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Microbiology > Orthomyxoviridae And Paramyxoviridae > Flashcards

Orthomyxoviridae And Paramyxoviridae Flashcards

0
Q

What are the viruses that are included in Paramyxoviridae?

A
  1. Parainfluenza virus
  2. RSV
  3. Metapneumovirus
  4. Mumps virus
  5. Measles (rubeola) virus
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1
Q

What is the virus that is included in orthomyxoviridae?

A

Influenza virus

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2
Q

What percentage of the entire world population gets infected with the influenza virus every year?

A

20%.

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3
Q

Describe briefly the structure of orthomyxoviridae.

A
  1. Spherical virions
  2. At the center lie 8 segments of negativ (-) stranded RNA put together with a protein (nucleocapsid protein - NP) into a helical symmetry.
  3. Surrounding the nucleocapsid lies an outer membrane studded with long glycoprotein spikes.
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4
Q

What are the two distinct types of glycoproteins?

A
  1. One with Hemagglutinin Activity (HA)

2. One with Neuraminidase Activity (NA)

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5
Q

What are the M proteins?

A

Anchoring the bases of these glycoprotein spikes on the inside of the viral lipid bilayer are membrane proteins. (M proteins)

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6
Q

What is the role of hemagglutinin?

A
  1. Can attach to sialic acid receptors - RBCs.
  2. Also on upper respiratory tract cell membranes.
  3. So hemagglutinin is essential for adsorption.
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7
Q

What will antibodies against hemagglutinin cause?

A

They will block the binding of the virus and prevent infection.

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8
Q

What is the action of neuraminidase?

A

Neuraminic acid is an important component of mucin, a substance overlying mucosal epithelial cells.
This enzyme cleaves neuraminic acid and disrupts the mucin barrier, exposing the sialic acid binding sites beneath.

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9
Q

How many types of influenza virus exist?

A

Three - A,B,C

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10
Q

What is the antigenic drift?

A

During viral replication mutations can occur in the HA or NA, leading to changes to the antigenic nature of these glycoproteins. The changes are small.

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11
Q

What occurs with antigenic shift?

A

Complete change of the HA and NA. This can only occur with influenza type A, because the mechanism involves the trading of RNA segments between animal and human strains.

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12
Q

What are the main complications of influenza?

A
  1. Pneumonia in the immunocompromised.
  2. Also lowers the host defenses against many bacteria - S.aureus, S.pneumoniae.
  3. New fever or failure to improve means DANGER.
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13
Q

What are the 4 broad categories of diagnostic tests for influenza?

A
  1. Virus isolation
  2. Detection of viral proteins
  3. Detection of viral nucleic acid (RNA)
  4. Serological diagnosis: 4-fold increase in specific antibody levels over 2 weeks.
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14
Q

The structure of paramyxoviridae is very similar to that of the orthomyxoviridae. What are the differences?

A
  1. The negative stranded RNA is in a single strand, not segmented.
  2. HA and NA are a part of the same glycoprotein spike, not 2 different spikes.
  3. They possess a fusion (F) protein that causes the infected host cells to fuse together into multinucleated giant cells.
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15
Q

What are the 5 paramyxoviridae that cause human disease?

A
  1. Parainfluenza virus
  2. RSV
  3. Metapneumovirus
  4. Mumps virus
  5. Measles virus
16
Q

What is the big picture of Paramyxoviridae?

A
  1. Think lungs
  2. Think kids
  3. Think viremia
17
Q

What does the parainfluenza virus cause?

A
  1. Cold symptoms such as rhinitis, pharyngitis, sinus congestion.
  2. Bronchitis and flu-like illness.
  3. Children, elderly, immunocompromised suffer from lower respiratory tract infections (pneumonia).
18
Q

What is the Croup?

A

A parainfluenza infection of the larynx and upper respiratory structures (laryngotracheobronchitis) that occurs in children.
Swelling of these structures produces airway narrowing.

19
Q

Why RSV is called RSV?

A

RSV is so-named because it causes respiratory infections and contains an F-protein that causes formation of multinucleated giant cells (syncytial cells).

20
Q

What is the main difference of RSV from the rest of its kin?

A

RSV lacks both the HA and NA glycoproteins.

21
Q

What is the number one cause of pneumonia in young children, especially in infants less than 6 months of age?

A

RSV

22
Q

When was metapneumovirus first isolated?

A

In 2001.

23
Q

What is the 2nd MC etiology of lower respiratory infections in young children?

A

Metapneumovirus.

24
Q

What can metapneumovirus cause?

A
  1. Bronchiolitis (50%)
  2. Croup (20%)
  3. Pneumonia (<10%)
25
Q

Where does mumps virus replicate?

A

In the upper respiratory tract and in regional lymph nodes - spreads via the blood to distant organs.

26
Q

What are the organs particularly involved in mumps?

A

Infection can occur in many organs but the most frequently involved is the parotid gland.

27
Q

What percentage of infected by mumps males who have reached puberty can develop orchitis?

A

About 25%.

28
Q

What else can mumps virus cause?

A
  1. Infertility (rare)
  2. Meningitis (more common + more severe)
  3. Encephalitis
29
Q

How many antigenic types of mumps virus exist?

A

There is only one type.

A live attenuated viral vaccine is a part of the trivalent measles-mumps-rubella (MMR) vaccine.

30
Q

How is measles virus transmitted?

A

It is highly contagious and spreads through nasopharyngeal secretions by air or by direct contact.

31
Q

Where does the virus multiply?

A

In the respiratory mucous membranes and in the conjunctival membranes.

32
Q

How long does the incubation of measles virus last?

A

2 weeks prior to the development of the rash.

33
Q

What are the symptoms of the prodrome phase of measles virus?

A
  1. Conjunctivitis
  2. Swelling of the eyelids
  3. Photophobia
  4. High fevers to 105F
  5. Hacking cough
  6. Rhinitis
  7. Malaise
34
Q

What are the Koplik’s spots?

A

A day or 2 before the rash, the patient develops small red-based lesions with blue-white centers in the mouth.
Think of a cop licking a red-white-blue lollipop.

35
Q

Describe the measles rash.

A
  1. Red, flat to slightly bumpy (maculopapular).

2. It spreads out from the forehead to the face, neck, and torso, and hits the feet by the third day.

36
Q

Mention some complications of measles.

A
  1. Pneumonia
  2. Eye damage
  3. Heart involvement (myocarditis)
  4. Encephalitis - most feared - 10% who develop this will die.
37
Q

What is subacute sclerosing encephalitis?

A

A slow form of encephalitis caused by measles virus.

Microbiology (46 decks)

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