Viral haemorrhagic fever Flashcards
VHF - global distribution
Wide distribution
Total reported cases = 1,500,000
-36,000 cases per year
VHF - transmission
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
VHF - at-risk population
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
VHF - proportion of asymptomatic infections
Ebola = 2.6-6.5%
CCHF = 70%
Lassa = 80%
Marbug = 0%
Difficulty of identifying due to non-specific common symptoms and case definition
VHF - steps for outbreak control
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
Ebola - organism
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]
Ebola - virus structure
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
Ebola - cycle of transmission
‘Single pass’ from animal to human
Amplification by person-to-person
Ebola - largest outbreaks
West African 2013-2016:
-28,800 cases
-11,300 deaths
Ebola - epidemiology
> 20 outbreaks since 1976
CFR [variable across species]:
-EBOV = 40-80%
-SUV = 40-55%
-BDBV = 35-40%
-TAFV = 0%
Ebola - early clinical features
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
Ebola - late phases
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
Ebola - common lab findings
Elevated AST and ALT >1000
Low platelets
Elevated CRP
Leucocytosis, lymphopenia
Ebola - management
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]
Ebola - vaccine
rVSV-ZEBOV:
-Live attenuated recombinant vesiculovirus vaccine
-Ebola Zaire virus specific
Ebola - incubation period
2-21 days
Ebola - diagnosis
PCR - most commonly used
ELISA
Rapid antigen test [OraQuick]
Lassa fever - organism
Lassa virus
Single-stranded RNA virus - family arenaviridae
7 lineages
Lassa fever - animal reservoir
Zoonotic infection transmitted from rodent to humans
Mastomys natalensis [multimammate rat]
Lassa fever - transmission
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]
Lassa fever - epidemiology
80% asymptomatic
only 20% of those become symptomatic
CFR 15% among severe presentation
All age groups affected
M=F
Lassa fever - geographical distribution
Endemic in many West African countries
Largest burden in Nigeria and Sierra Leone
Lassa fever - seasonal pattern
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
Lassa fever - contagious period
2-21 days
Lassa fever - initial symptoms
Vague symptoms:
-Fever
-Generalised weakness
-Malaise
-Headache
-Sore throat = common presentation
-Chest pain
-Myalgia
-N+V
-Diarrhoea
-Pain in back and abdomen [serositis]
Lassa fever - severe symptoms
20% severe symptoms
Facial oedema
ARDS
Hepatitis
Renal failure
Seizures, reduced GCS
Bleeding from orifices
Lassa fever - complications
Bleeding from orifices
DIC
Pleural or pericardial effusion
Renal failure
Multi-organ failure
CNS:
-Encephalitis
-Encephalopathy
-Sensorineural hearing loss
Lassa fever - sensorineural hearing loss
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
Lassa fever - lab diagnosis
Cell culture
IFA
Complement fixation tests
ELISA for LASV antigens and IgM antibodies
PCR
Lateral flow assays
Lassa fever - management
Supportive care
Specific antiviral therapy:
-Ribavirin = more effective during early stages
Lassa fever - future therapeutics
Favipiravir
Zidampidine
Stampidine
AG1478
Crimean-Congo haemorrhagic fever [CCHF] - organism
Tick-borne virus [Nairovirus] in family Bunyaviridae
CCHF - transmission
Tick exposure = Ixodid [hard] ticks
-Genus hyalomma
Contact with blood/tissue of infected animals/person
Occupational disease:
-Famers, HCW, slaughtermen, hunters
CCHF - epidemiology
Geographic distribution - Africa, Central and South Asia
Overall mortality = 20-30%
CCHF - incubation period
IP 1-14 days
Shorter IP with tick transmission
CCHF - clinical manifestations
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
CCHF - differential diagnosis
-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
CCHF - diagnosis
PCR - negative by day 13, highest in 1st week
Serology = IgM and IgG [detectable from day 4]
CCHF - management
Early recognition and infection control
Manage high risk exposures
Contact monitoring
Supportive care
Ribavirin
