Influenza Flashcards
When does seasonal influenza occur?
During the winter months (December-February in northern hemisphere)
What type of virus is influenza?
RNA virus
What are the three groups of influenza and what species does each affect?
Influenza A- birds and mammals
Influenza B and C- humans exclusively
What are the implications of antigenic drift with influenza?
Occurs within the virus over time and results in genetic variation
Implications- immune system won’t respond as well and issues with vaccinations cause worse than normal epidemics
What is antigenic shift and what are the implications of it?
Abrupt major change in the virus
Allows flu strains to jump species
Involves two or more strains combining to form a new subtype
New antigenic properties so population at risk and pandemics can occur
How does pandemic flu vary from seasonal flu?
Seasonal flu occurs every winter, pandemic flu occurs sporadically
Seasonal flu affects 10-15% of the population, pandemic flu affects 25%+ of the population
Seasonal flu is not usually life threatening, but pandemic flu can be
What properties are required for a pandemic to occur?
Human pathogenicity
Antigenic shift (susceptible population)
Efficient person-person transmission
What are the clinical features of influenza?
Incubation period of 2-4 days
Abrupt fever up to 41°C which lasts 3 days
Plus 2 or more of: Cough, myalgia, headache, malaise.
Predominance of systemic symptoms
Less common symptoms: Nausea, vomiting, diarrhoea
What are the characteristics of influenza-like illness?
Fever >38 degrees
Cough
Onset within last ten days
When does influenza-like illness change names and what is it called?
When admission to hospital is required it is referred to as severe acute respiratory infection
What are the symptoms of swine flu?
Main symptoms: Sudden fever Sudden cough Other symptoms: Tiredness Chills Headache Sore throat Runny nose Sneezing Diarrhoea Loss of appetite Aching muscles Joint/limb pain
How can influenza be transmitted?
Airborne- only direct person-person
Contact- direct or indirect
Virus can survive for 24-48 hrs on non-porous surface or 8-12 hrs on porous surface
What are the risk factors for complicated influenza?
Neurological, hepatic, renal, pulmonary and chronic cardiac disease
Diabetes mellitus
Severe immunosuppression
Age over 65 years
Pregnancy (including up to two weeks post partum)
Children under 6 months of age
Morbid obesity (BMI ≥40)
What are the common complications of influenza?
Acute bronchitis
Secondary bacterial pneumonia
What are the less common complications of influenza?
Primary viral pneumonia Myocarditis Pericarditis Transverse myelitis Myositis/myoglobinuria
What are the symptoms of encephalitis lethargica?
Fever Headache External opthalmoplegia Lethargy Sleep reversal
What investigations can be done for encephalitis lethargica?
Viral nose and throat swabs Chest x-ray Blood culture Pulse oximetry Respiratory rate Blood tests- U&Es, FBC, CRP
What antimicrobials should be given for influenza?
Antiviral therapy started ASAP- ideally within 48hrs of onset of symptoms
First line treatment is oseltamivir or zanamivir
If pregnant- oseltamivir
Immunocompromised adults vary
When is a patient with influenza deemed non-infectious?
24hrs after last flu symptoms or when antiviral therapy is completed, whichever is longer
What protective measures for healthcare staff should be used in influenza?
Surgical face mask
Plastic apron
Gloves
Hand washing
