Microbiology: RNA Viruses Flashcards
Where do all RNA viruses replicate?
In the cytoplasm
- except for retroviruses and influenza viruses
Poliovirus
A picornavirus which targets the intestines and then spreads to the spinal cords overtime.
A single stranded, (-) sense, linear RNA virus that possess a icosahedral capsid
- uses RNA poly and ribosome in host oropharynx and small intestinal cell cytoplasm
Enjoys motor neurons the most, so if possible, will spread via hematogenous routes to muscles and then retrograde up motor neurons
- if it infects motor neurons, causes inflammation that in turn causes irreparable damage to the motor neurons, causing decreased signaling and trophic (growth) factors to trunk/limb muscles.
Primarily affects children <5
- spreads via fecal-oral transmission and contaminated food/water
- also spreads via respiratory droplets
Complications:
1) bulbar polio:
- infects CN9/10/12 which causes difficult speak/swelling and sometimes breathing (if phrenic nerve)
2) post-polio syndrome
- extensive loss of muscle function due to collateral branches that were made at the time of infection, now dieing off due to old age.
3) Aseptic meningitis
4) General polio:
- usually asymptomatic (99% of the time)
- high fevers/asymmetric paralysis/intense muscle pain
- “floppy baby syndorme”
- difficulty breathing and death
5) Vaccine-associated paralytic polio (VAPP)
- 1:1,000,000 chance that the attenuated vaccine strand mutates and causes paralytic polio
- usually affects close contacts and can cause outbreaks (usually only hurting unvaccinated patients)
Diagnosis
- stool or throat swab showing antibodies/polio
- lumbar puncture shows increased WBCs and polio RNA
Treatment:
- supportive treatment only
- vaccine (IPV (inactived)) or ORV (oral))
Rhinovirus
Common cold
A Picornavirus which targets the upper respiratory tract
- causes URTs and rhinitis
- cannot infect GI tract since it is acid-labile* (only picornavirus that is this way)
- also CANNOT cause aseptic meningitis
Is a single-strand, (+)-sense, RNA virus that is non-enveloped but has a icosahedral capsid
Is transmitted via respiratory droplets. Most common in <5yrs, >60yrs, immunocompromised or already having a respiratory condition
Uses the ICAM-1 receptors on respiratory epithelium cells in the host. This allows the virus to get in and replicate in the cytoplasm of the host cells
- causes immune reaction = inflammation = runny nose and rhinitis
Possible symptoms: Common cold
- nasal congestion
- sneezing
- sinus/head/ear/face pressure
- (+/-) loss of smell/taste
- fatigue
- malaise
- sore/irritated throat
- coughing
Diagnosis:
- usually diagnosed by symptoms without complications of concerning physical findings
Treatment:
- symptomatic treatment
- OTC = NSAIDs, nasal decongustants, 1st gen anti-histamines
Difference between (-) and (+) sense RNA viruses
(-) =. Needs to be encoded into mRNA 1st then sent to ribosome’
- needs host RNA polymerase
(+) = already mRNA and can go straight to ribosome
- does not need host RNA polymerase
Influenza virus
FLU
Is a orthomyxovirus
Single stranded, (-) sense RNA virus that possess a helical capsid
- has 8 segments* (makes for easy and rapid genetic shifts, hence why a new vaccine is need every year)
Uses hemagglutinin (H) (binds to sialic acid on host upper respiratory cell membranes and allows entrance) and neuraminidase (N) (promotes progeny viron release once replicated) to run its life cycle.
3 types (based on subtype of subtypes of H and N on virus capsid)
1) type A
- most common in humans
- 8 segments
- mutates often (most common for genetic drift and antigenic shift)
- most dangerous
- includes H1N1, H3N2
2) Type B
- less common in humans
- rare mutation
- 8 segments
3) Type C
- least common
- very rare mutation
- 7 segments
- uses fusion hemagglutinin proteins
Symptoms: 1-2 weeks long
- headache
- fever
- runny nose
- sore throat
- cough
Complications: (most common in: <6 months, >65yrs, pregnant women, chronic health conditions)
- pneumonia
- otitis media
- bronchiolitis
- reye syndrome (only when taking aspirin in children)
- croup
- sinusitis
- fatal bacterial superinfection (via co-infection from S. Aureus, S. Pneumoniae, and H. Influenza
Diagnostics:
- rapid flu test
- viral cultures
Treatment:
- symptomatic treatment
- neuraminidase inhibitors (Oseltamivir and zanamivir)
- only for at risk populations
2 vaccines:
1) trivalent inactivated influenza vaccine (TIV, goes into muscle and is killed)
2) Live attenuated influenza vaccine (LAIV), goes into nasal cavity and is attenuated)
How are RNA flu viruses named?
(Type (A/B/C)) / (Original host/vector) / (location of origin) / (strain #) / (year of origin) / (subtype)
Difference between antigenic shift vs genetic drift
Drift = random mutation in the hemagglutinin/neuraminidase protein genes
- causes minor changes and is primarily the reason why people need new vaccines every year
- is not a new strain of virus
- very common
Shift = infection of one host/vector cell via 2 different segmented viruses that combine to allow infection in a new vector/host
- causes complete RNA segment reassortment and development of a completely new strain of virus
- causes major changes and results in pandemics
- rare
“Sudden Shift is more dangerous than graDual Drift”
What are side effects of influenza vaccines?
1) egg allergies (the virus is cultured in eggs)
2) Guillain-Barré syndrome (rare, but possible)
3) children under 6 months will likely die due to very weakened immune system
- must make caregivers are vaccinated
Coxsackievirus
A picornavirus that is most commonly associated with hand/foot/mouth disease and herpangina
- Also can cause aseptic meningitis, myocarditis and pancreatitis
Coxsackie virus A serotype is the most common
Risk factors:
- poor hygiene
- age <10yrs
- most common in spring and summer
Symptoms of HFMD: - mouth/foot pain - dysphagia - mild fever - lethargy - oral enanthem (tongue/buccal mucosa) - exanthem on hands/feet/buttocks/legs/arms (macular, nonpruritic, non painful rash on locations)
Symptoms of herpangina:
- acute onset w/ high fever
- (+/-) febrile seizures
- anorexia
- irritability
- malaise
- dysphagia
- abdominal pain
- papulovesicular lesions on throat
- neck stiffness w/ (+) kernig sign
Treatment:
- NSAIDs and fluids
- no antiviral therapies
- treat complications as necessary
Measles virus
Rubeola
A paramyxovirus that is extremely contagious and kills children that aren’t vaccinated
- is not RUBELLA
Single stranded, (-) sense RNA virus.
Spreads via respiratory droplets and 90% of non-immune people are going to be infected if they come in contact with an infected proteins
Contains F proteins and H (hemagglutinin) proteins which allow entrance into host cells and fusion to form multi-nucleated cells in the respiratory epithelium
Symptoms:
14 days after infection
- high fever*
- conjunctivitis*
- coughing fits*
- Coryza (stuffy nose)*
- “Koplik Spots”* (enanthem rash on mucus membranes inside buccal tissue, opposite the molars)
17 days after infection
- Cephalocaudal Exanthem* = red blotchy maculopapular rash that spreads cephalocaudal direction.
21 days after infection
- persistent coughing only (recovery phase)
- is most contagious from 14 days - 21 days*
- once you recovery, you gain lifelong immunity*
complications:
- pneumonia (common cause of death in children untreated)
- diarrhea
- encephalitis
- subacute sclerosis panencephalitis* (occurs 7-10 yrs after infection for children under 2 at time of infection, idiopathic cause, but often fatal)
- suppresses immune system and causes bacterial superinfection (most common cause of death w/ infants infected)
Treatment:
- palliative care
- vitamin A supplements* (especially for malnourished)
- palivizumab* (blocks F protein and prevent pneumonia complications. Only for immunocompromised and children who develop complications)
- vaccine (household contacts and pregnant/infant populations)
What receptors does Hemagglutinin (H protein) bind to on host cells?
CD46 = found on all nucleated cells
SLAM = B/T cells and APCs
Nectin-4 = epithelial tissues
Mumps virus
Is a paramyxovirus that is super infectious and most commonly seen in children
Spreads via respiratory droplets and only has humans as hosts.
Single-stranded, (-) sense RNA virus
- possesses its own RNA poly*
- contains F and H proteins to attach and fuse into host cells/ fuse host cells together to form multinucleated giant cells in respiratory cells
Highly favors parotid salivary gland tissue (idiopathic reason)
Symptoms:
- Parotitis* (swelling/inflammation of parotid gland (can be unilateral or bilateral))
- Orchitis* (swelling/inflammation of testies (can be unilateral or bilateral))
- ear aches
- trismus* (spasms of the muscles of mastication, usually byproduct of parotitis)
Complications:
- encephalitis
- aseptic meningitis
- pancreatitis
- glomerulonephritis
can cause sterility in men
Treatment:
- symptomatic and palliative care only
- vaccine (usually makes it a non-factor in immunized populations)
What are the 4 Cs of measles?
Conjunctivitis
Coughing
Coryza (stuffy nose)
“C”polik spots (bright red spots with bluish-white centers that are usually opposite molars on buccal tissues)
Croup
Acute laryngotracheobronchitis
An infection caused by parainfluenza viruses from the paramyxovirus family
- almost exclusively affects children
contains F and H proteins to attach and fuse into host cells/ fuse host cells together to form multinucleated giant cells in respiratory cells
single stranded, (-) sense RNA virus
- has its own RNA poly*
- is enveloped
Spread via respiratory droplets
Risk factors:
- children 6 months - 3 yrs
- congenital respiratory issues
- history of intubation of hospitalizations for respiratory illnesses
Symptoms of croup:
- abdominal pain/myalgia
- fever
- seal-like “barking” cough*
- (+) steeple sign on x-ray (narrowing of trachea)
- Inspiratory stridor*
- hoarse voice
- pulses paradoxus due to upper airway obstruction* (severe only)
Treatment:
- oral corticosteroids (dexamethasone, 1st line)*
- racemic epinephrine nebulization* (only if corticosteroids fail)
Respiratory syncytial virus
RSV virus
Is a paramyxovirus that is Primary cause of bronchiolitis in small children
- due to airways being smaller, so inflammation has profound effects
Single strand, (-) sense RNA virus that is enveloped
- contains own RNA polymerase
Contains F and H proteins to attach and fuse into host cells/ fuse host cells together to form multinucleated giant cells in respiratory cells
Spreads via respiratory droplets and often presents with “air-trapping” (over-inflating)
- leads to hypoxemia
Symptoms:
- similar to cold at beginning (congestion, sore throat, coughing)
- dyspnea
- wheezing
- fever
- tachycardia and respiratory exhaustion (severe cases only and requires hospitalization)
- central apnea (intermittent short periods of no breathing)
kills via causing severe pneumonia if not treated
Risk factors:
- winter time
- children <10 yrs
- premature birth
- children who have NMJ disorders
Treatment:
- supplemental/palatative treatment
- palivizumab* (for immunocompromised and severe cases only to prevent o pneumonia)
