Viral Respiratory Infections - RNA Viruses Flashcards Preview

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Flashcards in Viral Respiratory Infections - RNA Viruses Deck (44):

What family are the influenzaviruses in, and what are its physical characteristics?


Enveloped, negative-sense RNA geneome with 8 segments


What influenza protein is primarily involved in attachment and what does it bind?

Hemagglutinin (HA) - binds sialic acid (blocked via mucins)


How is influenza virus uptaken and envelope fused?

Uptaken by receptor-mediated endocytosis, endosome fuses with viral membrane due to pH drop triggering conformational change in HA


What is the function of the M2 protein?

Ion channel which allows protons to enter the virion interior, facilitating pH drop. This frees the ribonuclear complex (RNP) which is RNA + protein

This was targeted by some anti-influenza drugs, but now resistant


Where does influenza-virus replicate?

In the nucleus -> a rarity for RNA viruses

Similar to how poxviruses are DNA and replicate in cytoplasm


What is the function of transcribing RNPs?

Yields + sense RNA, which can be used to transcribe more RNA or viral genomes


What is the function of M1 protein?

Interacts with nascent RNP's to acquire envelopes by budding thru plasma membrane


What is the function of viral neuraminidase (NA)?

Removes sialic acid from cell surface as well as surrounding mucous decoy receptors. Guarantees the virus will not re-infect a previously infected cell, and thins mucuous


What are the two protein components of HA?

Formed from HA0,

HA1 - Binds sialic acid
HA2 - Contains transmembrane domain and fusion peptide for endosome


How do Oseltamivir and Zamanivir work?

Neuraminidase inhibitors


What are the three most common influenza forms and what is the best protective antibody?

H1N1, H2N2, H3N2

Best protective antibody is anti-hemagglutinin


What is antigenic shift vs antigenic drift?

Shift - large change via genetic reassortment and coinfection of two influenza A viruses - cause pandemics

Drift - minor antigenic changes via point mutations - seasonal flu - cause epidemics


What does a typical season flu vaccine formulation contain in it?


Most likely H1N1 strain (Influenza A)
Most likely H3N2 strain (Influenza A)
Most likely Influenza B


What makes an influenza strain especially virulent?

When it has a broad cell tropism (not trypsin dependent, which is only in lungs), which can cause disease in young adults.

Also causes cytokine storm causing inflammation, and predisposes to nasty bacterial superinfections.


Why is trypsin required for influenza?

It is a part of human cells -> required for cleavage of HA0 into HA1 and HA2


How do influenza viruses suppression antiviral interferon responses?

Via NS1 protein, which blocks interferon-induced RNaseL pathway


What type of viruses are Paramyxoviruses?

negative (-) sense RNA genomes, unsegmented


What are the major viruses of the paramyxovirus subfamily?

Human parainfluenza viruses (HPIV 1-4), Mumps Virus, Measles Virus

(Rubella is a Togavirus)


What are the major viruses of the pneumovirus subfamily? This is a part of the paramyxoviridae family

Respiratory syncytial virus (RSV)
Human Metapneumovirus (MPV)


How common are paramyxovirus infections and how are they spread?

Extremely common, especially in childhood. Spread via direct contact with respiratory secretions, aerosols, and fomites.

Most people will have had HPIV and RSV by age 2.


Are repeated infections of paramyxovirus common?

Yes, they are RNA viruses


What is croup? What clinical finding is associated with it?

Laryngotracheobronchitis - An infection and inflammation of the larynx, trachea, and bronchi, narrowing the airway leading to difficulty breathing (upper airway inflammation)

Associated with "stridor" - characteristic sound on inhalation


What viruses tend to cause croup? Do patients need treatment?

HPIV-1 is the most common cause

Other HPIV's and RSV / MPV can cause it too.

Patient needs rapid medical attention due to respiratory distress


What do the paramyxoviruses typically cause in adults?

Laryngitis and pneumonia


What are all the viral causes of pneumonia?

HPIV's, RSV, hMPV, Influenzavirus, Adenovirus, Coronavirus


What is bronchiolitis, does it happen in adults, and what causes it?

Infection and inflammation of the bronchioles
-> small airways between bronchi and alveolae

Symptoms are dyspnea or cough
Rare in adults, mostly in children under 2, primarily caused by RSV


What is Measles Virus also called, and what are its prodomal symptoms?

Rubeola virus

Remember the 4 C's of the prodrome:
Coplik's spots

okay so its spelled Koplik but whatever


What are Koplik's spots?

Tiny blue-white spots on red buccal mucosa in measles prodrome = pathonomonic


What is the pattern of rash in measles? What type of rash it it?

Begins on face, then spreads to trunk and limbs like Rubella

Can form a confluent rash -> spots will start to blend together into a sheet of red


How are mumps transmitted?

Salivary or respiratory secretions -> less infectious than measles


What are the most common manifestations of mumps? Atypical?

Painful swelling of parotid glands (unilateral or bilateral), ear pain

Orchitis -> more severe, can cause infertility if bilateral
Also meningitis


What is german measles and its genome structure?

Togavirus with enveloped icosahedral virus, single stranded +sense RNA


What are the symptoms of Rubella?

1.Lymph node swelling, especially postauricular and occipital nodes
2. Maculopapular rash starting in head and going down (same as measles)

Arthritis in adult women


How long is the incubation period of M,M, and R?

All about 2-3 weeks


What are the features of congenital rubella syndrome?

Sensorineural deafness, intellectual impairment, jaundice / hepatosplenomegaly, cataracts, blueberry muffin rash, patent ductus arteriosus, CNS infection


How many doses of MMR Vaccine should be given?

1st dose at 12-18 months, 2nd dose at 4-6 years


What is the structure of a coronavirus?

Large ss+RNA genome, with envelope and HELICAL nucleocapsid


What type of infection are coronaviruses generally associated with?

Mild to moderately severe URI


What are two coronaviruses of consequence?

SARS - Severe Acute RS - zoonosis from China, caused pneumonia and acute respiratory distress

MERS - Middle East RS - zoonosis from camels, high case fatality


What is the main distinguishing feature of a cold? What is the most common viral cause?

Usually no or mild fever



What is the structure of picornaviruses?

naked ss+RNA


How are picornaviruses spread and what are two main viral subfamilies?

They infect skin and mucous membranes, and thus spread by saliva, mucous, or feces

1. Coxsackievirus
2. Echovirus


What two major diseases does Coxsackie A virus cause?

1. Hand, Foot, and Mouth Disease
2. Herpangina (mouth blisters and ulcers, especially on soft palate)


What are rare complications of measles?

SSPE - Subacute Sclerosing Pan Encephalitis - from measles reactivation in brain

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