T2 - Micro - Virology 3 - Vector Borne Viruses

Front 1

what are the virus families that fit into the vector-borne virus idea?

Back 1

togavirus, bunya virus, flavirvirus. paul bunyan with a toga getting eaten by a mosquito due to flavor.

note that the togavirus world is divided into alpha viruses and rubivirus

Front 2

arbovirus encephalopathies - which viruses specifically cause the greatest number of cases? which is the most deadly?

Back 2

St. Louis encephalitis virus is one (flavavirus).

western equine encephalitis (alphavirus)

eastern equine encephalitis (alphavirus)

california

west nile virus (flavavirus).

note that EEE (eastern equine encephalopahy) is the worst - 70% of infected die. Luckily, only 7 cases/year in the US.

Front 3

talk more in depth about EEE -

Back 3

life cycle involves birds/mosquitos, before infecting horses/humans/mammals.

no vaccine for people, but there is for horses.

REMEMBER - the equines (west and east) are ALPHAVIRUSES

EEE is most severe, 70% fatal. Those who recover had permament effects.

Front 4

does replication in the vertebrate host of alphaviruses/flavaviruses (arboviruses in general) usually result in viremia?

exceptions are YELLOW and DENGUE - these cause viremia high enough to spread person to person (via mosquito vector) - no need for animal reservoir.

does replication of virus have to happen in the insect for it to be spread?

Back 4

no - not usually viremia in the the patient.


yes, replicaiton in the insect has to happen for spread to human.

Front 5

describe the structure of alpha viruses:


how do alpha viruses get into the cell?

Back 5

single stranded RNA, NEGATIVE STRANDED. Remember that the equine viruses are caused by these.



ALPHA - remember they use Class 2 adhesion proteins.

influenza uses class 1 (random fact).

can use EITHER endocytosis into an endosome OR direct fusion and dumping.

acidification of endosome makes virus envelope bind with endosome membrane and release of genome.

Front 6

talk about alpha virus replication -

what protein specifically did they mention has to be cleaved?

what cleaves our polyproteins?

Back 6

CAPSID is also PROTEASE and does viral polyprotein clipping.


alpha virus genetics bind to the ribosomes.

remember that the capsid is also a protease.

5' end binds to ribosome, makes NON STRUCTURAL PROTEINS.

also note random fact - post-translational poly protein processing can be done by the CAPSID? it's one of the stupid questions.
3' end has the structural proteins.

i think this is opposite to flavaviruses, in which the 5'end is structural and the 3' end is non structural

PE2 needs to be cleaved.

Front 7

what general diseases to the flavaviriade family cause?

Back 7

any of the "location" encephalopathies (west nile, st. louis, kjnjin, japanese).

also, fevers - dengue and yellow fever.

Front 8

first, let's talk about dengue virus - what does it look like?

Back 8

+ stranded, ssRNA virus. enveloped.

remember, it's the painful fever.

Front 9

any varieties of dengue? symptoms? vector? erridacation ideas?

Back 9

yes! 4 of them. each of them provides you lifetime immunity against each individual kind, and short-term cross protection. BUT NOT LIFETIME.

So, if you get type 1, you might be immune against 2,3, and 4 for awhile = but not forever. permamently immune to one.

symptoms - ACUTE ONSET - severe headache, myalgias/arthralgias, leukopenia, hemorrhagic symptoms. Sometime shock/fatal quickly.

mosquito vector - ades aegypi.

so don't forget - there's normal DF and DHF (hemorrhagic = minority)

now thought to be unable to eradicate in this hemisphere. Lack of money, lack of effective insecticides, low priority.

Front 10

how is dengue transmitted?

Back 10

our mosquito - aedes aegypti - comes in through saliva of bug, replicates in lymphatic tissues (monocytes/macrophages) - then circulates in blood.

new mosquito comes in, sucks up the viremic blood, replicates INSIDE the mosquito, in the salivary glands, then gets passed on to the next person.

Front 11

how can you tell dengue shock is setting on?

Back 11

when the fever goes away, see platelet drop/increase in crit. see shock syndrome - prolonged vomiting, abrupt change in fever, temp drop. 3/6 days from symptom onset.

Front 12

what's weird about dengue and antibodies?

Back 12

when you get infected with Dengue 1, you make both neutralizing and non-neutralizing antibodies against it.

The non-neutralizing antibodies stay around. When you get infected with Dengue 2, these non-neutralizing antibodies bind and help the virus get eaten by macrophages.

Unfortunately, this increases the chance the virus has to replicate inside the macrophages and is a bad thing. These complexes get magnified.

called "antibody enhancement"

Front 13

how do you clinically evaluate dengue? test for it?

Back 13

look at hydration/permeability of capillaries (fluid collection), blood pressure/bleeding sites. Petechiae.

tourniquet test - inflate cuff to between systolic/diastolic pressure. wait 5 minutes. count petechiache ( >20/inch = positive)

do normal blood tests (wbc, crit, etc).
also, do serology - isolate virus, elisa for Ab's, etc.

Front 14

how do you treat dengue?

vaccine?

Back 14

fluids. rest, non-NSAID antipyretics, monitor. Don't need to be giving aspirin to people who are bleeding inside themselves.

NO VACCINE approved yet. testing one now.

Front 15

yellow fever? what causes it? transmits it? life cycle?

Back 15

flavivirus - same mosquito vector (aedes aegypti) as dengue. female mosquito.

life cycle of the virus - in jungle, maintained in monkeys. in urban centers, maintained in people (like dengue).

Front 16

disease course of yellow fever?

Back 16

can be mild, fever/headache.

severe - fever/chills/bleeding into skin, back apins, prostration. constipation. JAUNDICE = yellow, sometimes receed, then come back worse.

delerium/coma/death.

Front 17

west nile virus? transmitted by? symptoms?

Back 17

birds, mosquito, back and forth. then from the mosquito to PEOPLE or HORSES.

also a flavavirus

there's a rash that goes along with this - maculopapular rash, then encephalitis.

Front 18

how's louisiana doing with west nile virus?

Back 18

327 human cases.

also have horses with EEE

Front 19

st. louis encephalitis virus? life cycle? what do most cases result in?

Back 19

also flavavirus.

maintained in birds and mosquitos, then to people.

no disease in animals - only human disease.

in healthy people, 2% death rate. 22% in elderly.

note that MOST INFECTIONS ARE INAPPARENT. basic flu symptoms if anything.

humans are dead end hosts.