Apr25 M1,2,3-Virology Flashcards
virus structure
nuclei acid core surrounded by a capsid (and some have an envelope around that)
how a virus infects a cell
attach to host cell Rs, is endocytosed, penetrates the membrane and assembles new particles. new particles released by budding or cell lysis
what happens during the incubation period
the virus replicates
how viruses can disseminate in the host body
- using nerves, to go towards the CNS
- bloodstream
transmission routes of viruses
- resp (droplet (big and limited distance), aerosols, saliva, nasal secretions)
- GI (fecal-oral)
- transcutaneous/transmucosal (arthropod borne diseases, blood-borne)
- vertical (mother to infant in utero)
examples of viruses transmitted via resp route (3)
- rhinovirus (droplets)
- influenza (droplets)
- RSV (droplets)
some viruses using GIT route (4)
- enteroviruses (enterovirus, coxsackie, echovirus, poliovirus)
- hep A
- norovirus
- rotavirus
common characeristic of viruses that use GI route
- DON’T have an envelope
- survive stomach acid, bile, proteolytic enzymes (resp viruses don’t survive that)
some viruses using the transcutaneous route (animals, insects, needles)
- arboviruses (Dengue, West Nile, Zika)
- HepB
- HIV
- Rabies (from bat)
some viruses using the transmucosal route and their mode of transmission
- CMV
- HepB
- HSV
- HIV
- are sexually transmitted*
some viruses using vertical transmission
- viremia and infection of placenta = rubella (is a congenital disease), CMV, parvovirus
- exposure in birth canal = HSV, HIV
4 ways to dx a virus (and main one used)
- tissue culture (cell lines, embryonated eggs, suckling mice)
- antigen detection (ELISA, immunofluorescence)
- nuclei acid detection (in-situ hybridization, PCR)** MAIN ONE **
- serology (IgM+, 4x rise in acute and convalescent IgG (sera)
how virus (resp virus for ex) is detected on tissue culture (cell lines of fibroblasts or cancer cells for ex)
- inoculated on a monolayer
- don’t see virus
- see monolayer going from orgnized to disorganized, death, refractory nuclei = CYTOPATHIC effect
most common use of embryonated eggs for virus tissue culture
- influenza virus (to grow in high titer)
- inject allantoic fluid with a respiratory specimen (secretion) and will check later to see if there’s a virus in there
monoclonal Abs (ELISA) for virus dx is used for what viruses
- RSV
- adenoviruses
- influenza
- rotavirus
PCR (main virus dx technique) method and used for what viruses mainly
- take specimen (like sputum)
- use probes of all diff viruses
- do PCR
- mainly for respiratory viruses*
serology testing for virus dx: method
- acute infection is IgM+, IgG-
- weeks after infection = IgG+
orthomyxoviridae = what viruses
influenza A,B,C (C = no disease in humans)
paramyxoviridae = what viruses
parainfluenza, RSV A and B, human metapneumovirus
adenoviridae = what virus
adenovirus
picornaviridae = what virus and disease
rhinovirus (common cold)
also enterovirus including coxsackie, echovirus, enterovirus, poliovirus. hepatovirus. parechovirus
coronaviridae = what virus and disease
coronavirus (cold, SARS = severe acute resp syndrome), middle east resp syndrom)e
viruses with a lot of serotypes
- rhinovirus (89, so recurrent infections, + immunity not lifelong)
- adenovirus (49)
- coronaviruses
(imp) RSV: 2 basic proteins
- G protein (for attachment)
- F protein (for fusion, with the host cell)
which population is particularly affected by RSV and disease caused
- children and especially newborns <6 mo
- 75% of 1 year olds are seropositive
- BRONCHIOLITIS
(imp) RSV exact transmission, symptoms and pathology
- resp droplets
- fever, coughing, wheezing, dyspnea
- inflammation in bronchioles: edema and mucous formation. severe resp distress in infants
in the newborns population, who is especially vulnerable to RSV (paramyxoviridae)
- premature babies (lungs less developed)
- congenital heart disease and shunting disease (have less cardiac reserve)
specific RSV prevention method given to vulnerable newborns
- prophylaxis monoclonal Ab to the F protein
- every month in winter time to high risk group of right age
- IM injections, cost 1500 each
virus shedding meaning
virus exocytosis, budding out of host cells
rhinovirus (picornaviridae) route of transmission, incubation period, shedding time, infectivity period, if is on surfaces
route = big droplets incubation = 1-4 days shedding = in days 1 to 3 infectivity = in first days infected lives on surfaces = yes
complications of rhinovirus infections
- sinusitis
- otitits media
- asthma
how immunity to rhinoviruses is maintained
an Ab develops to the serotype that infected you
adenovirus (adenoviridae) particular characteristics and route of transmission
- latent (dsDNA)
- no envelope so goes in GIT
- transmission = aerosol and fecal-oral (is a GIT and resp virus)
- many serotypes
adenovirus: diseases caused
URTI, LRTI, GE, keratoconjunctivitis, hemorrhagic cystitis
charact of adenovirus latency
- no problems unless immunocompromised
- problems in children who get BM transplant
- recurrent, prolonged shedding (as part of the latency)
clinical significance of adenovirus latency
- latent so vector for gene therapy
- inject adenovirus with a missing gene
- adenovirus multiplies and expresses this gene
coronavirus (coronaviridae) is like what virus
rhinovirus
coronavirus: diseases caused and important one
- URTI
- pneumonia
- SARS** (was caused by a recombinant mammalian and avian CoV)
MERS-CoV (Middle East Respiratory Syndrome Coronavirus) source of the infection and mortality (related disease)
- camels infected with the virus
- 40-50% mortality (severe respiratory illness)
influenza virus original virus
originates from spanish flu
2 glycoproteins on influenza A,B and C
- hemagglutinin (H1, H2, H3)
- neuraminidases (N1, N2)
antigenic shift in influenza virus
antigenic shift = not common, when a new H and N numbered virus pops up after years of having vaccine for same strain (H1N1 before and now new H2N2 and lot more get sick
antigenic drift in influenza virus
- common
- same H and N but different strains (like diff H1N1 strains)
influenza symptoms, transmission and complication
- fever, myalgias, HA, cough
- droplets
- complication = bacterial pneumonia (associated are S pneumoniae and S aureus)
how influenza strains are generated
- birds are a big reservoir for influenza viruses
- birds transmit to other birds or swine (pigs)
- reassortment (strains recombination) happens in pigs and birds (mostly pigs)
- pigs and birds transmit reassortant virus to humans
2 types of influenza vaccines
- inactivated
- live, attenuated, cold-adapted (give live influenza that can only live in the cold as a nasal spray)
limit of influenza vaccine
- immunity (Abs) wanes over time
- a different virus circulates the next season
main characteristic of the herpes viruses category
DNA viruses so are latent
some viruses in the herpes viruses group
- HSV 1,2 (1 and 2 are equal)
- VZV (chickenpox)
- EBV (infectious mono)
- CMV
HSV transmission and what it does in the body
- direct inoculation of mucous membranes (mouth, eye, genital tract, etc.) (NOT skin)
- accesses nerve cel endings in epidermis and is transported to nerve cell bodies in peripheral ganglia to establish latency there
what does HSV do when it is reactivated
travels back down its route (down the peripheral nerves) and illness appears
herpes encephalitis is possible but very rare
consequence of HSV route of transmission and how it travels in the body
- destruction of epithelial cells in skin and mucous membranes
- nerve damage causing tingling and burning (prodrome)
HSV diseases caused
-ocular infection
-oral infection
-herpes keratitis
-genital herpes
-neonatal herpes
-encephalitis
-disseminated herpes
(2 last = newborns vulnerable if mom never infected)
treatment of herpes infections and what it really does
acyclovic
- reduces duration of symptoms
- doesn’t eliminate latency
VZV infection symptoms
- generalized vesicular rash (papular vesicular lesions) (starts in stomach and goes out whereas measles starts on head and goes down)
- fever
complications of VZV
- bacteria superinfection (GAS) (necrotizing fasciitis for ex)
- thrombocytopenia
- cerebellar ataxia
- encephalitis
clues to recognize varicella
- papules start on stomach then spread
- varicella papules are at different stages at the same time
VZV vaccine charact
- live vaccine (so giving latent virus for life)
- less risk of developing shingles Zoster
What is Zoster Shingles
- reactivation of varicella virus (spread to dorsal root ganglia)
- reactivated VZV on a dermatome
- painful
- happens if immunocompromised (elderly for example)
CMV how infects you and where it resides
- through epithelium
- persists in hematopoietic and epithelial cells
main problem with CMV
congenital infection (when a mother gets a primary CMV infection during pregnancy): baby born with a lot of defects (liver, spleen, small head, growth retardation)
CMV charact (when do we see symptoms and where is it when it reactivates)
- usually asymptomatic, otherwise mono-like
- immunocompromised = more significant infection (and symptoms)
- periodic reactivation in saliva, urine, blood
EBV enters body how and infects what cells + special charact
- enters through mucosal surfaces
- B lymphocytes and epithelial cells (viral genome persists in memory B cells)
- has an envelope
symptoms in most cases of EBV
sore throat, fever, fatigue, lymph nodes, possible whitish exudate on tonsils and big tonsils
complications of EBV
- B-cell immortalization and transformation (lymphoproliferative disease) in immunocompromised pts and posttransplant
- Hodgkin’s disease
- Burkitt lymphoma
- nasopharyngeal CA
viruses of gastroenteritis (GE) and link
- rotavirus
- enteric adenoviruses (conjunctivitis, diarrhea)
- norovirus
- astrovirus
- calicivirus
- all have similar presentations* + note all have no envelope
tx of GE
supportive tx
transmission of GE viruses
fecal-oral
rotavirus charact
- groups A to F. A is most common. same serotype reinfection is possible
- severe pediatric disease
- peak age of infection = 6 mo to 2 years
rotavirus symptoms and pathology
- fever, vomiting, watery diarrhea, dehydration
- atrophy of SI villi + carb malabsorption
rotavirus dx
Ag detection by ELISA. put stool on plate with rotavirus Ab. then add Ab with fluorescein marker to the 1st Ab
norovirus incubation and affects who
- 1-2 days incubation
- cruiseships, hospital ER staff
- outbreaks in schools
norovirus transmission
fecal-oral and aerosol (after vomiting)
norovirus evolution of illness
- acute onset of vomiting
- diarrhea for 24 hours
- total 48 hours feeling very bad
norovirus tx
(self limited illness)
-water, rest, symptomatic tx
viruses in the picornaviridae family
- rhinovirus (human rhinovirus)
- enterovirus (coxsackie A and B, echovirus, enterovirus, poliovirus)
- hepatovirus (hepA virus)
- parechovirus (human parechovirus)
enteroviruses
- enterovirus
- coxsackie A and B
- echovirus
- poliovirus
enteroviruses transmit how, spread where, replicate where
- transmitted fecal-oral
- replicate in GIT
- spread in blood to target organs
enteroviruses symptoms
- aseptic meningitis
- herpangina (sores in the mouth)
- hand, foot and mouth disease (coxsackie)
- myocarditis
- hemorrhagic conjunctivitis
echovirus: why called like that
Enteric Cytopathic (effect on tissue culture) Human Orphan (thought it caused no disease but wrong) virus
(imp) polio (an enterovirus) serotypes
1,2,3
(IMPORTANT) polio main concern
- invasion of brain and spinal cord + destruction of anterior horn cells
- get muscle INCLUDING DIAPHRAGM paralysis*
(IMPORTANT) 2 polio vaccines
- inactivated (Salk) = IPV
- Trivalent oral LIVE vaccine (Sabin) = OPV
(IMPORTANT) IPV charact
- need syringe, cold chain to keep it from degrading, someone competent to give it = in developed countries
- enhanced formulation. >99% benefit. few adverse effects
(IMPORTANT) OPV charact
- taken by mouth, gos down GIT.
- immune response similar to natural infection, is mucosal IgA mediated immunity
- developing countries (cheap, easy, effective)
(IMPORTANT) ‘‘Herd vaccination’’ in polio is what
- some people got OPV
- transmit it through fecal-oral route to people who didn’t get vaccinated
- these people are now vaccinated
(IMPORTANT) rare complication of polio (can happen in immunocompromised person)
VAPP (vaccine associated paralytic poliomyelitis)
= polio paralysis
rabies caused by what virus and in what animals
lyssavirus (is in dogs, terrestrial wildlife and bats)
how rabies is transmitted
-salivary contact with infected animal including breathing air (resp tract transmission) in bat caves
inoculation time (incubation) of rabies and why
- from days to years (avg 90 days) depending on infection site
- virus has to travel in peripheral nerves to reach CNS and lead to encephalitis
prodrome of rabies
- 4-10 days
- subtle neuro changes
- tingling at bite site
- headache, myalgia, flu like illness
CNS infection (encephalitis) with rabies consequence (symptoms)
- confusion, agitation, hydrophobia, aerophobia, throat spasms
- in <20% cases, progressive flaccid paralysis
* *very high mortality rate**
treatment of rabies
Milwaukee protocol
-drug induced coma
-antivirals
(still very high mortality rate. used o be 100% mortality)
rabies two ‘‘treatments’’ other than Milwaukee protocol
pre and post exposur prophylaxis
pre-exposure prophylaxis in rabies
human diploid cell vaccine, 3 IM doses. for high risk peopel (vets, travelers, spelunkers)
post exposure prophylaxis in rabies
- immediate wound care (providone-iodine)
- rabies Ig Ab injection in the wound
- human diploid cell vaccine (4 doses)
hemorrhagic fever viruses other name for these + 2 examples
filoviruses
- ebola
- Zika
reservoir of Ebola and transmission
- reservoir = fruit bats
- transmission = direct blood, secretions contact. contaminated needles
Ebola species with the highest fatality rate
Zaire ebolavirus
Ebola incubation time
2-21 days
Ebola evolution of symptoms
- 0-3 days: non specific illness (fever, headache, joint pain)
- 3-10 days: diarrhea, vomiting
- 7-12 days: shock or recovery
- > 10 days: late complications
hemorrhage is where in ebola
mouth, GIT, etc.
important component of Ebola illness
large diarrhea and vomiting
- electrolyte imbalance
- dehydration
- need to support, otherwise shock*
Zika virus is in what family of viruses
Flavivirus (includes Dengue, yellow fever, WNF = West Nile Fever, Japanese encephalitis)
(flavivirus for yellow, bc gives hepatitis, turns you yellow)
Zika virus previous and current locations
previous: Uganda, SE Asia, Pacific ilsands
current: Central and South America
Zika virus symptoms
fever, rash, arthralgias, conjunctivitis
Zika virus transmitted how
- Aedes aegyptus (fly). has visible stripes
- sexual transmission
dengue symptoms
- red rash for a week
- rarely, severe hemorrhage with high mortality
2 ways of dx Zika and Dengue and how to choose
- IgG and IgM testing (if never vaccinated for yellow fever)
- RT-PCR (if already got vaccinated for yellow fever, bc will test Zika positive. Zika and yellow fever are alike)
Zika vector, how Zika is transmitted other than by the vector and what body part does it infect
- Aedes aegyptus or sexual transmission
- intrauterine infections
main worry with Zika
associated microcephaly in newborns (small head)
Zika tx
- no tx or vaccine right now
- prevent mosquito bites and control mosquito breeding sites. this mosquito is active during the day. + man sperm infected so abstain for 6 months
