Influenza: Everything You Need to Know This Flu Season
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Updated 08 Mar 2024
In 2023, there have already been over 40,000 influenza infections - with more than 8,000 of these cases being diagnosed in a single fortnight (DoHaAC 2023).
So, how can you best protect yourself this flu season?
What is Influenza?
Influenza (known colloquially as ‘the flu’) is a highly contagious, viral respiratory infection (Mayo Clinic 2022).
Influenza infection in humans is most commonly caused by either type A or type B influenza viruses, and there are many sub-types and strains within each of these categories (NSW Health 2023).
Due to being highly transmissible, influenza often causes seasonal, widespread illness. In Australia, flu season typically lasts from April until September (Better Health Channel 2023).
On average, there are approximately 5,100 hospitalisations and 100 deaths caused by influenza every year in Australia (AIH 2023).
The symptoms of influenza can range from mild to serious illness with potentially life-threatening complications such as pneumonia, and can even result in death - even in people who are otherwise healthy (Better Health Channel 2023; AIH 2023).
Influenza is a vaccine-preventable illness (NSW Health 2023).
What Causes Influenza?
Influenza is spread through the respiratory fluids (from coughs and sneezes) of people who are infected with an influenza virus (Better Health Channel 2023).
It can be transmitted by:
Breathing in respiratory droplets after an infected person has coughed or sneezed
Making direct contact with fluid from an infected person’s coughs or sneezes
Touching a surface that has been contaminated by respiratory fluids containing an influenza virus, then touching the eyes, nose or mouth - thus allowing the virus to enter the body.
(Healthdirect 2022)
People with influenza may be infectious from 24 hours prior to the onset of symptoms until one week after the onset of symptoms (although children and immunocompromised people might be infectious for longer) (Queensland Health 2023).
Why are Influenza Cases Increasing?
In 2020, there were 21,266 notified cases of influenza in Australia and 37 deaths (DoHaAC 2020), and in 2021, just 598 cases and no recorded deaths at all (DoHaAC 2021).
Yet, in 2022, there were 225,000 cases of influenza - almost double the five year average (DoHaAC 2022).
The dramatic reduction in influenza cases during 2020 and 2021 can be largely attributed to the public health measures taken in response to the COVID-19 pandemic, which indirectly reduced influenza transmission (AIHW 2021). These measures included:
Face masks
Stay at home orders
Handwashing and sanitising
Closures of schools and workplaces
Restricted travel
Physical distancing
Domestic and international border closures.
(Sonic HealthPlus 2021)
However, most of these restrictions that were put into place have now been rescinded, increasing people’s contact with one another and, consequently, the likelihood of spreading influenza (and COVID-19) within the community.
Symptoms of Influenza
Influenza often has a rapid onset of symptoms, which may include:
Running nose
Sneezing
Cough
Sore throat
Fever and chills
Fatigue and weakness
Reduced appetite
Pain behind the eyes
Headache
Body aches
Vomiting and diarrhoea (more commonly in children).
(Better Health Channel 2023; AIH 2023)
The typical timeline of symptoms is:
Day 1-3
Fever
Headache
Muscle pain and weakness
Dry cough
Sore throat
(Sometimes) stuffy nose
Day 4
Subsiding fever and muscle aches
Hoarse, dry or sore throat
Cough
(Possibly) mild chest discomfort
Tiredness or feeling flat
Day 8
Subsiding symptoms, although cough and fatigue might persist for up to several weeks
(Better Health Channel 2023)
Complications of Influenza
In some cases, influenza can cause potentially severe complications, including:
Pneumonia (primary viral and secondary bacterial pneumonia) - this is one of the most serious complications and can be life-threatening in older adults and people with chronic illness
Acute bronchitis
Croup
Acute otitis media
Asthma flare-up
Acute respiratory distress syndrome
Cardiac issues (e.g. myocarditis or pericarditis)
Encephalitis and/or encephalopathy
Reye syndrome
Haematological abnormalities.
(AIH 2023; Mayo Clinic 2023)
Risk Factors for Influenza
Those identified as being at increased risk of contracting influenza and/or experiencing severe illness from influenza include:
Older adults aged over 65
Infants aged between 6 months and 5 years
Preterm infants aged under 37 weeks of gestation
Aboriginal and Torres Strait Islander Peoples
Those who have never been exposed to an antigenically-related influenza virus
Those infected with a highly virulent viral strain of influenza
Those with certain chronic illnesses (e.g. Down syndrome, heart or lung disease, renal failure, diabetes, chronic neurologic conditions)
Those who are carers or household contacts of people in high-risk groups
Residents, workers, volunteers and visitors at residential care facilities
Workers in the commercial poultry and pork industry
Those proving essential community services
Travellers
Children aged between 6 months and 10 years who are receiving long-term aspirin therapy.
(AIH 2023)
Diagnosis of Influenza
Influenza can be diagnosed through a polymerase chain reaction (PCR) test wherein in a swab is taken from the nose and/or mouth (NSW Health 2023).
Treatment for Influenza
Mild cases of influenza will typically resolve on their own without treatment (Healthdirect 2022). Patients should be encouraged to rest, drink adequate fluids, take paracetamol to manage pain and fever, and use decongestant medicines to relieve their symptoms (Better Health Channel 2023).
Prescription antiviral medicines (such as oseltamivir) may be considered in patients who are moderately or severely ill or are at higher risk of serious illness from influenza (Immunisation Coalition 2021).
In more serious cases, patients may require admission to hospital (Better Health Channel 2023).
Influenza Vaccination
Vaccination is one of the best ways to prevent influenza (Better Health Channel 2023).
While the vaccine can’t guarantee prevention, it does provide a high level of protection against influenza and reduces the risk of severe illness if infection does occur (Better Health Channel 2023).
The Australian Immunisation Handbook (2023) states that all people aged 6 months and over should receive an influenza vaccine every year. This is because:
The specific influenza virus strains included in the vaccine are different every year, depending on global influenza epidemiology
Protection from the vaccine typically begins to decrease after three to four months.
Note: The influenza vaccine can be co-administered with a COVID-19 vaccine (AIH 2023).
When to Escalate Care
The following signs and symptoms in a person with influenza require Immediate medical attention:
Shortness of breath
Chest pain
Sudden dizziness
Confusion
Severe vomiting
Fever accompanied by a rash
Seizures
Worsening of existing medical conditions
Severe muscle pain or weakness
Blue lips (in children)
Dehydration (in children).
(Better Health Channel 2023; Mayo Clinic 2023)
Conclusion
Despite the low rates of influenza in 2020 and 2021, cases are now back to pre-pandemic numbers. The best way to protect against influenza and reduce the risk of serious illness is via immunisation.