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Sunday, February 1, 2009

Flaviviridae

Three types of virus that is under the Flaviviridae:
§ Flavivirus
§ Pestivirus ( Yellow Fever, Dengue, West Nile )
§ Hepacivirus ( Hepatitis C )

The focus of the contents is on the causes, control, prevention, diseases on (Yellow Fever, Dengue, and West Nile).



Dengue
· The most arbovirus presently
· Non-fatal dengue fever (DF)
· Usually fatal dengue haemorrhagic fever (DHF) / Dengue shock syndrome (DSS)
· Dengue has 4 distinct serotypes based on neutralisation test. DEN-1 ,DEN-2,DEN-3,DEN-4
· DEN-2 shows the greatest antigenic and genotypic distance from the others.
· Mainly is DEN-2 that cause 60% of people reported having DHF.

Dengue Infection Life Cycle




Differences between Dengue Fever and Dengue Haemorrhagic Fever / Dengue Shock Syndrome
Dengue Fever




There is different grading of DHF:





Pathogenesis of DHF / DSS
Ø Not well understood despite intensive study – 2 theories
Ø Virulent strain theory
· Some strains more virulent than others
· Molecular studies show variations in sequences amongst different strains within serotypes
Ø Antibody enhancement
· Main theory for DHF / DSS
· Main cell target of DEN: monocytes / macrophages
· Most cases of DHF / DSS had prior infection or infants below 1 year had maternal Ab
· Monkey experiment showed similar enhancement





Possible cause of DHF / DSS
- Immune system overreacting
- Sever acute respiratory syndrome

Transmission is by Dengue Mosquito

Control of Dengue
1. Insecticide
2. Mosquito screen
3. Remove stagnant water

Patient with DHF / DSS




Videos:



Yellow Fever

· It is a tropical disease in Latin America and Africa
· Incubation period : 3 – 6 days
· Infectious , headache, malaise, nausea, lassitude , muscle ache (3days)
· Flushing of head & neck, conjunctival injection, strawberry tongue



Severe Yellow Fever
§ Remission after acute yellow fever
§ Haemorrhagic, hepatic and renal disease
§ Fever, vomiting, abdominal pain, dehydration, prostration
§ Haemorrhagic / coffee-ground diathesis (black vomit)
§ Bleeding from puncture sites of injections and drip needles
§ Jaundice
§ Massive haematemesis
§ Renal failure, hypotension, shock
§ Virus absent from blood, but antibody titre high – implying autoimmunity may play major role
§ Survivors suffered extended chronic jaundice before full recovery; hepatic and renal failure may persist



Controls
There is only a way: Attenuated vaccine



Videos:



West Nile Virus
· Originated in Uganda
· Discovered in 1937
· Common in Africa, west Asia, Europe, Middle East
· Mainly mild to no symptoms
· Fever, headache, body rashes, skin rash , swollen lymph glands
· Severe symptoms
§ Crossing blood brain barrier
§ Encephalitis
§ Meningitis
· Mainly in persons above 50 years

West Nile Virus Transmission Cycle



Control
There is no control towards West Nile virus.


Video:




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