Hemorrhagic Fevers Flashcards
Common features from viral hemorrhagic fevers
Affect multiple organs
Damages blood vessels widespread
Affects body’s ability to regulate itself
Main families of viral hemorrhagic fevers
Arenaviridae
- lassa , junin and machupo
Bunyaviridae
- Rift Valley, Bataan and Congo
Filoviridae
- Ebola and Marburg
Flaviviridae
- yellow and dengue
Arenaviridae
Generally rodent transmitted via urine or droppings with humans not being a part of the life cycle normally (zoonotic)
2 segmented single strands of RNA genome that is enveloped
Often seen in west Africa
Lassa virus
Caused by arenaviridae
Acute viral hemorrhagic illness that lasts 2-21 days
Endemic to west Africa
Easily supportive care with rehydration and symptomatic treatment (very low fatality rate)
Bunyaviridae
Large single strand 3-segmented RNA virus that is enveloped
Transmitted via Arthropods and rodents and is a zoonotic virus
Possess:
-the Crimean-Congo hemorrhagic fever (transmitted by ticks and can be transmitted by humans once infected)
- Hantaviruses (Sin Nombre Virus)
- Rift Valley fever (transmitted by mosquitoes and is endemic to sub-Saharan Africa
Filoviridae
Cause severe hemorrhagic fever in humans and nonhuman primates
Single stranded, negative-sense RNA that is enveloped
- have segmented parts called virions that have multiple various shaped filaments (can be branched/long)
- often looks 6 or U shaped*
Produce Marburg and Ebola
Marburg and Ebola
Caused by filoviridae
Severe often fatal illness in humans (produce the highest mortality rates in hemorrhagic fevers)
Transmitted to mammals from fruit bats and then can be spread via human-human transmission
No cure but supportive care improves survival
Marburg mortality rates hover around 50%
Ebola mortality rates can be as high as 90% or as low as 20%
Survivors produce side effects such as tiredness, muscle aches, eye and vision problems and stomach pain
Ebola risk of infection and resistance
Super high chance if in close contact with infected person (3ft-1 meter)
Otherwise low risk
Can remain in areas of the body that are immunologically privileged and body fluids for days
Ebola investigational treatments
Regeneron (REGEN-EB3) and mAb114
Induces overall higher survival rates but not always recommended
- only for confirmed not early stages
Vaccine for Ebola virus
Ervebo
- “host virus” that contains Ebola glycoprotein with very low lethality
- allows for body to produce antibodies/ memory of Ebola specific glycoproteins
Cells that Ebola target
Monocytes and dendritic cells
- as well as lymphocytes indirectly
Leads to cytokine storm, poor stimulation of T helper cells, lymphocyte apoptosis and low antibodies
Flaviviridae
Positive, single-stranded RNA virus that is enveloped
Infects via arthropods
Mosquitoes = yellow, dengue, Zika and west Nile
Ticks = Omsk and tick borne encephalitis
Yellow fever virus
Flaviviridae virus Transmitted via infected mosquitos and found usually in subtropical areas
Symptoms:
- fever aches and pain (acute)
- liver disease w/ bleeding and jaundice (chronic)
- yellow vomiting with the jaundice
Treatment: vaccination
- attenuated vaccine single dose that provides lifelong protection
- if allowed to enter chronic stage, mortality rate is 30-60%*
Primarily Africa and South America
transmission Cycles of yellow fever virus
Jungle (sylvatic)
- mosquitoes -> non human mammals
intermediate (Savannah)
Mosquitoes -> humans in jungle areas
urban
- special mosquito called aedes aegypti
- mosquitoes-> humans in urban areas
Dengue virus
Flavivirideae virus with 4 serotypes
- DENV1-4 (allows for up to 4 different infection chances)
Mosquito borne infection that is increasing in incidence
- severe dengue is the leading cause of death amount children in Asian countries
- one of the only hemorrhagic fevers that humans can be the primary host/ infectious agent*
no treatment just palliative care
-AVOID NSAIDS (causes liver issues)
Dengue virus symptoms
Wide spectrum including severe flu like symptoms, myalgia and nausea
Severe dengue symptoms occur in chronic stage of disease
- severe bleeding, organ failure and plasma leakage are added on top of the severe flu-like symptoms
When to suspect dengue fever
History: person traveled to location known for dengue and now presents with fever/flu-like symptoms
- highly suspect if presents with high fever (40C) and 2 of the following symptoms*
- severe headache
- pain behind the eyes
- muscle and joint pains
- nausea
- vomiting
- swollen glands
- rashes
Critical phase of dengue
Most fatal point in chronic severe dengue
- develops plasma leaking, edema, respiratory distress, hemorrhages and organ failure
- produces 3-7 days after major high fever
- warning signs of severe dengue*
- ab pain
- persistent vomiting
- rapid breathing
- bleeding of gums
- fatigue
- blood in vomit
- restlessness
Dengue virus vaccine
Live attenuated dengue vaccine
- only give to patients that are seropositive for dengue fever ( must have already had dengue fever)
- increases risk of severe dengue in seronegative populations
Requires pre-vaccination screening because of this
What classes of hemorrhagic fever pathogens possess segmented genomes
Bunyaviridae (most segmented genome)
- Rift Valley fever
Arenaviridae
- lasso fever
What classes of hemorrhagic fever pathogens possess non-segmented genomes
Filoviridae
- Ebola and marburg
Most common type of arenaviridae in US?
Lymphocytic choriomengitis virus (LCMV)
Causes meningitis, not as dangerous as lassa fever but lassa is not indigenous to the US
Rift Valley fever virus
Endemic to Africa
Viral zoonotic virus that is transmitted by mosquitoes (and humans once infected)
Treatment is palliative care and prophylaxis actions such as vaccinating animals
- doesn’t usually kill as long as palliative care is given
What is the most lethal hemorrhagic fevers?
Ebola and Marburg
- specifically Ebola
Ebola virus persistence
Survives very well on dry surfaces and can often remain in immunologically privileged areas.
In body fluids can survive up to several days at room temperature
aedes aegypti and aedes albopictus
Two types of mosquitos that are the most common vectors for dengue virus
- aegypti also does yellow fever as well
- albopictus species is more dangerous to the US since their spread is more US friendly and is less temperature sensitive)
Tests to use for dengue fever
Before 7 days after symptom onset
- molecular tests
- dengue virus antigen detection
- serologic tests
- tissue tests
After 7 days from symptom onset
- serologic tests
- tissues only
Serum is used for all tests except tissue
- cerebrospinal fluid is used only for molecular tests*
