Influenza

Question 1

What are the 2 types of Influenza?

Answer 1

• Uncomplicated influenza
  
  • influenza presenting with fever, coryza, generalised symptoms and sometimes gastrointestinal symptoms, but without any features of complicated influenza
• Complicated influenza
  
  • ​influenza requiring hospital admission and/or with symptoms and signs of lower respiratory tract infection (hypoxaemia, dyspnoea, lung infiltrate), central nervous system involvement and/or a significant exacerbation of an underlying medical condition

Question 2

What are the three serotypes of Influenza?

Answer 2

• A is the more frequent and the cause of major influenza outbreaks.
• B tends to circulate with A in yearly outbreaks and causes less severe illness.
• C tends to cause a mild or asymptomatic illness akin to the common cold

Question 3

What surface antigens do Influenza A have?

Answer 3

• H: haemagglutinin - facilitates entry of the virus into the host respiratory cell.
• N: neuraminidase - facilitates release of virions from the infected host cells.

Question 4

What is antigenic drift?

Answer 4

• virus undergoes minor mutations to one or both of its surface antigens
• causes seasonal epidemics
• people have only partial immunity from previous infection

Question 5

What is antigenic shift?

Answer 5

• major and sudden changes in the H and N antigens produce a new virus subtype

Question 6

What are the RF for Influenza virus?

Answer 6

• Closed environments - eg, residential homes, schools and prisons.
• Advanced age.
• Pre-existing cardiac or respiratory illness

Question 7

What is the mode of transmission for Influenza?

Answer 7

• Droplet due to coughing/sneezing
• Direct nasal or eye contact with hands carrying the virus

Question 8

What is the incubation period of Influenza?

Answer 8

1-3 days

Question 9

What is the presentation of Influenza?

Answer 9

• Anorexia.
• Malaise.
• Headache (retro-orbital).
• Fever.
• Myalgia.
• Non-productive cough and sore throat

Question 10

How long would most of the influenza sx last?

Answer 10

• 3-5 days

Question 11

How long would the cough, tiredness and malaise last?

Answer 11

1-2 weeks

Question 12

What are the atypical sx of Influenza in children?

Answer 12

Children

• haematemesis
• photophobia
• chest pain
• epistaxis
• croup
• apnoea
• rigors

Question 13

What are the atypical sx of Influenza in neonates?

Answer 13

• lethargy
• poor feeding
• apnoea or fever
• pneumonia
• otitis media

Question 14

What are the differential diagnosis of Influenza?

Answer 14

• Common cold/upper respiratory tract infection.
• Pharyngitis
• Meningitis.
• Bacterial or viral lower respiratory tract infection, including pneumonia.
• Malaria or dengue fever in returning travellers.
• Infectious mononucleosis.
• Cytomegalovirus.
• Acute HIV seroconversion illness

Question 15

What other two important differentials should you consider in pregnant pts c Influenza?

Answer 15

• PE
• pre-eclampsia

Question 16

What Ix would you order for Influenza?

Answer 16

Clinically diagnosed

• viral culture of nasopharyngeal swabs/aspirates.
• Immunofluorescence of nasopharyngeal swabs/aspirates.
• Acute and convalescent sera, 10-14 days apart.
• Polymerase chain reaction.
• Rapid bedside antigen tests

Question 17

How would you Mx Influenza?

Answer 17

• If healthy - self mx
• Pharma options
  
  • Oseltamivir - given within 48 hours of exposure
  • zanamivir - given within 36 hours of exposure

Question 18

What are the Cx of Influenza?

Answer 18

• Acute bronchitis
• Secondary bacterial pneumonia (especially Staphylococcus aureus).
• Primary viral pneumonia.
• Exacerbations of asthma and COPD.
• Sinusitis
• Febrile convulsions.
• Otitis media.
• Heart failure.
• Myocarditis
• Reye’s syndrome.
• Guillain-Barré syndrome.
• Transverse myelitis.
• Encephalitis.

Question 19

What is influenza during pregnancy associated with?

Answer 19

• perinatal mortality
• prematurity
• smaller neonatal size
• lower birth weight