Influenza
Everything you need to know about Influenza - symptoms, causes, treatment options available in Australia, and when to see a doctor. Evidence-based medical information.
Overview
Influenza, commonly known as the flu, is a highly contagious viral infection that affects the respiratory system. It is caused by influenza viruses, which are classified into types A, B, C, and D, with types A and B being the most significant in humans. The virus primarily spreads through respiratory droplets when an infected person coughs or sneezes. Once inhaled, the virus targets the epithelial cells of the respiratory tract, leading to the characteristic symptoms of the disease.
The pathophysiology of influenza involves the virus entering the host cells and hijacking the cellular machinery to replicate. This process triggers an immune response characterised by the release of cytokines, which contribute to the systemic symptoms of fever, myalgia, and fatigue. Complications can arise, particularly in vulnerable populations, leading to severe outcomes such as pneumonia, myocarditis, and exacerbations of chronic conditions like asthma and chronic obstructive pulmonary disease (COPD).
In 2024, Australia experienced a significant influenza season, with 365,589 notifications recorded, marking the highest number ever reported to the National Notifiable Diseases Surveillance System (NNDSS) [1]. The Australian Bureau of Statistics (ABS) reported 951 influenza-related deaths during the same period [3]. These figures underscore the importance of understanding and managing influenza effectively.
Statistics and Prevalence in Australia
Influenza activity in Australia during 2024 was notably high, with notifications increasing steadily from April and peaking in early July [1]. This pattern is consistent with previous years, where influenza activity typically rises during the colder months. The impact of influenza on the workforce was significant, with many individuals experiencing symptoms such as fever and cough, necessitating three or more days off work [1].
Symptoms and Clinical Presentation
Influenza presents with a sudden onset of symptoms, including fever, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, and fatigue. In some cases, individuals may experience vomiting and diarrhoea, although these are more common in children than adults. Early symptoms often resemble those of a common cold but tend to be more severe and abrupt in onset.
Advanced presentations can include difficulty breathing, chest pain, dizziness, and confusion, which are considered red flags requiring immediate medical attention. In atypical cases, particularly in the elderly or immunocompromised individuals, the presentation may be less pronounced, with symptoms like confusion or generalised weakness predominating [4].
Causes and Risk Factors
Influenza is caused by infection with the influenza virus, with types A and B being the most prevalent in humans. The virus undergoes frequent genetic changes, leading to new strains that can evade the immune system. This antigenic drift necessitates annual updates to the influenza vaccine to ensure effective protection.
Risk factors for severe influenza include age (young children and the elderly), pregnancy, chronic medical conditions (such as asthma, diabetes, and heart disease), and immunosuppression. Additionally, individuals living in crowded conditions or those with limited access to healthcare are at increased risk of infection and complications [1].
Diagnosis
The diagnosis of influenza in Australia is guided by clinical criteria and laboratory testing. According to the Royal Australian College of General Practitioners (RACGP) and the National Health and Medical Research Council (NHMRC), a clinical diagnosis is often based on the presence of fever, cough, and fatigue, particularly during the influenza season [4]. The ASPREN case definition further refines this by including symptoms such as rigours, myalgia, and recent close contact with an infected individual [4].
Laboratory confirmation is achieved through techniques like reverse transcription-polymerase chain reaction (RT-PCR) or rapid molecular assays. However, routine testing is generally reserved for hospitalised patients or those at high risk of complications [4].
Treatment Options in Australia
Treatment of influenza in Australia involves both pharmacological and non-pharmacological approaches. Antiviral medications, such as oseltamivir and zanamivir, are recommended for individuals at high risk of complications or those with severe disease. These medications are most effective when administered within 48 hours of symptom onset [2].
Supportive care, including rest, hydration, and the use of analgesics and antipyretics, is crucial for symptom management. The Medicare Benefits Schedule and Pharmaceutical Benefits Scheme provide coverage for certain treatments, ensuring accessibility for eligible patients [1].
Living with Influenza
Managing influenza involves not only treating the acute infection but also implementing strategies to prevent future episodes. Patients are encouraged to maintain good hygiene practices, such as regular handwashing and covering their mouth and nose when coughing or sneezing. Vaccination remains the most effective preventive measure, with annual influenza vaccines recommended for all individuals over six months of age [1].
Managing this condition is an ongoing process, but many people learn to live well with proper support and care.
Daily management:
- Follow your treatment plan as prescribed
- Keep track of your symptoms and how you're feeling
- Stay in regular contact with your healthcare team
- Learn about your condition so you can make informed decisions
Building your support network:
- Talk to family and friends about your condition
- Consider joining support groups
- Work with healthcare professionals who understand your needs
- Don't hesitate to ask for help when you need it
Self-care strategies:
- Maintain healthy lifestyle habits where possible
- Manage stress and get adequate rest
- Stay as active as your condition allows
- Focus on activities and relationships that bring you joy
Important: With proper management and support, many people with this condition live full and active lives.
For those living with chronic conditions, regular keeping track and follow-up with healthcare providers are essential to optimise health outcomes.
Patient education on recognising early symptoms and seeking timely medical advice can significantly reduce the risk of complications [1].
Prevention
Preventing influenza involves a combination of vaccination, hygiene practices, and public health measures. The annual influenza vaccine is updated to reflect circulating strains and is recommended for all Australians, particularly those in high-risk groups. Public health campaigns emphasise the importance of vaccination and promote awareness of influenza symptoms and transmission [1].
In addition to vaccination, individuals are advised to practise good respiratory hygiene and avoid close contact with infected individuals. During peak seasons, public health measures, such as social distancing and the use of face masks, may be implemented to reduce transmission rates [1].
Key Takeaways
• Influenza is a medical condition that can be effectively managed with proper diagnosis and treatment from healthcare professionals. • Treatment options are available in Australia through Medicare and PBS, making care accessible and affordable for most people. • Early detection and appropriate management can significantly improve outcomes and quality of life for people with this condition.