Respiratory Viruses Flashcards
Where are most respiratory infections acquired
human to human. Rarely from animals, though they are dangerous if then they can jump person to person
Where do pure respiratory viruses stay?
Confined to the epithelial cells of the respiratory tract (Thus viremia can be absent even in the presence of severe disease)
What part of the respiratory tract do rhinoviruses attack
mostly nasal cavity and a little bit pharynx
What part of the respiratory tract do parainfluenza viruses attack
most larynx (laryngitis and croup) but a little bit pharyn and tiny bit nasal cavity.
What part of the respiratory tract does RSV attack
HUGE for bronchioles (bronchiolitis) specifically, a little bit nasal cavity
What part of the respiratory tract does influenza attack
Mostly Alveoli, a tad the bronchioles, and the nasal cavity a bit
What are the 3 manifestations of common cold
- rhinorrhea (runny nose)
- cough
- sore throat
What is the most common virus for common cold, how much does it account for?
50% of common colds are caused by rhinoviruses. There are 100 serotypes of it which is why we are always reinfected
How does rhinovirus evade immune response
the conserved receptor binding site (ICAM-1) is buried in a canyon on the viral surface making it inaccessible to antibodies
What are the 4 symptoms of bronchiolitis and time frame
first
- fever
- rhinorrhea
next
3. cough
4. wheezing
This second stage lasts for 1-2 weeks
What is major cause of bronchiolitis and what proportion
RSV causes 80% of the cases of bronchiolitis
Describe how the wheezing occurs
The bronchioles are small, flexible respiratory passages. inhalation - negative pressure pulls bronchioles open. exhalation - positive pressure pushes them shut trapping air in the alveolar spaces. This leads to wheezing noises
Classification of Rhinovirus
no envelope. icosahedral virus. non-segmented, + strand RNA. family: picornaviridae.
SIMILAR TO POLIO VIRUS
Classification of RSV
enveloped virus, non-segmented, -strand RNA
Describe the 5 sx of influenza
- constitutional sx (fevers, chills, malaise)
- myalgias
- headache
- sore throat
- cough
Classification of flu virus
enveloped. segmented. -strand RNA
Does RSV infection prevent re-infection
in short - no. It will reduce the rates of re-infection, but does not do it completely. It will also reduce the severity of the infection
What are the 3 flu viruses?
A - people to people. Can infect other mammals (pigs) and can get from domestic birds. can be severe. 8 segments
B - only in humans. can infect seals. mild sx. 8 segments
C - mostly kids only humans. 7 segments
Describe entry to host cell for influenza
hemagluttinin from virus binds to sialic acid on the host cell-surface. Endocytosis of the virus occurs.
How does the virus get into the cell nucleus
the virus is in the endocome and waits for the pH to drop. the M2 channel will allow H+ ions into the cell. This then lets the Ribonucleoprotein (RNP) release from the viral particle and into the endosome. Now the virus membrane will fuse to the endosome membrane and the RNP will be released into the cell cytoplasm. From there it is transported into the host cell nuclus.
What drug blocks this uncoating step of flu? how does it work
Adamantines will block the M2 channel and thus the RNP will never be released from the viral particle. This is only effective against flu A
What happens in the nucleus to the RNP (flu)
After the RNP is transported into the cell nucleus. The - strand is copied to a +strand. This strand does 2 things
- make more -strands for packaging in the new virions
- translation by the host cell to make new viral proteins
Where is the new flu virus assembled
At the membrane of the host cell
How does the virus then bud? What is crucial
The virus will then embed into the host cell and will bud off. However, because it has tropism for sialic acid, it has to stop from binding back to the host cell. To do this, the virus has a neuraminidase which will cleave the sialic acid residues from the host cell preventing it from getting stuck to the dying host cell.
What is the drug that works on flu viral budding
neuraminidase inhibitors stop release of the virus. They work against flu A and B.
How many H’s and how many N’s exist out there
1-16 H’s and 1-9 N’s
What is antigenic drift? What
point mutation in the H and N. Still have cross-reactivity, nonetheless
What is antigenic shift
When a new serotype arises. Happens about every 10-30 years. Reassortment occurs because the viral RNA is segmented
How many strains circulate every year
usually 2 A and 1 B
How does influenza lead to increased bacterial pneumonia
It kills (apoptoses) the ciliated epithelial cells that it infects weakening the mucociliary clearance.
What are the fates of influenza
- uncomplicated flu and recovery (very common)
- bacterial pneumonia (uncommon) and moderate mortality
- viral pneumonia (very rare) and high mortality
What is antigenic shift
When a new serotype arises. Happens about every 10-30 years. Reassortment occurs because the viral RNA is segmented
How many strains circulate every year
usually 2 A and 1 B
How does influenza lead to increased bacterial pneumonia
It kills (apoptoses) the ciliated epithelial cells that it infects weakening the mucociliary clearance.
What are the fates of influenza
- uncomplicated flu and recovery (very common)
- bacterial pneumonia (uncommon) and moderate mortality
- viral pneumonia (very rare) and high mortality
