Arboviruses, Rubella Flashcards
arbovirus characteristics
RNA, single stranded, plus stranded, enveloped, icosahedral
how are arboviruses transmitted?
via blood sucking arthropod hosts (mosquitos and ticks)
difference between intrinsic incubation and extrinsic incubation
intrinsic- incubation in humans- usually 1 week
extrinsic- inside the arthropod, virus is not infectious until 14 days. arthropod is then infected for life
in the USA, what is the only serious disease concern stemming from arboviruses?
encephalitis
can you get human to human transmission?
not really- not unless blood transfusions
describe the progression of arboviral encephalitis
incubation is 1 week
viremia occurs quickly. virus multiplies in vascular endothelium.
causes febrile malaise followed by encephalitis, paralysiss, coma and death
what is the treatment for arboviral encephalitis?
none
describe eastern equine encephalitis (EEE) and western equine encephalitis
togavirus-
RNA, ss, +, enveloped, icos
associated w/ focal outbreaks in summer months, usually near swamps or after rainy seasons
horses and humans are dead-end hosts- usually die before can infect mosquitos
instead, the virus is maintained in nature via transmissions between mosquitos and birds, neither of which develop symptoms
west nile virus
flavivirus
RNA, ss, +, enveloped, icos
most common cause of arbovirus in US. imported from egypt recently, now in every state.
maintained by bird-mosquito cycles. humans are dead end hosts. most fatal cases are in elderly
st louis encephalitis
flavivirus
RNA, ss, +, enveloped, icos
antigenically related to west nile, native to US. most fatal cases in elderly
dengue fever
arbovirus- flavivirus
RNA, ss, +, enveloped, icos
4 types
incubation period 1 week- humans are not dead-end hosts
fever, severe headache, muscle and joint pains, rash
what are the symptoms of dengue fever
fever, severe headache, muscle and joint pains, rash
dengue hemorrhagic fever
more severe form, notable for hemorrhage, vomiting blood, and shock
caused w/ sequential infections of cross reacting dengue fevers result in excessive inflammation and vascular permeability
yellow fever
arbovirus- flavivirus
RNA, ss, +, enveloped, icos
causes fever, nausea, jaundice, hemorrhage
extensive multiplication in liver, spleen, and kidneys
how are yellow fever and dengue transmitted?
human-mosquito-human-mosquito
in the jungle, monkeys can also become infected w/ yellow fever and serve as a resevoir from which we can get infected
yellow fever vaccine
live attenuated
zika
arbovirus, flavivirus
RNA, ss, +, enveloped, icos
causes a mild form of dengue, may cause microcephaly
what defenses does a fetus have against viral infection?
placenta maternal IgG fetal IgM interferon cell mediated immunity?
parvovirus B-19 characteristics
DNA, single stranded, unenveloped, icos
how is parvovirus transmitted?
through respiratory tract or transplacental
what is the parvovirus incubation period?
14 days
what are the symptoms of parvovirus?
asymptomatic
or
fever, malaise, erythema infectiosum (slapped cheek), transient athritis
where does parvovirus replicate?
RBC precursors- causes lack of new RBCs for a week, which is tolerated fine normally
transient aplasic crisis- person w/ anemia infected with parvovirus has severe deficit in O2 carrying ability
hydrops fetalis
transplacental infection during first or second trimester can cause death w/ severe swelling
