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LSHTM > Viral haemorrhagic fever > Flashcards

Viral haemorrhagic fever Flashcards

1
Q

VHF - global distribution

A

Wide distribution

Total reported cases = 1,500,000
-36,000 cases per year

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2
Q

VHF - transmission

A

Initial trigger almost always zoonotic:
-Spill-over to humans
-Unpredictable combination of factors = shedding patterns, land use change, social/economic conditions
-‘Human reservoirs’ - viable virus persists in survivors

Person-to-person:
-Direct contact with contaminated body fluids or objects through broken skin or mucous membranes

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3
Q

VHF - at-risk population

A

People with contact with infected animals, rodents, animal excreta:
-Livestock owners, farmers, forest workers
-Households with infected rodents present

Household members and close contacts:
-Caring activities, symptomatic family members remaining in household
-Sexual partners

Nosocomial exposure:
-HCW, other patients

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4
Q

VHF - proportion of asymptomatic infections

A

Ebola = 2.6-6.5%
CCHF = 70%
Lassa = 80%
Marbug = 0%

Difficulty of identifying due to non-specific common symptoms and case definition

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5
Q

VHF - steps for outbreak control

A

Active case detection
Earlier and more rapid isolation and care
Triage and suspect managemenet
Faster, more frequent testing
IPC - healthcare, household and community
Contact tracing
Quarantine

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6
Q

Ebola - organism

A

Ebola virus = filoviridiae virus

Species:
-BDBV = Bundibugyo virus
-EBOV = Ebola Zaire virus
-SUDV = Sudan virus
-TAFV = Tai Forest virus

No known human disease = Reston virus [RESTV] and Bombali virus [BOMV]

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7
Q

Ebola - virus structure

A

Negative single strand RNA genome
-19 kilobases
-7 distinct genes = NP and GP targets for PCR diagnosis, treatment and vaccines

Lipid envelope easily destroyed by soap, chlorine and UV light

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8
Q

Ebola - cycle of transmission

A

‘Single pass’ from animal to human
Amplification by person-to-person

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9
Q

Ebola - largest outbreaks

A

West African 2013-2016:
-28,800 cases
-11,300 deaths

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10
Q

Ebola - epidemiology

A

> 20 outbreaks since 1976

CFR [variable across species]:
-EBOV = 40-80%
-SUV = 40-55%
-BDBV = 35-40%
-TAFV = 0%

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11
Q

Ebola - early clinical features

A

Early phase:
Day 0-1 = mild fever, headache

Day 2-3 = fever, headache
-Decreased appetite - nausea, onset of diarrhoea [2-3BM/day] - epigastric pain, hiccups

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12
Q

Ebola - late phases

A

GI phase:
Day 4-9 = fever, HA, myalgia
-Increased diarrhoea/vomiting [upwards of 10L/day] - blood diarrhoea/emesis can be seen

Can be renal, encephalopathy and hypoglycaemia phenotypes

Terminal phase:
Day 10-12 = fever and GI symptoms subside
-Confusion and delirium worsen
-Comatose
-Oliguric/anuric

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13
Q

Ebola - common lab findings

A

Elevated AST and ALT >1000
Low platelets
Elevated CRP
Leucocytosis, lymphopenia

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14
Q

Ebola - management

A

Ebola treatment unit:
-Safe burial
-Trace, isolate and treat

Supportive:
-GI losses - IV fluid replacement
-Electrolyte monitoring and replacement
-Septic shock - fluids, prophylactic antibiotics

Experimental therapeutic trials:
-Remdesivir
Ebola Zaire specific:
-MAb114
-ZMAPP [composed of 3 MAbs]
-REGN-EB3 [Regeneron]

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15
Q

Ebola - vaccine

A

rVSV-ZEBOV:
-Live attenuated recombinant vesiculovirus vaccine
-Ebola Zaire virus specific

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16
Q

Ebola - incubation period

A

2-21 days

17
Q

Ebola - diagnosis

A

PCR - most commonly used
ELISA
Rapid antigen test [OraQuick]

18
Q

Lassa fever - organism

A

Lassa virus
Single-stranded RNA virus - family arenaviridae
7 lineages

19
Q

Lassa fever - animal reservoir

A

Zoonotic infection transmitted from rodent to humans

Mastomys natalensis [multimammate rat]

20
Q

Lassa fever - transmission

A

Rodent to human:
-Ingestion of food contaminated with faeces, urine or blood
-Handling, killing and ingesting rodents

Human to human:
-Healthcare settings
-Sexual transmission possible
-Vertical transmission

Most infections are rat-to-human
[unlike Ebola which is mainly human to human]

21
Q

Lassa fever - epidemiology

A

80% asymptomatic
only 20% of those become symptomatic
CFR 15% among severe presentation
All age groups affected
M=F

22
Q

Lassa fever - geographical distribution

A

Endemic in many West African countries

Largest burden in Nigeria and Sierra Leone

23
Q

Lassa fever - seasonal pattern

A

Can occur all year around
Peaks during dry season [December to April]

Although two peaks in both dry and rainy season [June - August] in Sierra Leone

24
Q

Lassa fever - contagious period

A

2-21 days

25
Q

Lassa fever - initial symptoms

A

Vague symptoms:
-Fever
-Generalised weakness
-Malaise
-Headache
-Sore throat = common presentation
-Chest pain
-Myalgia
-N+V
-Diarrhoea
-Pain in back and abdomen [serositis]

26
Q

Lassa fever - severe symptoms

A

20% severe symptoms

Facial oedema
ARDS
Hepatitis
Renal failure
Seizures, reduced GCS
Bleeding from orifices

27
Q

Lassa fever - complications

A

Bleeding from orifices
DIC
Pleural or pericardial effusion
Renal failure
Multi-organ failure
CNS:
-Encephalitis
-Encephalopathy
-Sensorineural hearing loss

28
Q

Lassa fever - sensorineural hearing loss

A

Bilateral or unilateral deafness affecting the 8th cranial nerve

1/3rd infections result in different levels of deafness

No correlation between severity of disease and occurrence

29
Q

Lassa fever - lab diagnosis

A

Cell culture
IFA
Complement fixation tests
ELISA for LASV antigens and IgM antibodies
PCR
Lateral flow assays

30
Q

Lassa fever - management

A

Supportive care
Specific antiviral therapy:
-Ribavirin = more effective during early stages

31
Q

Lassa fever - future therapeutics

A

Favipiravir
Zidampidine
Stampidine
AG1478

32
Q

Crimean-Congo haemorrhagic fever [CCHF] - organism

A

Tick-borne virus [Nairovirus] in family Bunyaviridae

33
Q

CCHF - transmission

A

Tick exposure = Ixodid [hard] ticks
-Genus hyalomma

Contact with blood/tissue of infected animals/person

Occupational disease:
-Famers, HCW, slaughtermen, hunters

34
Q

CCHF - epidemiology

A

Geographic distribution - Africa, Central and South Asia

Overall mortality = 20-30%

35
Q

CCHF - incubation period

A

IP 1-14 days

Shorter IP with tick transmission

36
Q

CCHF - clinical manifestations

A

Acute fever, myalgia, headache

Bleeding from day 3-5

Progressive multisystem involvement [end of 1st week] in 5-30%:
-Thrombocytopenia
-Leucopenia
-Renal failure
-Elevated AST/ALT

37
Q

CCHF - differential diagnosis

A

-Tick-bite fever [Rickettsia africae] = associated with petechial rash and eschar, treatment doxycycline or ciprofloxacin

-Bacterial septicaemia
-Leptospirosis, Q fever, plague
-Malaria, trypanosomiasis
-Viral hepatitis

38
Q

CCHF - diagnosis

A

PCR - negative by day 13, highest in 1st week
Serology = IgM and IgG [detectable from day 4]

39
Q

CCHF - management

A

Early recognition and infection control
Manage high risk exposures
Contact monitoring
Supportive care
Ribavirin

LSHTM (47 decks)

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