Microbiology: RNA Viruses Flashcards
(39 cards)
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)
Yellow fever virus
A flavivirus that is transmitted by Aedes mosquitoes found primarily in African/South America regions and jungles as well as the Congo river
- can affect primates also.
Single stranded, (+) senses RNA virus
- is enveloped
- icosahedral capsid
Attracts APCs and hitches a ride on immune cells in lymph nodes. There it replicates itself and bursts through host cells. Ends up in the blood stream and travels to hepatocytes and kidney cells where it replicates even further
Symptoms:
- often asymptomatic until after 3-5 days incubation period*
- extreme jaundice*
- extreme fever
- severe headache
- black vomit*
- presence of “councilman bodies” on liver biopsy* (eosinophilic apoptotic granules)
- upper abdominal pain
- renal tubular damage/failure w/ absent urination*
- GI ulcers/hemorrhages*
- coffee black stool
- arrthymias and MIs*
has decent fatality rates
Treatment:
- symptomatic and pallatative care
- NO NSAIDs
- Acetomenaphen (if not jaundice)
- live attenuated vaccine is applicable (cant use in history of allergies to vaccines or immunosuppressive populations)
What viruses are in the flaviviridae family ?
Dengue fever
Yellow fever
Zika
West Nile virus
What viruses make up the paramyxovirus family and what is unique about the group as a whole?
Parainfluenza (croup and bronchiolitis)
Mumps
Measles
RSV virus
Metapneumovirus
- all 5 present with with F and H proteins which cause fusion of host cells into giant multinucleated respiratory epithelial cells and allows entrance*
- also all tend to affect children the most*
West Nile virus
A flavivirus that uses the female culex mosquito as a vector
- endemic to Africa (specifically Uganda), but can be seen anywhere
- uses pigeons as secondary vector for mosquitos
Single stranded, (+) sense RNA virus
- has a icosahedral capsid
- uses E2 capsid proteins to induce endocytosis from host cells
Symptoms:
- 80% is asymptomatic*
- fever
- chills
- rashes
- 1% is severe (usually immunocompromised in someway)*
- encephalitis symptoms
- meningitis symptoms
- course upper extremity tremors if meningitis* (only seen in West Nile)
Treatment:
- supportive care/palliative
- steroids/ribavirin (only if meningitis/encephalitis appear)
Zika virus
Is a flavivirus that is transmitted via aedes mosquito vectors
- endemic to South America
Single-stranded, (+) sense RNA virus
- icosahedral capsid
can also spread via sexual contact and blood transfusions
Immune system is actually pretty strong against it so the vast majority is asymptomatic. Patients who actually see symtpoms rarely see serious complications (<0.1%)
Symptoms:
- mild fever
- arthralgia/myalgia
- skin rash
- conjunctivitis
- headaches
Serious harm is seen in babies, specifically in the form of microcephaly birth defect. Pregnancy patients need to not travel to endemic regions and avoid mosquito exposure.
- seizures
- vision/hearing issues
- intellectual defects
Treatment:
- supportive care and palatative care
- acetaminophen
Coronavirus Disease-19
COVID-19
Is a coronavirus that is a SARS-CoV-2 virus
- most similar to SARS
- originated from bat vectors in China but now can infect humans via a idiopathic mutation
- spreads via respiratory droplets
Fatality rate is around 5%, but is likely going to be around 0.5-0.7% when all is said and done
The vast amount of cases are asymptomatic carriers (25-50%)
Mortality rates based on ages: 0-9 = <0.1% 10-19 = 0.2% 20-29 = 0.2% 30-39 = 0.2% 40-49 = 0.4% 50-59 = 1.3% 60-69 = 3.6% 70-79 = 8% 80+ = 15%
Comorbidities associated with increased mortality with COVID
- HTN
- diabetes
- Cardiovascular disease
- Chronic respiratory disease
- Cancer
Symptoms:
80% show mild symptoms such as:
- cough
- cold like symptoms
20% show more severe symptoms such as:
- fever
- chronic cough
- dyspnea/chest pain
- fatigue
- loss of smell and taste
- pneumonia*
- kills via ARDS, CHF and septic shock only seen in serious cases especially if left untreated or develop pneumonia*
- in infants/young children , can very rarely cause Pediatric inflammatory multisystem syndrome (PIMS), which cases heart vasculature to be inflamed and dilate leading to unstable angina and MIs*
- in young adults, increases risk of stroke and can develop pulmonary fibrosis*
Treatment:
- supportive care and palliative care
- remdesivr* (not great data but is believed to shorten duration of symptoms (cant cure though). Can be used in hospitals for severe cases)
Dengue virus
Dengue fever/break-bone fever
Is a flavivirus that uses Aedes mosquitos as a vector
- endemic to African regions
4 serotypes DENV1-4
- IgG response to specific serotype = lifelong immunity
(if you have a good immune system and catch this and survive, you are immune to that serotype)
- there is no cross-protectively between serotypes (can catch all 4 if stupid unlucky)
DENV2 can cause dengue shock syndrome (but usually only in immunocompromised)
Very easily disseminates and replicates in leukocytes/monocytes
- causes dengue hemorrhagic fever.
Dengue hemorrhagic fever symptoms:
- high grade fever (>38.5C)
- generalized pain all over the body (especially eyes, joints, and abdominal)
- nausea/vomiting
- mucosal hemorrhaging
- fingernail hemorrhages
- cutaneous hemorrhages
- thrombocytopenia
- systemic rash
- respiratory distress
- ascites
- pleural effusions
- shock (sever eonly)
- encephalopathy (rare)
Diagnosis:
- presence of thrombocytopenia and increased hematocrit
- travel to endemic regions recently
- (+) antigen/IgM/IgG assays (5,3,7 days after infection respectively)
- (+) tourniquet test (inflate blood pressure cuff to halfway between diastolic/systolic pressures. hold for 5 minutes. Release and check for petechiae, positive = 10+ petechiae within 1 inch radius)
Treatment:
- no cure
- fever, shock and bleeding control and palliative care only
What is the only flavivirus that has a vaccine?
Yellow fever
- is a live, attenuated vaccine.
Rotavirus
Is a member of reovirus family
- Most common cause of viral gastroenteritis in children/infants*
- usually under 5yrs
- most common via group A strains of rotavirus
- most common in winter seasons in non-tropics
- common year round in topics
- common in daycares and schools
Segmented double-stranded RNA virus*
- double icosahedral capsid*
- uses RNA-dependent RNA poly.
Destroys villi/ microvilli (“brush border”) in the small intestine*
- decreases maltose and lactase enzyme activity (leads to temporary lactose intolerance)*
- does this via non-structural protein 4 virulence factor*
- leads to decrease absorption of sodium and potassium*
Symptoms: last 8 days usually, symptoms are usually only in children or immunocompromised
- vomiting
- watery diarrhea
- low grade fever
- can cause meningitis (usually only very young and not treated properly)
Treatment:
- palatative care and fluid hydration’s
- DONT use anti-diarrheal medications
vaccines are recommended for all children except those with history of Intussusception or SCID
