Single-stranded RNA virus and is the most common cause of viral pneumonia in immunocompetent adults

Aetiology

• There are three pathogenic serotypes of influenza: A, B and C, of which A and B are the most common
• Influenza B is associated with localised outbreaks of mild disease, whereas influenza A causes worldwide pandemics

At risk groups

• Every year the vaccine is changed to target multiple strains of influenza that are likely to cause flu; needs to be given yearly to keep the person protected
• It is given free on the NHS people at higher risk of developing flu:
  • Aged 65
  • Young children
  • Pregnant women
  • Chronic health conditions such as asthma, COPD, heart failure and diabetes
  • Healthcare workers and carers

Pathophysiology

• Transmitted through droplets or direct contact with infected respiratory secretions

Clinical features

• Fever
• Cough - initially dry and painful, becomes productive but painless
• Myalgia
• Headache
• Malaise
• Sore throat
• Rhinitis
• Anorexia

Investigations

• Treatment is usually started based on the history, risk factors and clinical presentation