Sketchy Flashcards
Rhinovirus (Picornaviridae)
Rhinovirus (Picornaviridae)
Naked virus
Transmitted through inhalation
Unique among corona viruses b/c it is acid-labile (cannot go through GI tract, therefore cannot be transmitted fecal-orally like rest of Picornaviridae)
Transmitted through fomites
Rhinovirus enters host cell by attaching to ICAM-1
Rhinovirus grows best at cooler temperatures (33 degrees Celsius). Upper respiratory tract is cool.
Rhinovirus only affects Upper Respiratory Tract.
113 different serotypes so making vaccine is difficult (none for common cold)
No anti-viral treatments
Rubella Virus (Togaviridae)
Rubella Virus (Togaviridae)
Positive sense RNA virus
All Positive sense RNA viruses replicate in cytoplasm (outside nucleus)
Also called German Measles
Childhood exanthem
Togaviruses are enveloped
Togaviruses (and coronaviruses) produce one long polyprotein precursor that is cleaved by both viral and host proteases.
Buzzword: Immigrant
Congenital Rubella
Congenital Rubella
- TORCH infection so can cross placenta and affect fetus in utero
- Classic Triad: Congenital cataracts, Sensorineural deafness and PDA
- Mental retardation, Microcephaly, Deafness, Blindness, Cataracts, Jaundice, PDA, Pulmonic Stenosis, Purpuric Blueberry Muffin Rash, Radiolucent bone lesions
Rubella in Childhood (Transmitted via Respiratory Droplets)
Rubella in Childhood (Transmitted via Respiratory Droplets)
- Tender, postauricular and occipital lymphadenopathy
- Maculopapular rash that begins on face and spreads downwards
- Mild fever, lymphadenopathy and fatigue
- Rash progresses faster than measles rash and doesn’t darken or coalesce. Lasts for 3 days.
Adult Rubella
Adult Rubella
- Lymphadenopathy and fever
- Arthralgia and Arthritis
- MMR vaccine (live, attenuated vaccine that induces both humoral and cell-mediated immunity). Do not administer to pregnant or immunocompromised. Delay pregnancy one month to reduce transmission to fetus. Withhold from HIV pts until CD4 count is high enough (>200).
Coronavirus:
Coronavirus:
Positive, single stranded RNA virus
Encapsulated
Helical virus
SARS
Common Cold
Middle East Respiratory Syndrome (MERS)
Acute bronchitis that can lead to acute respiratory distress syndrome
Diagnose SARS by testing for antibodies or confirming with PCR. Negative clinical finding if absence of antibodies for 28 days.
Treatment: Broad spectrum antibiotics, Ribavirin or Corticosteroids
Replicates in cytoplasm (like all other SS RNA viruses)
Antigenic Drift:
Antigenic Drift:
Point mutations in the viral genome leading to changes in the hemagluttinin (HA) or neuroaminidase (NA) molecules. Cause epidemics.
Example: Seasonal Flu
Antigenic Shift:
Antigenic Shift:
Occur when antigenic segments of RNA are shared between different species. HA and NA can combine to form a new virus that is a mixture of the surface antigens. Segment reassortment. Responsible for pandemics.
H1N1
H1N1: Pandemic in 2009. Swine Flu. Result of antigenic shift between human, avian, and swine influenza viruses.
Influenza A: causes epidemics and pandemics.
Influenza A:
Influenza A: pandemics and epidemics. Antigenic drift and shift.
Influenza B:
Influenza B: endemic outbreaks. Antigenic drift.
Hemagglutinin (HA):
Hemagglutinin (HA): Specific glycoprotein on the surface of influenza viruses which binds to sialic acid found in membranes on cells of upper respiratory tract or red blood cells.
Causes RBCs to clump together
H1, H2 and H3 are HA antigens in influenza viruses that infect humans. Determines cell tropism (which cells virus can bind to).
Anti-HA antibodies are the same antibodies that protect you from the same strain in the future.
Influenza Virus Entry
Influenza Virus Entry:
HA binds to sialic acid on cell membrane
Virus endocytosed into cell
M2 protein (proton channel) creates acidic pH for viral uncoating (theoretically can prevent viral uncoating and replication by inhibiting M2; Mechanism of Amantidine and Remantidine).
Note: Influenza B lacks M2 protein
Amantidine no longer used for influenza due to resistance. Current use is for Parkinson’s to increase dopamine release.
Virus replicates in cell nucleus
Viruses become bound to host cell after replication through same sialic acid residues that HA was initially bound to
Neuraminidase (NA) cleaves sialic acid to release the newly formed virions from the host cell
Note: TamiFlu = Oseltamivir/Anamivir is NA inhibitor. Prevents virion release.
Administering after 72 hours will not be effective because the virions have already been replicated and released.
Influenza Vaccine
Flu Season: Dec. to Feb.
Administer influenza vaccine in Oct. for sufficient immune response before exposure
Live attenuated nasal spray
Injectable killed form
Trivalent form made from two A strains and one B strain
Quadrivalent form made with two strains of A and two strains of B
Children can receive vaccine after 6 months of age
Classic Presentation for Pneumonia secondary to Influenza
Classic Presentation for Pneumonia secondary to Influenza
Old person
HPI suggests flu: Myalgias, Fever, week-long non-productive cough
Mild improvement before productive cough and fever onset
Ill-Appearance
What is a major complication of influenza?
Pneumonia is a major complication of influenza.
Staph aureus is common culprit of bacterial superinfection
Strep pneumoniae can also be responsible
Reyes Syndrome
Reyes Syndrome
Child presents with fever, rash and vomiting
Mother administers aspirin for flu
Aspirin is contraindicated in children with viral illness
Life-threatening complications including liver failure and encephalitis
Aspirin uncouples oxidative phosphorylation
Note: Uncoupling agents disrupt the proton gradient along ETC.
This occurs in hepatic mitochondria in Reye’s Syndrome
Extensive damage to organelles visible under microscope
What is a major complication of Influenza A?
Guillain-Barre is major complication of Influenza A
Ascending paralysis (starts in feet and moves upwards)
CSF: High protein with low WBC (albuminocytologic dissociation)
Influenza Virus (Orthomyxoviridae)
Influenza Virus (Orthomyxoviridae)
Enveloped
8 virus segments
Spread via respiratory droplets
Flu season: Dec. to Feb. Vaccine administered in Oct. to build adequate immune response prior to virus exposure.
RNA negative so need to be transcribed into a positive strand using its own RNA polymerase
RNA negative so single stranded
All RNA viruses replicate in cytoplasm except Orthomyxoviridae, which replicates in nucleus
Paramyxoviridae:
Paramyxoviridae:
Negative-sense RNA Virus
Since it is an RNA virus, it replicates in the cytoplasm
Note: Exception is orthomyxovirus
Paramyxoviruses are enveloped
Spread by respiratory droplets
MMR: Live, attenuated vaccine (contraindicated in pregnancy)
Measles = Rubeola
Measles = Rubeola
4 C’s: Cough, Coryza, Conjunctivitis, Koplik Spots
Coryza = runny/stuffy nose caused by upper airway inflammation
Koplik Spots = Small, bluish white spots on red background found on buccal mucosa near second molars. Followed by itchy confluent maculo-papular rash. Originates from back of ears then spreads to face and neck before traveling to rest of body.
High fever (Over 40 degrees centigrade) that lasts 4 days
Major complications
Bacterial/Viral Pneumonia
Subacute sclerosing encephalitis (SSPE): Inflammation and sclerosing of the brain caused by persistent measles infection.
Classic Encephalitis Presentation
Classic Encephalitis Presentation
Pt had measles as a child or immigrated (never been vaccinated)
5-15 years later personality changes, seizures, myoclonus, ataxia, and eventually coma/death
Anti-measles antibodies in CSF for diagnosis but no effective treatment
Virulence Factors in Paramyxoviridae
Virulence Factors in Paramyxoviridae
HA
NA
Fusion proteins: Multinucleated giant cells (syncytia). Present in measles.
Fusion Protein in Measles
Fusion protein: multinucleated giant cells (syncytia)
Formation of Warthin-Finkeldey cells
Found in lymphoid tissues
