common cold Flashcards
cold can be caused by
Rhinoviruses(grow best at a cool 33°C) Adenoviruses Enteroviruses (also are Picornaviruses) Coronaviruses Parainfluenza viruses( influenza virus grows best at warmer temperatures deep in lung.)
Rhinoviruses
RNA \+ss Pircornafamily Viruses: enter, polio, rhino, HAv Icos no envelope Cause release of histamine - symptoms IFN - symptoms Mucous - symptoms There are lots of serotypes of rhinoviruses.
Rhinovirus
- blocks IFN production:
less IFN symptoms than flu - largely controlled by IFN production
-Neutralizing antibodies are made weakly, so protection against
reinfection is weak.
Enteric viruses
Picornaviruses:
-Enteroviruses - spread via fecal-oral route but replicate mainly in lymph nodes
-Poliovirus - spreads to neurons in spine and kills them
-HAV - Hepatitis A virus: covered in Hepatitis virus section
(Rhinovirus is a picornavirus but it is is not an enteric virus - it’s a respiratory virus)
Rotavirus
Adenoviruses
These are all naked viruses.
Enteric Coronavirus - an enveloped virus
there are also non-enteric coronaviruses
such as SARS virus and MERS virus.
adenovirus
DNA
ds
gastroenteritis
cos no envelope
reovirus
RNA ds segmented rotavirus, reovirus gastroenteritis cos no envelope
picornavirus
\+ss entero, polio, rhino, hav gastroenteritis cos no envelope
coronavirus
RNA \+ss enteric coronavirus gastroenteritis local envelope
rotavirus
childhood diarrhea
Causes gastroenteritis
Intestinal inflammation, diarrhea, fever, vomiting,
mostly in children, can last up to a week.
Infect intestinal columnar epithelial cells.
Stool can contain up to a billion virions per mL - even during
asymptomatic infection
Virus remains infectious in water. <10 virions needed to initiate infection.
Babies reliably become infected once maternal
antibodies disappear.
There is a yearly sweep of rotavirus infection
from Mexico up through the US.
450,000 children die world wide per year
rotavirus
dsRNA virus - normally this would induce strong IFN response:
But the genome protected by THREE capsid layers.
The first capsid layer is removed by intestinal enzymes to make the virus
infectious.
Transcription happens in virions and ssRNA is squirted out to cytoplasm.
During viral assembly, ssRNA is packaged then turned into dsRNA.
This is all designed to hide the dsRNA from the innate immune system
to reduce the induction of IFN
Infected cells die, inducing innate immunity anyway but the virus has
had a head start by this time and has replicated and now can spread.
Antibodies come up late in infection, and virus is gone by the time they
are in full gear.
Antibodies mainly provide (incomplete) protection from reinfection.
polio
RNA \+ss Picornavirus entero-, polio, rhino- polio, cold, hepatitis Icos no envelope
polio
Spread by fecal-oral route
3 Serotypes of virus Types 1 - 3
Up to 95% of polio infections are asymptomatic but
contagious.
4-8% cause gastrointestinal disturbance.
1-2% temporary stiffness, weakness or paralysis in legs,
neck results, then resolves within ~10 days.
~1% of cases the virus enters the central nervous system,
infecting and destroying motor neurons, leading to chronic
muscle weakness and acute flaccid paralysis.
Recovery can be incomplete and take up to 2 years.
Poliomyelitis
Polio
Infantile Paralysis
Post-Polio Syndrome (PPS): 8-70 years after recovery from paralysis, fatigue,
weakness pain in areas involved at the time of acute poliomyelitis.
Etiology is not clear.
acute flaccid myelitis AFM
polio like symptoms
coxsackievirus A16, [as well as enteroviruses] EV-A71, and EV-D68 in the spinal fluid
AFM affects the gray matter of the spinal cord. Symptoms include rapid onset of arm or leg weakness and decreased reflexes.
Difficulty moving the eyes, speaking, or swallowing may also occur. Occasionally numbness or pain may be present. Complications
can include trouble breathing.
