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Viral Infections of the Respiratory Tract

Know the symptoms, complications, treatments, and etiology of the common cold, croup, hand-foot-and-mouth disease, herpangina, viral bronchiolitis, and viral pneumonia. Be able to discuss the mode of transmission and other diseases associated with the viruses that frequently cause the common cold including: Rhinovirus, Coxsackievirus, Adenovirus, Coronavirus Be able to discuss the basic virology, clinical aspects, treatment, and prevention of viral infections of the respiratory tract including:…
Every time you sneeze how many particles are released?
What % of acute illness of the upper respiratory tract are caused by viruses?

When are they usually presented?

How can viruses and bacterial infection be connected?
The upper respiratory tract-is a few degrees cooler than the lower respiratory tract, viruses which display optimal replication at these temps do not commonly spread to the lower respiratory tract.
What are symptoms of common cold? What is the incidence? What are possible complications? What are possible differential diagnosis?
IF pts present with recurrent symptoms restricted to the upper respiratory tract, then allergies should also be considered in the differential diagnosis.
What are the most common causes of the common cold?
1. Rhinoviruses-half of all colds
2. Non-SARS coronaviruses
3.Other-adenoviruses, parainfluenza, influenza, respiratory syncytial viruses and Coxssackie A viruses.
4. 1/3 of colds possess an unknown etology, but are assumed to be due to virus
Describe the main features of the Rhinoviruses?
Picornavirus family member
+ ssRNA genomes
Major receptor is ICAM-1, a member of the immunoglobulin supergene family

Over 100 different serotypes of rhinovirus circulate in the human population.

Shed in respiratory secretions.Infect the ciliated mucosal epithelial cells, infected cells slough off from the surface of the epithelium.

Transmission through direct contact with nasal secretions, large droplets, and contaminated fomites.

Extremely low inoculum needed for infection.
Incubation period 1-3 days.

Exacerbates asthma in school-aged children
What is the pathology of rhinoviruses?
Rhinoviruses infect the ciliated mucosal epithelial cells. Infected cell slough off from the surface of the epithelium.

Early infection the increase in nasal secretion is mainly due to the increase in vascular permeability.

Latear nsasl secretions are due to the glandular secretions such as lactoferrin, lysozyme and immunoglobuin A.

Psychological stress seems to increase susceptibility to infection.
What is the treatment and prevention of the Rhinovirus?
Immune response to rhinovirus infection can be long lasting in a serotype specific manner. But, 100 + serotypes!

No vaccine available.

Treatment regimens aimed to alleviate symptoms, e.g, antihistamines, decongestants.
Antibiotics should NOT be given EXCEPT if there is another bacterial infection. Antibiotics only given in the case of bacterial superinfections.
What are features of Non-SARS coronaviruses
+ ssRNA genome
Replicate in the epithelial cells of the respiratory tract.
Known receptors include metalloproteases such as human amino peptidase and angiotensin converting enzyme 2, and 9-O acetylated neuraminic acid.

Optimal temperature for replication is 33- 35 degrees C (upper respiratory tract.)

Transmission occurs through large droplets.
Incubation period approximately 3 days.

Outbreaks common in the spring and winter months.

Infections are most common in infants and children.
What is the treatment and prevention for the Non-SARS Coronavirus?
Like rhinoviruses, the treatment for Non-SARS coronavirus infections is aimed to alleviate symptoms.

No vaccine available.

Reinfection can occur despite circulating antibodies-no long lasting immunity

Duration of the illness is about 1 day longer than the rhinovirus.
What are main features of the Adenoviruses?
How are Adenoviruses transmitted? Where do they replicate? What are most common serotypes of that cause disease?
Over 50 different serotypes of adenovirus.

Most common respiratory disease causing serotypes are 1, 2, and 5.

Infections most prevalent in children under 5 yrs

Transmission: Oral, droplet inhalation, conjunctiva.
Replicates in respiratory epithelial cells causing tissue damage.

May enter lymphoid tissues following acute infection.

Individuals can shed virus for up to 18 months following infection without clinical apparent disease.
What other illness can be caused by Adenoviruses?
What is the treatment and prevention for the Adenovirus?
Treatment are aimed at reducing symptoms.

Immunity is long-lived, but serotype specific.

Live oral vaccine to serotypes 4 and 7 for military recruits.
What are some features of the Coxsackieviruses? How is it treated?
Their ability to survive low pH makes them able to Transmit through the fecal-oral route.-probably one of the reasons we see it with places of young children.

No vaccine available.

Recovery generally occurs in a couple of weeks without treatment.
What the symptoms of the coxackievirus Herpangina, the incidence and complications?
What are the symptoms of Hand foot and mouth Disease Coxsackie virus? What is the incidence?
What are the etiology of common cold viruses?
What is CROUP?
AKA laryngotracheobronchitis

Hypoxia occurs in about 80% of children with croup severe enough to require hospitalization.
What is the treatment goal in Croup?
What is the number one cause of Croup?
What is the parainfluenza virus ?
Has the fusion protein-needs to be cleaved by celllular proteolytic enzymes in order to become activated and mediated fusion of viral and cellular membranes
What is the transmission like for parainfluenza? what is the incubation period? what is the pathogeneiss?
In children, viral shedding can shed virus as early as 6 days prior to the onset of symptoms. Therefore, children are often a major vector of this virus spread.

2nd most frequen cause of pneumonia and bronchiolits in children.

immune repsonses to the hemagglutininneuraminidase and F virion surface glycoproteins correlate with protection against infection. Ex, infants taht recieve higher maternal antidoies to this virus are better protected against lower repiratory tract disesase cuased by the virus than those recive a low level of antibody.
What are common symptoms of the influenza virus? What is the incidence? What is the incubation period?
Causes lower respiratory most commonly
Who are people at high risk for complications due the influenza virus?
What is pneumonia? What are some symptoms?
Common caues of viral pneumonia in children include Respiratory syncytial virus (RSV) and parainfluenza virus-espeically type 3.

Measles virus pneumonia was common complication prior to the vacinne.
There are two type of pneumonia associated with influenza. Describe primary influenza virus pneumonia? Symptoms, incidence etc...
This type is less commonly seen.
Describe the bacterial influenza-associated pneumonia...
What causes influenza?
Hemmaglutanin-agglutinates RBC, not related to pathogenesis but important for diagnosis.

Our bodies recognize viral H and N proteins.
How does the influenza virus change to evade the immune system? Two main ways?
Describe Reassortment.
Where can reassortment occur? Can it occur in other animals? How?
avian influenza viruses do not efficiently infect human cells and vice versa. Pigs are thought to be capable of acting as a mixing vessel for influenza viruses of birds and humans.

Therefore humans, swine, and birds living in close proximity to one another can present a problem.
What are the most frequent causes of pneumonia in pts in the out patient, hospital or intensive care units?
Most frequent cause of viral pneumonia in healthy adults is influenza virus
How would you treat viral pneumonia
dependent upon severity

oxygen administration may be critical especially where hypoxia is present

antivirals and or antibiotics treatment may be warranted depending on the etiological agent.
Describe the influenza virus
member of the orthomyxovirus family

enveloped virus

-ssRNA genome that is separated into 7-8 segments

enveloped is covered with Hemagglutinin and Neuramindidase glycoprotein spikes

requires a RNA dependent RNA polymersease to be packaged within their genome

three serotypes of influenza A, B and C

C-generally cause mild respiratory illness, capable of infectin both humans and swine

B-casues mild respiratory disease, however more severe disease has been occasionally observed, no animal reservoir, more common than influenza C

A-most dangerous of the clinically, cause severe respiratory disease that can include life threatening pneumonia

8 segments in their genomes

infects humans, pigs, birds, horses and marine mammals
Describe influenza virus A, B and C
The only type of flu that has been shown to undergo antigenic shift is influenza type A
Describe the flu virus as a pandemic.
pandemics of the influenza virus are characterized by increase in illness rates in all age groups and are usually accompanied by increased mortality rate.

Deaths occur most commonly in elderly, exception to this is the 1918 pandemic that caused unexplained increased of mortality in the 20-40 yr age group.
How do you go about naming influenza viruses?
How do you go about treating influenza with antiviral starting with a mild or uncomplicated illness.
What are some examples of influenza antivrials that block ion channels?
Amantadine-H1N1 and H3N2 have been found to be resistance. If you are usually resistant Amantadine most likely to resistant to Rimantadine, not the case for the other class.
What are some examples of influenza antivirals that inhibit neuramidnidase?
Not a lot of resistance to these yet.
Explain the inactivated and attenuated vaccine for the flu virus.
inactivated-approved for the widest age range

attenuated-cold adapted-can grow well at cold temperature, it can replicate in the upper respiratory tract, enough to invoke an immune response, but it cannot grow in the lower respiratory tract, cannot cause disease.

All of these are initially grown in eggs, you shine the light, and it lights up, that mean the virus is growing.
When should the flu vaccine be distributed and administrated?
What is chemoprophylaxis? How is it used in prevention for the flu? Who might need this?
You want to protect them for the 2 months until the flu vaccine kicks in.

Each year the demand for this changes, it becomes in high demand when there is a poor match between the vaccine and the current circulating virus.
Describe the 2009 Novel Influenza A H1N1 virus.
Jan-March see a peak due to influenza like illness. This is typical.

The Red line is 2008-2009, you see multiple big peaks in April also.
Explain the resassortment of H1N1
Mixture of a lot of different viruses.
H1N1 influenza compared to seasonal flu?
spread widely, but did not cause much more severity than the seasonal flu virus.
What is SARS? Ifs family and viral characteristics
What is the clinical presentation of SARS, How is it transmitted? What is the incubation period?
First time a member of this family was found to cause serious problems.
What is the incidence of the SARS virus?
How was the SARS virus controlled which contributed to the success of limiting it.
infection control measures-isolation techniques, health care workers were wearing masks, they had isolation techniques.

In Japan, in the airport they would look for people with fever...and then they would test them, and then isolate them. People were caught at an early phase before they could infect other people.
What is bronchiolitis?
What is the RSV?
How is RSV transmitted, what is the incubation, and incidence?
RSV Season varies by region
How does aerosolized ribavirin treatment work? What is it indicated for?
How do we prevent RSV? Who is it indicated for? What are examples of drugs?
Different from a vaccine-you only give once or a course of it, causing a long lasting immune response, in this case, we are giving antibodies to the pt, which only gives a short length of immunity.
Avain influenza
bird to human NOT human to human transmission
immunocompromised individuals
Measles and Varicella Zoster virus
usually associated with distinct skin lesions