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Respiratory System- URT Viral Infections by Blue
Respiratory System- URT Viral Infections by Blue
Most common disease of any kind in the entire world is...
the common cold.
Top 3 Viral Causes of the common cold.
1. Rhinovirus (100+ strains)
2. Coronavirus (30+ strains)
3. Adenovirus (51 strains)

*rhinovirus has so many strains, that's why it's the most common cause of the common cold. Protection against one strain doesn't mean you're protected against all strains.
Infection scenario (for rhinovirus primarily)
Acquired nasally...
collected in the turbinates which moves the virus back...and in the adenoid area, the epithelial cells are rich with receptors that are necessary for infection (in all 3 of the viruses)
Once infected, is there a lot of viral damage?
There is not a lot of damage, and not enough to cause any kind of symptom. This is all despite the mass production of the virus.
What causes all the symptoms of the common cold?
The person's response to the virus in the adenoid is what causes the symptoms of a common cold. It's not the virus itself that causes the symptoms.
Can URTI turn into LRTIs?
Yes, Patrick, a significant % of URTI lead to LRTI , esp. in young and elderly : bronchitis, bronchiolitis, pneumonia; either primary viral or secondary bacterial.
Describe rhinovirus
>100 strains.
No cross-protective immunity.
Acid labile (destroyed when swallowed, so stay in resp tract), heat stable.
Optimal growth @ 33 degrees centigrade (confines to URT);
Naked capsid (retains environmental infectivity longer than enveloped)
Dx procedures for the common cold...
rarely done. just base it on the symptoms. however, especially in children, rhinovirus the most frequent reason for misuse of antibiotics (followed by influenza).
Histamine
dilation of blood vessels, nasal congestion &plasma exudate; activation of sneeze and cough reflexes
prostaglandins
mucous gland secretion;
kinins
stimulation of pain nerve fibers (sore throat)
cytokines
headache, fever, chills, shivers, muscle aches
Is the virus spread by coughs?
Not really. You don't get the virus form inhaling someone's cough. It's spread by respiratory droplets. It's more from picking it up on a surface by your hands. Watch to see how many times someone touches his/her face.
What causes the symptoms?
The virus doesn't cause the damage. What causes all the symptoms is massive influx of response cells that release inflammatory mediators that causes the symptoms.
Which diseases etc are exacerbated when you have the common cold?
Complications: sinusitis, otitis media exacerbations of asthma, chronic bronchitis, COPD or cystic fibrosis
Is there such thing as an "immune system booster?"
no.
Winter heating dries the mucus membranes of the nose and makes a person more susceptible to catching a cold. T or F?
False. People in the desert get colds also.
Becoming cold or chilled leads to catching a cold. T or F?
No. It's caused by the virus. The body temp stays the same and that has nothing to do with catching a cold.
Having cold symptoms help you get over a cold, therefore you should not treat a cold (relieve symptoms).T or F?
F. It's a good thing to to treat some of the sxs (like decongestants to dry you up) because it'll make you less infectious. the less mucus you got, the less chance you're going to give it to other people.
You should feed a cold (and starve a fever). Tee or eff?
eff.
You can tell the difference between a viral URTI and a bacterial one by the color of the nasal discharge (clear vs. yellow or greenish). Tee or eff?
eff. The inflammatory cells is what changes the colour of the discharge. The more cells you have, the more colour you're going to see in the nasal discharge.
Can you use a vaccine to treat/prevent colds?
Vaccine not probable due to multiplicity of causative viruses, sub-strains. (rhinovirus attachment site is found in a canyon on the virus surface..not a projection, and the canyon is so small that an antibody molecule can't even fit.
What is responsible for recovery, immunity, and therefore short-lived?
Secretory IgA.
What does a coronavirus look like?
ssRNA, enveloped.
What viral diseases are related to coronavirus?
common cold (~ 30%); No. of strains unknown.

SARS – Severe Acute Respiratory Syndrome (LRT)
1st cases Nov. 2002, China: epidemic “ended” July 2003.
8422 cases, 916 deaths, 29 countries; “atypical” pneumonia.
May have crossed over from wild animals (civet, live markets)
Adenovirus characteristics
ds DNA, naked, icosahedral.

51 human strains (1-51), many others of lower animals.
Where do adenovirus develop infections?
in lymphoid tissues (maintain's infectivity for long periods)
What are the major viral diseases associated with adenovirus?
Significant contribution to upper (common cold) and LOWER respiratory tract diseases (bronchitis, pneumonia) in children.

Acute Respiratory Disease- military recruits

Pharyngoconjunctival fever- Swimming pools. pink eye.

Epidemic keratoconjunctivitis-

Infantile gastroenteritis-
Dx of URTI/LRTI?
not frequent.
-detection of specific IgM, rise in IgG titer;
-isolation of virus from naso-pharyngeal, ocular secretions, stools;
-PCR.
Epidemiology, Immunity
Respiratory diseases in children most common in winter, spring. ARD, keratoconjunctivitis occur in epidemics.

Transmitted both by respiratory aerosols and fecal-oral routes.