Class 10- Hemmoragic Fever Flashcards
1
Q
Why are Ebola and Marburg Viruses of concern and what do they do to the body?
A
- Family of filoviridiae
- Major concern because of high infectivity and mortality rates
- Remember the difference between infectivity and contagiousness?
- Virus disruption of coagulation
- As disease progresses- bleeding becomes progressively worse
- Profuse bleeding from eyes, nose, and eventually vomiting blood due to loss of organ integrity.
- When hiccups occur in the Ebola – Zaire strain, it’s a predictor of death
- As disease progresses- bleeding becomes progressively worse
2
Q
Ebola and Hiccups
A
Hiccups mean the person is almost certain to die (more deadly strain of ebola) and is also how doctors realized the latest outbreak was ebola rather than cholera, malaria or a different hemmorgaic fever
3
Q
Ebola and Marburg reservoir
A
- While early outbreaks of Ebola and Marburg were associated with monkeys they are unlikely to serve as the primary reservoir
- Viruses cause high mortality in primates, and devastatingly high rates in gorillas (has driven them closer to the brink of extinction)
- More than 5,000 gorillas have died from Ebola this past decade
- Once Ebola gets into the human population, human to human transmission occurs.
- It is thought the natural reservoir is several species of fruit bat
- Viruses cause high mortality in primates, and devastatingly high rates in gorillas (has driven them closer to the brink of extinction)
4
Q
Ebola and Marburg Pathogenesis
A
- Virus enters through mucous membranes, breaks in the skin, or parenterally
- Infects many cell types
- Migrates to regional lymph nodes, liver, spleen, and adrenal glands
- Lymphocytes undergo apoptosis resulting in decreased lymphopenia
- Hepatocellular necrosis occurs
- Dysregulation of clotting factors and subsequent coagulopathy
- Hepatocellular necrosis occurs
- Adrenocortical necrosis also can be found
- Associated with hypotension and impaired steroid synthesis
- Lymphocytes undergo apoptosis resulting in decreased lymphopenia
- Pro-inflammatory cytokines cause vascular leak and impairment of clotting ultimately resulting in multi-organ failure and shock
5
Q
Ebola and Marburg virus Clinical Presentation
A
- Reservoir- primarily bats and non-human primates
- Route – index case comes into contact with infected animal blood
- Person to person via infected blood, excretions, organs, or semen
- Handling the bodies of infected deceased
- Most infective towards end stages of disease
- Incubation 2-21 days for both
- Symptoms – fever, myalgia, and headache (acute stages)
- As disease progresses multi-organ failure, terminal shock, and CNS damage
- Symptoms so severe most individuals do not remember being sick as there are few lucid moments
- Communicability- as long as fluids contain the virus
- Corpses can be contagious up to 7 days or longer.
6
Q
Ebola and Marburg treatment
A
- Treat in isolation units, “Haz-Mat” personal protective equipment (PPE):
- Provide supportive measures:
- Hydration, nutrition, fever reduction, electrolytes.
- Rule out / treat other infections (malaria, bacteria)
- Pain & bleeding control
- Up to 90% patient die without supportive therapy.
- Improves to 40% with early diagnosis and good supportive care.
- Case fatality rate 70% overall. Better in Western settings.
- Provide supportive measures:
- Convalescent serum and experimental medications have been tried
- No proven vaccine or specific therapy
7
Q
Why was this Ebola outbreak so difficult to control?
A
- Epicenter is border of three fragile countries.
- Warfare to 2003, dictatorships, extreme poverty
- Weak local systems. 1-2 MDs per 100,000 population
- West Africa’s interconnected populations.
- Ebola is new. Cases detected late.
- Deaths/day, affected countries: Ebola-85, Malaria-500
- Devastating toll on health care workers:
- 423 cases, 239 deaths.
- Global response too slow and limited.
- One private charity (MSF) has treated 2/3 of cases.
- WHO’s operational capacity had been gutted. Relies on national systems.
- Community resistance: Cultural beliefs. Mistrust and fear.
- Collateral damage compounds the crisis
- Closure of hospitals, travel bans, reduction of farming and business.
8
Q
Lassa Fever Clinical Presentation
A
- Reservoir – multimammate rat (shed virus in urine and feces)
- Route – primarily exposure to rat urine and feces, person-to-person transmission is known to occur in both community and health-care settings
- Incubation – 6 to 21 days
- Symptoms – similar presentation as Ebola, lasts 1-4 weeks (death usually occurs by day 14 of clinical symptoms)
- Extremely difficult to tell apart
- Overall case-fatality rate is 1% (80% of infected are asymptomatic)
- Those with symptoms (case fatality rate is 15%)
- Communicability – unknown
9
Q
Prevalence of Viral Hemorrhagic Fevers in Africa 2014
A
- Estimated 100,000 to 300,000 cases per year in Africa of which 5,000 die.
- Estimates are crude due to lack of surveillance
- Person to person transmission primarily occurs in health care settings.
- Can be prevented with standard personal protective equipment (PPE)
10
Q
Bolivian Hemorrhagic Fever (BHF) Clinical Profile
A
- Reservoir - Calomys callosus mouse
- Route – aerosol transmission of dust particles from infected rodents urine and feces
- Incubation – 4 to 21 days
- Sypmtoms – fever, myalgia, bleeding gums and cavities, headache, arthralgia, petechial hemorrhages.
- Can further develop into shock, hematuria, neurological damage, seizures, and comas.
- Fatality rate is 22%.
- Communicability – unknown (person to person is rare and has only occurred in hospital settings)
11
Q
BHF- aka Machupo virus evolution
A
- Eastern Bolivia was converted from Cattle to subsistence agriculture
- Ecological change provided a suitable environment for expansion of mouse population (Calomys callosus)
- Mouse invaded homes resulting in spread of disease
- Epidemic is now under control
- Due in part to the greater pathogenicity of the virus in carrier mouse and more limited contact with reservoir host
12
Q
Argentinian Hemorrhagic Fever (AHF) Clincial Presentation
A
- Causative Agent- Junin Virus
- Reservoir – Maize mouse (Calomys musculinus)
- Route – ingestion and inhalation of infected particles contaminated by rat feces and urine.
- 80 % of those infected are males between the ages of 15-60
- Men are more likely to work in agricultural fields where the maize mouse lives
- 80 % of those infected are males between the ages of 15-60
- Incubation – 10 to 12 days
- Symptoms – fever, headaches, followed by vascular, renal, hematological, and neurological alterations (Stage lasts about 3 weeks)
- If untreated case fatality reaches 15-30%
- Vaccine created in 1985 (95.5% effective)
13
Q
Junin virus
A
- Causes Argentinian Hemorrhagic Fever
- Rodent reservoir commonly found on Maize farms.
- Occupational exposure
- Maize mouse is not significantly impacted by virus, therefore can continue to spread disease.
- Although there is an effective vaccine, AHF continues to occur in unvaccinated populations
- Multiple Arenaviruses were being investigated as potential biological weapons in the US before program was shut down
14
Q
Bunyaviridae
A
- The Bunyaviridae are a very large family of single-strand, enveloped RNA viruses (more than 300 viruses).
- Can cause diseases including hantavirus, rift valley fever, and CCHF
- Reservoir
- Arthropods (e.g. mosquitoes, ticks, sand flies) and rodents
- Several viruses of the Bunyaviridaevirus family can produce mild to severe disease in human, in animals, and sometimes in both.
15
Q
Crimean-Congo Hemorrhagic Fever (CCHF)
A
- Caused by a tick-borne Nairovirus
- First discovered in Crimea, in 1944 and then recognized in the Congo in 1969
- Hence the name
- Transmitted by Ixodid Ticks (Hyalomma genus)
