E1- Respiratory Infections Flashcards
ALL VIRUSES ARE ____.
Obligate intracellular parasites
Where do viruses reproduce?
Within living cells only
Why can viruses only reproduce in living cells only?
No independent metabolism
What is different about the reproduction of viruses compared to all other organisms?
No binary fission (use an assembly line process)
What is the goal of virtually all viruses?
Rapidly replicate new virion at the expense of the host cell
Does selective toxicity treatment work for viruses the way it can for bacteria?
Viruses use the hosts ribosomes, energy, precursor molecules etc. So, for example, when you kill the “viruses ribosomes” you also kill the hosts ribosomes.
What type of virus remains associated with the host, but it’s genes are largely silent?
Prophage (bacteria lysogens) or provirus (human host cell)
What is it called when a virus provides virulence factors such as toxins to a bacterial host?
Lysogenic conversion
What are the three main types of persistent viral infections?
Latent infections
Chronic infections
Transforming infections
What is it called when there is intermediating acute episodes of clinically evident virus production between which there is an absence of virus particles and limited viral macromolecular synthesis?
Latent infections (HSV)
What is it called when there is sustained nonlytic production of viruses, continued presence of substantial numbers of virus particles during period in which cLinical disease is absent?
Chronic infections (Hep B)
What is it called when infected host cells are “immortalized” and properties altered to those of cancer cells?
Transforming infections (HPV)
Why are viral infections so hard to manage?
- Exploit host cell functions (makes developing non-toxic chemotherapeutic agents challenging)
- Viruses can evade immune system
What is the key control strategy for managing viral infections?
Avoidance of infection
What is an upper respiratory tract infection that creates tracheal constriction below the vocal cords?
Croup
What are the most likely causes of croup? What else can cause it, but is less likely?
PIV type 1 > PIV type 2»_space;> RSV
How does coup present?
Fever, barking cough in children 6-18 months, worse at night
What is unique about PIV?
Non segmented
What is a complication of PIV?
Otitis media - viral infection sets the stage for bacterial superinfection (warn pt)
Parotitis
Why types of PIV show seasonal upsurge?
PIV type 1 and PIV type 2
Does life long PIV immunity exist?
No! Repeat mild infections occur
How does RSV present?
Cough, dyspnea, cyanosis, sometimes croup
What causes of the symptoms of RSV?
Inflammatory response to infection
IgE
T cells
What is used to diagnose PIV?
Direct viral isolation from throat swabs
Direct FAB test
How is RSV diagnosed?
Rapid antigen tests*
Nuclear acid tests
Serology
If treatment for RSV is needed, what can you use?
Ribavirin (severe cases)
What can be used as prophylactic tx for RSV for high risk pts?
Monoclonal immune globulin (Palivizumab)
What causes syncytia formation in PIV?
Novel fusion protein
What is the worst birth season for RSV and why?
3-4 months before RSV season because the mothers antibodies are no longer there
What is SARS?
Severe Acute Respiratory Syndrome, a highly fatal coronavirus that is now presumed to be exinct
What is the causative agent of SARS?
Coronavirus
What is MERS?
Middle east respiratory syndrome
What is the causative agent of MERS?
Coronavirus
Which viruses act as a zoonotic reservoir?
SARS and MERS
Why are respiratory tract infections so common?
Many are caused by viruses
-abx ineffective
-not many effective vaccines
Usually acute
-pts may infect others before showing sxs
Many transmitted from healthy carrier reservoirs
