Viral hem. Fevers

Description:	4th Semester - Micro - Viral Hemorrhagic Fevers
Category:	USMLE
Created by:	null on 2009-05-23

Question	Answer
What is a common characteristic of all viruses that cause hemorrhagic fever?	They are all enveloped RNA viruses.
Describe the structure of flaviviruses	Small, single stranded, postive sense enveloped RNA viruses
Flaviviruses are responsible for what disesaes primarily	Yellow fever and dengue
Yellow fever and dengue are caused by what virus?	Flavivirus
Approx size of flavivirus?	50nm in diameter
What type of mosquito transmits jungle yellow fever to humans	Aedes spp. mosquito
What type of mosquito transmits urban yellow fever to human?	A. aegypti
What is the incubation period of yellow fever?	3 to 6 days
What is the duration of yellow fever?	6-10 days.
What is faget's sign?	The unusual combination of fever and bradycardia. Seen in yellow fever, among other dz's
What are the lab findings of yellow fever?	Leukopenia with relative neutropenia
Clinical presentation of yellow fever in viremic stage	high fever, malaise, chills, ha. myalgia, CONGESTION OF CONJUNCTIVA AND REDDENING OF THE EDGES OF TONGUE
Clinical presentation of yellow fever in late stage?	EPIGASTRIC PAIN AND JAUNDICE, rena dysfunction / oliguria, Increase AST and ALT levels. Global reduction in clotting factors / prolonged PT and bleeding time.
How is yellow fever diagnosed?	Often clinical and epidemiologic. Otherwise, Mostly ELISA.
ddx of yellow fever?	Viral hepatitis, leptospirosis, dengue, etc
what liver cells are first infected?	Kupffer cells.
Can people get yellow fever twice?	No. Being infected once provides life long immunity in the form of neutralizing ABs
What are the two types of dengue?	Classical dengue fever and Dengue hemorrhagic fever / dengue shock syndrome ( mostly in children)
Lab findings of classical dengue?	Leukopenia with absolute neutropenia and elevated AST/ALT
Clinical presentation of dengue?	Abrupt onset of high fever, arthralgia / deep bone pain, CONGESTION OF CONJUNCTIVA, puffy eyelids and RELATIVE BRADYCARDIA, May complain of a metallic taste sensation and epitaxis
Lab findings of dengue hemorrhagic fever.	Same as classical dengue but with elevated hct and throbocytopenia
Likely cause of leukopenia in dengue fever?	BM suppression.
Can you get dengue fever more than once?	Yes. Although long last immunity is achieved through neutralizing antibodies. 2nd infxon is possible from a virus of heterologous sertotype, in which case it is usually the more severe form.
describe structure of FILOviruses.	filamentous, pleomorphic, (-) SSRNA viruses.
What are the two main species of filovirus?	Ebola and Marburg
What is the incubation period of filoviruses?	4 days to 6 weeks
What are the lab findings of filovirus infection (marburg or ebola)	lymphopenia, netropenia, marked thrombocytopenia, elevated AST and ALT with elvated CREATININE AND BUN
Filoviruses infect what cell type?	Mononuclear phagocytes.
rift valley fever is caused by what virus?	phlebovirus
Phlebovirus causes....	rift valley fever
Bunyaviradar consists of what viruses	Bunyavirus, phlebovirus, nairovirus, and hantavirus
Describe structure and size of phleboviirus	segmented (3) (-) SSRNA, enveloped. ~100nm in diameter
Aedes mcintoshi is responsible for transmitting what virus?	phlebovirus. Rift valley fever.
Possible complication of rift valley fever?	Usually benign self limiting disease resolving in 2-5 days. Possible cx include encephalitis, retinitis, and unveitis, likely immune mediated.
Crimean-congo-hemorrhagic fever is caused by what virus	Nairovirus
What is the structure of nairovirus	enveloped, segmented (3) (-)SSRNA (same structure and size [100nm] as phlebovirus)
How is nairo virus transmitted?	Hyalomma ticks. (causes Crimean-congo-hemorrhagic fever)
What virus / dz combo features vomitting, hepatomegally, and neurologic manifestation of somnolence.	Crimean-congo-hemorrhagic fever
Describe structure of hantavirus	same as phlebovirus and nairovirus. (100nm in diameter, segmented (3) (-)SSRNA
How is hantavirus transmitted	rodent urine and feces
Unique clinical manifestations of hemmorhagic fever with renal symptoms.	Febrile stage : Hematuria and proteinurea with conunctival hemorrhage. Hypotension and shock in the hypotensive phase, then progressing to oligouric stage
lassa fever is a finding of what viral infxon	arenavirus
describe arenavirus structure	60-300nm, (-) ssrna
Possible complications if arenavirus infxon	hearing impairments and bacterial superinfection
What is the treatment for lassa fever	Ribavirin
Ribavirin can be used to tx what viral hemorrhagic disease	lassa fever (arenovirus)
What are the main targets for most hemorrhagic fevers causing viruses	Dendritic cells and macrophages
**What cytokine is commonly implicated in hemorrhagic fever?**	TNA-a --> increased endothelial permeability
Innate viral immunity is mediated via,...? cellular immunity?	Innate = INF-alpha, Cellular immunity = CTLs mostly, Humoral = neutralizing antibodies
How do neutralizing antibodies mediate response against viruses that cause hemorrhagic fever?	They mediat oxidation of the viral envelope by compliment
A person with a hemorrhagic fever who recently traveled to Asia is most likely infected with hat virus?	DENV-1,2,3 or 4 (dengue)
A person with a hemorrhagic fever who recently traveled to Arica or South America is most likely infected with what virus?	Yellow Fever Virus (flaviviridae)