23. Respiratory Viruses – Flashcards
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| List some respiratory viruses! |
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| - Influenza A, B - Respiratory syncytial virus (RSV) - Parainfluenza viruses (1-4) - Adenovirus - Rhinovirus |
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| What is the division between the upper and lower respiratory tract? |
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| the larynx |
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| Why was there a significant drop in life expectancy in 1918 in the US and Canada? |
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| There was an influenza pandemic |
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| What are some important characteristics of the influenza virus? |
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| - single stranded - RNA virus - enveloped - segmented genome |
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| Why is it significant that the influenza virus has a segmented genome? |
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| Because if two strains infect a cell, they can swap genes and create a whole new strain |
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| There are really three influenza viruses: _, _ and _ |
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| A, B and C but C tends to be unimportant |
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| When are influenza epidemics most common? |
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| they happen on a yearly basis in the winter |
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| Which flu (Flu A, B or C) is most important and why? |
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| - Because of its pandemic potential and because it is usually more severe |
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| How is influenza typically spread? |
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| - droplets and on soiled hands |
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| What two important proteins are on the surface of the influenza virus? |
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| -Hemagglutinin - Neuraminidase |
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| What dose hemagglutinin do? |
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| Sticks the virus to cell receptors |
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| What does neuraminidase do? |
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| Frees the virus to infect other cells |
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| Explain DRIFTS |
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| - Drifts are small changes/mutations that happen continuously over time as the virus replicates (remember than RNA polymerase is sloppy) - This produces viruses that are different but related so they have similar antigenic properties - So an immune system will typically respond if it is similar - But if it changes enough the immune system will not respond |
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| What is the result of drifted viruses? |
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| They contribute to epidemics and an excess number of deaths in the elderly and frail |
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| Explain what SHIFTS are. |
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| - They are reassortments of avian and human viruses - New viruses emerge with new-to-human proteins on their surfaces |
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| Drifts can occur in what kind of influenza? (as in a, b or c) |
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| A and B |
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| Illustrate antigenic shift using the "swine flu" |
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| - A duck is the avian host - often the virus is in the GI tract and gets picked up by animals such as pigs that get the duck poop on their noses. - the virus replicates! - the pig can recognize/be infected with both bird and human strains b/c it has two different receptors in its up respiratory tract - The two viruses can mix (aka re-assort) and create a new virus which can then be transmitted to a human host |
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| Shifts occur in what kind of influenza? (as in A, B or C) |
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| A |
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| In the twentieth century, the world experience three important influenza pandemics... what years, flu A subtype and common names? |
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| 1918- H1N1 --> Spanish flu 1957 - H2N2 --> Asian flu 1968 - H3N2 --> Hong Kong |
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| Since those three pandemics, the world experienced another in 2009 - name subtype and common name |
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| H1N1 - swine flu |
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| How do you get influenza? |
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| - droplet spread - contaminated fingers/hands - fomites - aerosol (controversial) |
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| Explain the steps involved in the influenza-host interaction |
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| - Influenza virus is inhaled - Hemagglutinin activity glycoproteins on the surface of influenza virus attach to sialic acid on the surface of cells in the upper respiratory mucosa - primary replication occurs in the lungs - cytokines are released |
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| What happens when cytokines are released during the influenza-host interaction? |
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| Cytokines prime surrounding cells by sending out a signal that says something is wrong but over release of cytokines can lead to muscle aches, issues with the heart and other organs. Cytokines are what make you feel like crap with the flu |
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| What is the stomach flu? |
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| it doesn't exist (unless the person is referring to norovirus... but even then apparently that shouldn't be called "The Flu") |
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| What are some lower respiratory tract complications associated with influenza? |
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| - Croup and bronchiolitis (in kids) --> there is a direct viral effect, and kids tend to have narrower respiratory tracts - Primary influenza pneumonia |
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| What are some secondary bacterial infection complications associated with influenza? |
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| - pneumonia - otitis media (remember it is often viral but in this case it's bacterial) |
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| What other complications can you have with influenza? |
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| heart failure |
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| What patients get the most influenza complications/benefit most from vaccines? |
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| - Elderly and children - Chronic respiratory disease - Chronic heart disease - Immunosuppression - Haematological disorders - Chronic renal failure - Diabetes mellitus |
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| Why are pregnant women at greater risk for flu? |
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| They are pulmonary compromised! In pregnant women the fetus tends to press up against the diaphragm And they are immunocompromised |
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| What groups of people (besides pregnant women) are at greater risk in flu pandemics? |
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| - Aboriginal populations (environmental and genetic) - Morbidly obese individuals - Current smokers |
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| What type of vaccine is used for seasonal influenza? |
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| Trivalent! 2 type A and 1 type B |
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| What kind of influenza vaccine are live attenuated? |
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| the nasal spray form - they are more expensive |
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| How efficacious are vaccines for influenza in a) healthy young adults b) elderly c) preventing hospitalization and pneumonia? |
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| a) 60-80% b) 20-30% c) 50-60% |
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| How protective are influenza vaccines? |
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| - They are only good when they match with circulating viruses - they are only good if you get re-vaccinated annually |
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| How do we treat influenza prophylactically? |
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| We use neuraminidase inhibitors - Osteltamivir --> influenza A and B - Zamamivir --> influenza A and B |
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| How is zamamivir administered? |
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| via a cumbersome inhaler |
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| Respiratory Syncytial virus is a ____. |
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| paramyxovitus |
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| What is important about the RSV structure? |
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| it is enveloped |
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| When do RSV epidemics occur? |
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| - In the winter but also sporadic cases occur throughout the year |
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| How is RSV transmitted? |
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| By hand contact (less common: respiratory route) |
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| RSV is responsible for causing ____ in children and the ___ ___ in older kids/adults |
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| bronchiolitis common cold |
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| RSV may be fatal for certain children... which ones? |
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| - Those who have heart and lung disease - those who are premature |
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| Is RSV treatable? |
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| yup |
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| What is Ribavirin used to treat? |
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| It is used to treat severe infections --> RSV - note: it is expensive and requires hospitalization |
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| ___ viruses are second only to RSV in infants and young children |
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| Parainfluenza |
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| Parainluenza virus infections are often limited to which anatomical area? |
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| the nasopharynx |
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| How common is croup with parainfluenza virus? |
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| 2% get it! It's formal name is laryngo-tracheo-bronchitis |
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| What is the classic sign on a x-ray with Croup? |
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| The "steeple" sign - where there is narrowing of the tracheal air column at the larynx and distension of the hypo pharynx |
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| What type of virus is the adenovirus? |
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| it is double stranded and naked (how risque of you adenovirus) DNA virus |
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| How does Adenovirus get transmitted? |
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| - Direct contact or respiratory droplets |
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| Adenovirus produces _-_% of pediatric respiratory infections |
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| 5-10% |
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| What are the clinical syndromes associated with adenovirus? |
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| - Febrile pharyngitis - Lower respiratory infections - Pharyngoconjunctival fever - Conjunctivitis - Diarrhea |
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| What kind of virus is Rhinovirus? |
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| - a picornavirus -it is a positive strand RNA virus |
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| Where do we primarily see rhinovirus? |
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| In upper airway: - common cold and viral sinusitis |
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| On average, how many colds do children have per year? |
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| 2-8 per year! |
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| Who should be most concerned about enterovirus? |
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| - asthmatics, immunocompromised people and children/babies |
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| What type of symptoms are a result of Enterovirus D68? |
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| - mild to severe resp. illness - fever, runny nose, sneezing, cough and body/muscle aches |
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| How common is enterovirus in adults? |
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| It can be seen in adults... 25% of cases in past outbreaks |
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| How do we diagnose respiratory viral infections? |
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| - Clinical syndromes - Time of year - What's going around in the community - Virus isolation - Virus antigen detection (but not with rhinovirus) - Molecular methods (e.g. PCR) - Serology (not common) |
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| How long do otherwise healthy people shed when they have been infected with influenza? What about immunocompromised patients? |
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| 5 to 7 days weeks |
