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Infection > Influenza > Flashcards

Influenza Flashcards

1
Q

Describe the structure of the Flu Virus

A

Enveloped orthomyxovirus that contains a negative single stranded RNA genome divides into eight segments

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2
Q

Influenza A infects

A

Mammals

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3
Q

Influenza B an C infect

A

Only humans

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4
Q

State the two different surface proteins present on the Influenza Virus

A

Haemagglutin and Neuraminidase

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5
Q

State the function of Haemaglutin

A

Facilitates viral attachment and entry to the host cell

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6
Q

State the function of neuraminidase

A

Enables new virion to be released from the host cell

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7
Q

Why are annual epidemics of flu possible

A

Due to the antigenic drift meaning that there are a sufficiently large number of individuals without immunity for the virus to circulate and in some years for a epidemics to occur.

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8
Q

What is antigenic drift

A

Small on-going point mutations in the genes coding for the antibody binding-sites

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9
Q

What is antigenic shift

A

Abrupt major change in the virus, resulting in new H/N combinations being made. This is what enables a flu strain to jump from one species to another.

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10
Q

What is the consequence of antigenic shift

A

Pandemics

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11
Q

What is different about a pandemic flu

A

They occur sporadically, affect 25% of the population and are more serious with more complications

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12
Q

State the requirements for a flu virus being pandemic

A

Human pathogenicity, New virus, efficient person-person transmission

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13
Q

State the two strains of avian flu which can effect humans

A

H5N1, H7N9

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14
Q

How is avian flu spread

A

Direct contact with infected birds, dead or alive

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15
Q

State the fatality rate of H5N1

A

60%

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16
Q

State the fatality rate of H7N9

A

36%

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17
Q

State the incubation period of influenza

A

2-4 days

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18
Q

State the symptoms of influenza

A

Abrupt fever which lasts around 3 days, cough, sore throat, rhinorrhoea, myalgia, headache, malaise sometimes nausea, vomiting, diarrhoea

19
Q

How is influenza trasmitted

A

Airborne (large droplets), direct contact or indirect contact

20
Q

Virus shedding for influenza occurs

A

First 4 days of illness

21
Q

How long can the virus survive on non-porous surfaces

A

24-48 hours

22
Q

State the respiratory complications of influenza

A

Acute bronchitis, secondary bacterial pneumonia

23
Q

When does secondary bacterial pneumonia tend to occur

A

4-5 days after the start of the flu

24
Q

In which virus does primary viral pneumonia tend to occur

A

H5N1

25
Q

What are the symptoms of primary virual pneumonia

A

Rapid respiratory failure

26
Q

State the mortality rate of primary viral pneumonia

A

40%

27
Q

State the CVS complications of influenza

A

Myocarditis/pericarditis

28
Q

State the CNS complications of influenza

A

Transverse myelitis, myositis and myoglobinuria

29
Q

State the symptoms of encephalitis Lethargica

A

Fever, headache, external ophthalmoplegia, lethargy, sleep reversal

30
Q

State the link between encephalitis lethargica and influenza

A

Influenza A found in serology of patients

31
Q

State the mortality of encephalitis lethargica

A

25%

32
Q

How is Influenza diagnosed

A

Usually clinical diagnosis, viral nose and throat swabs, chest Xray if concerned about pneumonia, blood culture, respiratory rate, U and E, Creatinine, FBC

33
Q

When should patients have an urgent CXRAY to look for secondary bacterial pneumonia

A

If they have flu symptoms and fever for more than 4 days

34
Q

How can influenza be treated

A

Neuraminidase inhibitors like zanamivir and oseltamivir

35
Q

When should patients with influenza be treated with neuraminidase inhibitors

A

Patients at risk of severe complications

36
Q

When should neuraminidase inhibitors be given to be most effective

A

Within 48 hours of onset

37
Q

State the dose of oseltamivir (tamiflu)

A

75mg every 12hours for 5 days

38
Q

State the common side effects of tamiflu

A

Nausea, vomiting, abdominal pain and diarrhoea. Others include, hallucinations, insomnia and rash

39
Q

State the dose of zanamivir

A

10mg inhaled daily for up to 10 days

40
Q

Which strains are resistant to oseltamavir

A

H1N1

41
Q

When does an immunocompetent adult become non-infectious

A

24 hours after last flu symptoms

42
Q

Where is the seasonal flu vaccine grown

A

Allantoic cavity of chick embryos

43
Q

What does the influenza virus contain

A

2 type A and 1 type B subtype

Infection (24 decks)

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