Influenza Flashcards
Seasonal influenza typically occurs in the winter months.
Which months are these in the north and south hemispheres?
North- Dec-Feb
South- Jun-Aug
Is the influenza virus a DNA or RNA virus?
RNA virus
There are three types of influenza- A, B, C.
Which type(s) affect humans?
B and C
->A affects birds and mammals
The influenza virus is an envelope virus meaning the genetic information is enclosed in a peptide envelope.
Name two types of antigens found in the influenza envelope.
Haemagglutinin (H)
Neuraminidase (N)
-> there are 18 different H antigens and 11 different N antigens and the combination of these results in different types of flu
What does Haemagglutinin do?
Facilitates viral attachment and entry to the host cell
What does Neuraminidase do?
Enables new virion to be released from the host cell
What is antigenic drift?
Mechanism of genetic variation within the virus itself which occurs continually over time with small, continuous changes
What is antigenic shift?
Abrupt major change in the virus resulting in new H/N combinations
Therefore, what is the difference between antigenic shift and antigenic drift?
Antigenic drift- small changes over time
Antigenic shift- sudden big change
->think, if something drifts, it moves slowly compared to something shifting
Which genetic change enables a flu strain to jump from one animal species to another?
Antigenic shift
->this process involves two or more different strains combining to form a new subtype e.g. avian flu went from birds to a pig, where a new subtype was made, which then infected humans
What is the difference between seasonal flu and pandemic flu?
Seasonal- occurs every winter, 10-15% of population affected, usually unpleasant but not life-threatening
Pandemic flu- occurs sporadically, 25%+ population affected, more serious and more complications
What are the three requirements for a pandemic?
Human pathogenicity
‘New’ virus via antigenic shift so susceptible population
Efficient person-person transmission
How is Avian flu spread to humans?
Contact with infected birds, either dead or alive
What is the usual incubation period of influenza?
2-4 days
What is usually the first symptom of influezna?
Abrupt fever which lasts approx 3 days
What are the other symptoms of influenza?
Fever plus 2 or more of;
cough, myalgia, headache, malaise
What is the usual route of transmission for influenza?
Usually airborne/contact
How long can a virus survive on non-porous surfaces e.g. tables, door handles etc?
24-48hrs
How long can a virus survive on porous surfaces e.g. tissue etc?
8-12hrs
Lis some of the high risk groups of influenza complications.
Neurological/hepatic/renal/pulmonary/cardiac disease
Diabetes
Immunosuppression
Young or old
Pregnancy
Morbid obesity
What are some of the common respiratory complications of influenza?
Acute bronchitis
Secondary bacterial pneumonia
Primary viral pneumonia
Rapid respiratory failure
Give an example of a cardiac complication of influenza.
Myocarditis
Pericarditis
Give some examples of a CNS complication of influenza.
Guillain-Barre
Myositis
Mygobolinuria
What is used in the investigations of influenza?
Throat swabs
CXR- signs of pneumonia
Blood culture
Pulse oximetry
RR
Bloods
If SpO2 <92, what needs done?
ABG and oxygen
What can be used to classify the severity of pneumonia?
CURB-65
RECAP- CURB-65?
Confusion
Urea >7mmol/L
RR >30
BP diastolic <60 or systolic <90
>65yrs
What are some of the antiviral therapies which can be used for influenza?
Oseltamivir- oral
Zanamivir- oral or IV
When is treatment required in influenza?
Complicated influenza
Severely immunosuppressed
What is the first line treatment for influenza in pregnancy?
Same, Oseltamivir is first line
When does an individual with influenza become non-infectious?
24hrs after last flu symptoms
Or when antiviral therapy is completed
Why does the flu vaccine change every year?
Prepared based on which viruses considered to be more likely in the forthcoming winter
