Arboviruses causing Haemorrhagic fever Flashcards Preview

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Which class of arboviruses cause Dengue virus and Yellow fever?



What disease do Bunyaviruses cause?

Rift valley fever, crimea congo haemorrhagic fever


How are Dengue virus and yellow fever transmitted?



What type of viruses are Flaviviruses?

RNA viruses


What is VHF and which type of Viruses cause it?

Viral haemorrhagic fever, a group of febrile illnesses caused by RNA viruses.
Infection may lead to a potentially lethal disease syndrome characterised by fever, malaise, vomiting, mucosal and gastrointestinal bleeding, edema and hypotension.


Are flaviviruses and bunyaviruses VHF families?



Describe Dengue fever, including it's vector, geographical areas of infection, and manifestation of disease

-Dengue fever is the most important arbovirus in humans, it infects 50 million per year, with 10% of these cases developing dengue haemorrhagic fever.
-It is found mainly in tropical/subtropical regions and is an important cause of fever in the returned traveller.
-It's principal vector is Aedes aegypti, a mosquito that bites during both the night and the day
-Dengue fever has a 4-7 day incubation period. There is a wide spectrum of disease: asymptomatic, self-limiting (dengue fever), to Dengue haemorrhagic fever (DHF) and Dengue shock syndrome (DSS)
-Classically, dengue fever causes: sudden onset fever, chills, headache, retro-orbtial pain, myalgia (why it's also called break bone fever), nausea, vomiting and diarrhoea.
-Symptoms last 2-7 days


Describe DHF

Particularly affects children in dengue endemic regions and usually occurs with secondary dengue infection when infected with a different viral serotype.
Most cases are uncomplicated with fever, thrombocytopenia, bleeding from mucosal surfaces, skin petechiae and conjunctival haemorrhage


Describe DSS

-Dengue Shock Syndrome
-Characterised by bleeding diathesis and hypovolaemic shock - and emergency condition where severe blood and fluid loss leave the heart unable to pump enough blood to organs
-Early symptoms may be indistinguishable from DHF
-Abatement of fever 2-7 after infection starts is observed, followed by reduced perfusion and early signs of shock. Abdominal pain and heptamegaly is common


What are fatality rates of DHF and DSS in medically underresourced areas?

Up to 50%


How would you diagnose Dengue fever in a Laboratory?

FBC - thrombocytopenia and lymphocytosis are common
PCR plasma - virus may be detectable in early infection


Describe yellow fever

-Aedes aegypti is the principal mosquito vector
-There's a natural life cycle between forest-dwelling monkeys and mosquitos
-3-6 day incubation period
-Disease spectrum varies from undifferentiated febrile illness to haemorrhagic fever with high mortality (up to 50%)
-Virus initially replicates in the local lymph nodes, then infects the liver, lungs, kidneys, bone marrow, adrenals and spleen
-Typically presents with abrupt onset fever, chills, and headache. Most patients recover after 3-4 days
-Typical symptoms include fever, bradycardia, jaunice and haemorrhagic manifestations including petechial haemorrhages, epistaxis, bleeding gums and GI haemorrhage.
-50% of patients with yellow fever will develop fatal disease


How do you diagnose yellow fever in a laboratory?

Mainly via serology - detect specific IgM and and increase in titre of IgG/totalAb
PCR may be useful early on


Is there a vaccine for Dengue fever or yellow fever?

There is one available for yellow fever, not Dengue


What are the Flaviviruses?

Dengue Fever
Yellow fever
Japanese encephalitis
Murray Valley encephalitis


What are the bunyaviruses?

Rift Valley Fever
Crimean Congo haemorrhagic fever


What are the alpha viruses, and what symptom of arboviruses are they characterised by?

1. Chikungunya fever
2. Ross River virus
3 Barmah Forest Virus

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