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Clinical Course of Lassa Fever - Stage 2
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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 |
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Clinical Course of Lassa Fever - Stage 3
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STAGE 3: - After 7 days
Swollen neck and face (classic for advanced lazza) Confusion/disorientation Mucosal bleeding Internal bleeding |
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Clinical Course of Lassa Fever - Stage 4
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STAGE 4: - After 14 days
Convulsion Bleeding (usually oozing, not frank bleeding, from the gums, vagina, rectum and hemoptysis). Coma Death |
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Clinical Course of Lassa Fever - basics
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Gradual onset
Symptoms similar to those of many other conditions such as typhoid and malaria Incubation Period : 1- 3 weeks |
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Lassa Fever in Pregnancy
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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 |
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Lassa Fever Community Control
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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 |
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Lassa Fever Summary
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Rodent Reservoir/Vector
West Africa Nosocomial Outbreaks Very Sore Throat Facial Edema Proteinuria and Increased AST Ribavirin |
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Filovirus Family
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Marburg virus
Ebola virus |
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History of Ebola and Marburg
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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 |
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Ebola Virus Transmission
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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 |
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Ebola Clinical Disease -incubation
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Incubation period: 5-21 days
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Ebola Clinical Disease - Si/sx
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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 |
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Ebola Clinical Disease - lab finds
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Laboratory findings:
Increased AST/ALT Decreased WBC and PLTs |
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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% (?) |
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Ebola and Marburg Hemorrhagic Fevers - managment strategies
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Primary management strategy is early detection and isolation of infected individuals
Public health overrides individual concern |
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Filovirus Summary
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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 |
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Which VHF viruses are only transmitted directly, vector to humans?
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Lassa, Ebola, Marburg, and Hantaan (hemorrhagic feer with renal syndrome)
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Which VHF viruses are spread nosocomially?
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Lassa, Ebola, Marburg, CCHF
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Which VHF viruses are only transmitted anthropod-borne only?
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Yellow Fever, Dengue
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Which VHF viruses are both directly and transmitted anthropod-borne?
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CCHF and RVF
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what combination of symptoms gives you an 80% PPV it is Lassa fever compared to other febril illnesses?
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combination of fever, exudative pharyngitis, retrosternal pain, and proteinuria
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