Exotic Viruses Flashcards
What are the four exotic viruses?
West Nile virus
Zika virus
Lassa
Dengue
How was West Nile virus uncovered?
People were getting ill at the same time as birds and animals were dying
Vets found quicker than clinicians through PCR that it was West Nile virus which hadn’t really been seen in America before
What did the America variant most closely resemble?
The Israel sequencing
What are the top main clinical features of West Nile virus?
Encephalitis
Fever
Weakness
Meningitis
Where did Zika virus travel?
From Africa, Asia, pacific islands to South America
What was Zika virus first isolated from?
Rhesus monkey in 1947 in zika forest in Uganda
What is Zika virus transmitted by?
Aedes mosquitoes
What may have caused the 2014/2015 zika outbreaks?
World Cup or olympics
What are clinical features of Zika virus?
Incubation period 2-12 days
Only ~20% of adults symptomatic
- fever
- myalgia
- headache
What are complications of Zika virus?
Uveitis
Guillain-Barré syndrome
Meningoencephalitis
Coagulopathy
What group does Zika virus mainly affect?
Pregnant women, children had low birth weights, people were losing babies
Where was Zika virus found in babies?
Placental trophoblasts and foetal endothelial cells
Amniotic fluid
CNS of babies with microcephalic
How does Zika virus travel?
Through sexual contacts , can stain sperm for Zika virus and it on the spermatozoa
What is the guidance for pregnancy and Zika?
If you have been to a zika endemic area, even if the male is asymptomatic, you shouldn’t try to conceive for 6 months after just in case there is an issue
What are viral haemorrhagic fevers?
Ebola
Marburg
Crimean-Congo
Lassa
These have high mortality rate
What was the last case of lassa in this country?
Mother that was unwell, went to Luton, transferred to Cambridge
Person that had travelled was her partner, he had travelled to Africa, past it onto her and she died
What was Lassa fever named after?
After the place where 3 nurses were first found to have it
What is the reservoir for Lassa fever
Mastomys rodents
Can pass onto offspring or through urine and saliva
When are the most human infections of lassa
In dry season, when fields are burnt
What are clinical features of lassa?
Conjunctivitis
Sore throat
Retrosternal chest pain
Vomiting
Back pain
Cough
What can help treat people with lassa?
Ribavirin
What type of virus is dengue?
Flavivirus
What is dengue virus transmitted by?
Mosquitoes mainly aedes aegypti
What percent of the worlds population live in endemic areas for dengue?
40%
What are the phases of dengue virus?
Febrile
Critical
Convalescent
What was the previous clinical classification?
Asymptomatic
Dengue fever
Dengue haemorrhagic fever
Dengue shock syndrome
What is the incubation period for dengue fever?
3-14 days
What are clinical features of dengue fever?
Acute febrile illness
Frontal headache
Myalgia
Nausea and vomiting
Thrombocytopaenia
What are clinical features of dengue haemorrhagic fever?
Haemorrhagic manifestations e.g. bruising, mucosal bleeding
Platelets <100
Evidence of plasma leakage
Often preceded by abdominal pain, vomiting
What are clinical features of dengue shock syndrome?
DHF plus
Narrow pulse pressure
SBP <80mmHg
Sustained abdominal pain
Persistent vomiting
Mortality 12-44%
How many sterotypes of dengue fever are there?
DENV-1, 2, 3, 4
With dengue fever, what can you get antigenic cross reaction with?
Zika virus
What type of immunity does infection with one DENV serotype lead to?
Lifelong immunity to that serotype
Heterologous immunity to other sterotypes for 3 months to 2 years
What does NS1 protein do in dengue?
Pro-inflammatory
Activates complement C3a and C5a
Increases vascular permeability
What was the antibody complication hypothesis?
Non-neutralising in antibody from first infection aids opsonisation via Fc receptors in infection by another serotype
Why does DHS more often occur in patients who have had previous infection?
ADE ( antibody dependent enhancement)
Why is DHS commoner in second infections in Asia and not in S. America?
Viral diversity and ADE
Why is severe dengue disease rare in third and fourth infections?
Improved homologous immunity
Why do children under 6 months not get DHF, and then alter get severe disease?
Waning maternal antibody titres
Also greater baseline vascular permeability in children
Why do Brazilians of African descent get less DHF than non-African descent?
DENV-2 replicates to higher levels in PBMCs from white people than black people
Polymorphisms in OSBPL10 and RXRA
Cross genetic resistance to yellow fever?
What are dengue vaccines?
Dengvaxia - only given to people that have had first infection
Qdenga - given to those that have or have not been infected
Butantan - DV
