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9. Infection (Medical Knowledge) > 10 - Influenza > Flashcards

10 - Influenza Flashcards

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USMLE® Step 1 flashcards
1
Q

What family is the Influenza Virus from?

A

Orthomyxoviridae Family:
RNA Virus with an 8 Segment Genome

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2
Q

How many, and what are, main groups of Influenza Virus are there?

A

3:
1. IfA (Mammals and Birds)
2. IfB (Humans)
3. IfC (Humans)

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3
Q

What is the definition of Antigenic Drift?

A

A Mechanism of genetic variation (within the Virus) which occurs continually over time

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4
Q

By what method does Antigenic Drift occur?

A
  1. Small, on-going, point mutations in the genes coding for the antibody-binding sites
  2. May also change the antigenic properties
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5
Q

What is the advantage of Antigenic Drift?

A
  1. Eventually the immune system will not combat the virus as well
    Note - it causes worse than normal epidemics and vaccine mismatch
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6
Q

What is the definition of Antigenic Shift?

A

The process by which 2+ different strains of a Virus combine to for am new sub-type, resulting in new H/N combinations, and reassortment of the Virus’ gene segments

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7
Q

What does Antigenic Shift allow for?

A

The flu strain can jump from one animal species to another

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8
Q

What can an Antigenic Shift lead to?

A

With new antigenic properties, the population at risk is unprotected, this can lead to Pandemics
E.g. An Avian Host and a Human Host both transmit into a Swine Host, and a New Reassorted Virus Subtype is formed

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9
Q

What is the difference between Seasonal Flu, and Pandemic Flu?

A

Seasonal Flu:
1. Occurs every winter
2. Affects 10-15% of the population
3. Usually unpleasant but not life threatenting
Pandemic Flu:
1. Occurs sporadically
2. Affects >25% of the population
3. More serious, more complications

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10
Q

What are the requirements for an infection to be “Pandemic”?

A
  1. Human Pathogenicity
  2. “New” Virus (due to the antigenic shift)
  3. Efficient Person - Person transmission
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11
Q

What are the 2 Surface proteins on Influenza?

A
  1. Haemagglutinin (H)
  2. Neuraminidase (N)
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12
Q

What is the function of the Haemagglutinin (H) Antigen?

A

Facilitates Viral Attachment and Entry to the Host Cell

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13
Q

How many different Haemagglutinin (H) Antigens are there?

A

18 (H1-3 in humans)

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14
Q

What is the function of the Neuraminidase (N) Antigen?

A

Enables the new Virion to be released from the Host Cell

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15
Q

How many different Neuraminidase (N) Antigens are there?

A

11

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16
Q

What are the strains of Avian Flu which affect humans?

A
  1. H5N1
  2. H7N9
17
Q

How does Avian Flu spread to Humans?

A

Through direct contact with infected birds, dead or alive
Note - there is no known transmission by eating properly cooked food/eggs

18
Q

What are the fatality rates of the Avian Flu which can affect humans?

A
  1. H5N1 - 60%
  2. H7N9 - 36%
19
Q

What is the incubation period of Avian Flu?

A

2 - 4 days (range is 1 - 7 days)

20
Q

What are the clinical features of Avian Flu?

A

Abrupt Fever (up to 41 degrees) which lasts for 3 days
Plus 2 or more of:
1. Cough
2. Sore Throat
3. Rhinorrhoea
4. Myalgia
5. Headache
6. Malaise
Note - there is a predominance of systemic symptoms and nausea, vomiting and diarrhoea are less common

21
Q

What are the clinical features of Swine Flu?

A
  1. Abrupt Fever (above 38 degrees) which lasts for 3 days
  2. Sudden Cough
  3. Tiredness / Chills
  4. Headache / Sore Throat / Runny Nose / Sneezing
  5. Diarrhoea or Upset Stomach / Loss of Appetite
  6. Aching Muscles / Limb or Joint Pain
22
Q

How is Swine Flu transmitted?

A
  1. Airborne: Person to Person by large droplets
  2. Direct Contact: Person to Person
  3. Indirect Contact: Person to Fomite to Person)
23
Q

How long does the Virus Survive for:
1. In the host?
2. On a Porous Surface?
3. On a Non-porous Surface?

A
  1. Around 4 Days - longer in children and immunocompromised patients
  2. 8-12 hours
  3. 24-48 hours
24
Q

Which groups of people are at high risk of developing Flu?

A
  1. Chronic Respiratory Disease (especially those on continuous Oral Steroids)
  2. Chronic Heart / Renal / Liver / Neurological Disease
  3. Diabetes Mellitus
  4. Immunosuppression
  5. Morbid Obesity
  6. Pregnancy - especially the last trimester
25
Q

What are common Respiratory problems, associated with the Flu?

A
  1. Acute Bronchitis
  2. Secondary Bacterial Pneumonia
26
Q

What are some un-common problems, associated with the Flu?

A
  1. Primary Viral Pneumonia
  2. Myocarditis / Pericarditis
  3. Transverse Myelitis / Guillian-Barre
  4. Myositis and Myoglobinuria
27
Q

How is the Flu diagnosed / investigated?

A
  1. Clinical Diagnosis (for normal Flu)
  2. Viral Nose / Throat Swabs
  3. Chest X-Ray
  4. Blood Culture
  5. Pulse Oximetry
  6. Respiratory Rate
  7. U&E’s, Creatinine and FBC
  8. CRP
28
Q

In relation to Secondary Bacterial Pneumonia (a common problem associated with Flu), what is the score used to assess Pneumonia?

A

CURB65:
C - Confusion
U - Urea (> 7mmol/L)
R - Respiratory Rate (> 30 breaths per minute)
B - Blood Pressure (Diastolic < 60, Systolic < 90)
65 - >65 years of age

29
Q

What is the common Antiviral Therapy associated with Influenza?

A
  1. Oseltamvir
  2. Zanamivir (dry powder inhaler)
30
Q

What is the treatment of an uncomplicated case of Influenza, in a previously healthy person?

A
  1. No treatment (ideal and most common course)
  2. Oseltamvir (If the physician feels the patient is at serious risk of developing complications)
31
Q

What is the treatment of an uncomplicated case of Influenza, in an at risk (but not severely immunosuppressed) person?

A
  1. No treatment (ideal and most common course)
  2. Oseltamvir (If the physician feels the patient is at serious risk of developing complications)
32
Q

What is the treatment of an uncomplicated case of Influenza, in an at risk (severely immunosuppressed) person?

A
  1. Oseltamvir PO and Clinical follow up within 48 hours
  2. Zanamivir within 36 hours of onset
    Note - Zanamivir is added to those with higher risk of resistant strains
33
Q

What is the treatment of an complicated case of Influenza, in a person who is not severely immunosuppressed?

A

1st Line - Oseltamvir PO / NG
2nd Line - Zanamivir Inh / Neb / I.V.

34
Q

What is the treatment of an complicated case of Influenza, in a person who is severely immunosuppressed?

A

1st Line - Oseltamvir PO / NG
2nd Line - Zanamivir Inh / Neb / I.V.

35
Q

What are some other, less common Antiviral Therapies, associated with Influenza?

A
  1. Peramivir
  2. Favipiravir
36
Q

How long does it take an immunocompetent adult to become non-infectious?

A
  1. 24 hours after the last flu symptom
  2. When antiviral therapy is complete
37
Q

What PPE is required when the Flu is suspected / proven?

A
  1. Surgical Face Mask
  2. Plastic Apron
  3. Gloves
  4. Hand Washing after any examination
38
Q

What do Seasonal Flu Vaccines contain?

A

They are a Trivalent:
1. Contains 2 type A subtype virus
2. Contains 1 type B subtype virus

39
Q

Why do healthcare workers have vaccinations?

A
  1. To protect themselves and their families
  2. To reduce the risk to “at risk” patents
  3. To reduce absence from work during influenza “surge” activity

9. Infection (Medical Knowledge) (29 decks)

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