viral bio weapons Flashcards
viral hemorrhagic fevers (in general)
severe multisystem syndromes
the overall vascular system is damaged, and the body’s ability to regulate itself is impaired.
often accompanied by hemorrhage
what kind of virus is Lassa fever?
arenavirus
what kind of virus is CCHF (congo crimean hemorrhagic fever)
bunyavirus
what kind of virus is ebola?
filovirus
what kind of virus is yellow fever?
flavivirus
what kind of virus is marburg?
filovirus
what kind of virus is hantaviruses (HFRS and HPS)?
bunyaviruses
properties of VHF agents (viral hemorrhagic fever agents)
all are enveloped RNA viruses dependent on animal or insect host
patient history includes: foreign travel, rural env, animal exposure
no cure or established treatment
Leptospirosis
bacterial VHF vasculitis + hemrrhagic rash
d/t leptospira
with enlargement of spleen, jaundice and nephritis
waterhouse-friderichsen syndrome
bilateral, hemorrhage into the adrenal glands caused by fulminant meningococcemia.
characterized by: (1) overwhelming bacterial infection (2) Rapid hypotension leading to shock (3) DIC (disseminated intravascular coagulation) with widespread purpura
HUS
occurs after bloody diarrhea caused by E. coli O157:H7, a strain that expresses verotoxin (also called Shiga toxin).
hemolysis –> dark urine “black water fever” is d/t…
falciparum malaria
usually treatment for a VHF is based on
supportive care
can maybe treat arenaviruses and bunyaviruses (CCHF, Hantaviruses, RVF) with
ribavirin
what VHFs have vaccines?
yellow fever and argentine hemorrhagic fever
how lethal is ebola virus?
up to 90%
ebola and marburg
filoviruses
long, sometimes branched filaments, shorter filaments shaped like a “6”, a “U”, or circles.
they are enveloped ssRNA - sense
likely reservoir of ebola?
bats in africa
which ebola subtype is not pathogenic for humans?
reston type; the other four are!
transmission/diagnosis of ebola
Infections are acute = no carrier state.
Transmitted by direct contact with blood and secretions of an infected person, and through contaminated needles etc.
Diagnosis: difficult in early stages because of non-specific early symptoms (e.g. red eyes and a skin rash).
CCHF
transmission and vector
crimean congo hemorrhagic fever
transmitted by hyalomma tick
or contact with animal pre/post slaughter
-
virus that causes CCHF
a bunyavirus
genome is circular, ambisense RNA (+ and -) in three parts - Small (S), Middle (M) and Large (L).
Lassa fever and S. american hemorrhagic fevers (LCMV)
arenaviruses
rodent hosts
virions are envelped and have a grainy appearance due to ribosomes
genome has 2 strands of ambisense RNA (some + and some -; S and L)
Lassa fever (arenavirus)
transmission
Contact with rodent (rats) excreta - contaminated food, broken skin, inhalation of tiny particles soiled with rodent urine or saliva (aerosol transmission)
virus is shed in the urine and feces
**can be rodent to human or human to human(body fluids)
Lassa fever
caused by arenavirus Lassa
Rodent reservoir –Mastomys (“multimammate rat)”
signs and symptoms of lassa fever
Occur 1-3 weeks after infection
Fever, retrosternal pain, sore throat, abdominal pain, vomiting, diarrhea, conjunctivitis, facial swelling, and mucosal bleeding. Neurological signs also seen
Most common complication of Lassa fever (1/3 cases) is deafness.
most common complication of lassa fever is
deafness
swollen baby syndrome
lassa fever in infants
Edema, Abd distension, & Bleeding = Poor prognosis
Treatment: supportive care & Ribavirin
A 50-year-old man from Sierra Leone who has been living in the US but went home for a week to visit his family, presents to your clinic with fever, chills and multiple joint pain. He informs you that he spent five days in his rural home village sleeping in a hut. There were rats running through the hut, and some dead rats on the floor. He tells you that his symptoms began on the day he flew back to New York city five days earlier. The patient receives symptomatic treatment and blood samples are taken. Considering his travel history and his symptoms the hospital staff suspect a viral hemorrhagic fever. By the fifth day after admission, conjunctival, nasal, and oral petechial hemorrhages are evident and three hospital staff and two other patients in the ward become ill with similar symptoms and one later dies. The traveler MOST LIKELY was infected by
A. smallpox virus.
B. yellow fever virus.
C. a non-enveloped small DNA virus.
D. Lassa fever virus.
E. Dengue virus.
D
Major clues: Traveler’s history; West Africa, along with clinical signs. Rural village with presence of rats/dead rats. Most likely ‘viral’ cause of his hemorrhagic fever is Lassa fever which is present in this location, has incubation period consistent with case (5 to 21 days) and is transmitted by rodents via aerosol/contaminated dust.
Ans (A) is incorrect for many reasons such as smallpox has been eradicated and the patient recovered with no vesicular lesions; (B) and (E) are incorrect because both yellow fever and dengue are transmitted by mosquito vectors and this unlikely to occur in the NYC hospital. Ans (C) is incorrect because no small non-enveloped DNA virus is known to be associated with this disease scenario.
poxviruses
size?
composition?
genome?
features?
Size: BIG brick-shape particle
Genome (very large): Double-stranded, linear DNA. The only DNA virus that replicates solely in the cytoplasm
Largest and most complex virus; resistant to inactivation
poxvirus replication is under what type of regulation?
how does this work?
temporal regulation
vaccinia virus RNA polymerase requires a separate set of virus-encoded proteins for the transcription of the early, intermediate and late classes of genes
**early mRNA creates early enzymes and intermediate transactivators; intermediate mRNA creates late transactivators and late mRNA
small pox transmission
- Spread by secretions from mouth & nose and by pocks or scabs
- Thus, transmission requires close contact with patients or their clothing or bedding
a disfiguring disease?
small pox
progression of smallpox rash
day 1 - a few papules/raised spots (2-4 days after a fever); seen first on the face then on the body
day 2 - more papules; differ in size but same appearrance
day 3 - beginning of vesicles (fluid accumulation and raised)
day 4 - distinct vesicles; firm to touch; when broken dont collapse since fluid is in multiple compartments
day 5 - flluid is cloudy and looks like pus; pocks are now called pustules; fever rises and feeling more ill
day 7 - obvious pustules; all similar appearring; no mistake in diagnosis
(picture shows day 4,5, and 7)
day 8/9 - pustules are firm and embedded
day10-14 - pustules dry up and dark scabs form; scabs contain LIVE smallpox virus; patient is infective until all scabs have fallen off
day 14-20 - by day 20 all the scabs are off and light colored areas are observed; skin returns to normal over a week, however scars may remain for life
when are smallpox patients infectious?
scabs contain LIVE smallpox virus; patient is infective until all scabs have fallen off
where are lesions/pustules distributed in small pox?
face, palms/soles and extremities
less dense on the trunk
chicken pox vs small pox lesion distributions
in smallpox they are present on the palms and soles (denser on extremities)
in chickenpox, they are NOT (denser on body, fewer on extremities)
small pox diagnosis
gentian violet stain –> Guarnieri bodies (typical inclusions).
Electron microscopy –> brick shaped virions.
5 features that make a virus suitable for eradication
- No animal reservoir.
- Lack of recurrent infections.
- One or few stable serotypes.
- Availability of an effective vaccine.
- Absence of subclinical infections.
smallpox vaccine
made from vaccinia
contains live virus; similar virus but doesnt cause smallpox
can have bad side effects
human vaccinia immune globulin (hVIG)
used to treat adverse reactions from vaccinia (smallpox vaccine)
