Influenza (Flu)

Influenza (or the ‘flu’) is a common and contagious viral infection affecting the nose, throat and lungs. It is spread from person to person by inhaling airborne droplets containing the virus, such as through talking, coughing or sneezing.

The flu can sometimes be confused with the common cold, but symptoms of the flu are normally much worse and include fever, fatigue and muscle aches, and the virus may cause serious illness in some people. The risk of complications is highest in young children, elderly adults, pregnant people, and those with underlying health conditions (e.g. asthma, COPD (chronic obstructive pulmonary disease), cardiovascular disease, and diabetes).

Although the flu can occur all year round, the flu season typically occurs in New Zealand between May and September each year.

A person can be infectious for about a day before symptoms appear.

The flu virus is easily spread from person to person by inhaling droplets in the air containing the virus, through coughing, sneezing, talking, or direct contact with an infected person (whether they have symptoms or not).

The flu can also be spread by contact with surfaces that have been contaminated with the virus, usually from sneezing.

Healthy adults with the flu are usually infectious for up to 7 days, and children for up to 14 days.

Influenza is caused by different strains or types of influenza viruses, which can change from year to year.

Your best protection against catching the flu is to get the annual flu vaccine. Each year the vaccine is adjusted to match the latest strains of the disease.

Symptoms usually appear suddenly, one to four days after exposure to the virus, and may include a combination of:

• muscle or body aches
• fever or feeling feverish (a temperature of 38 °C or higher)
• chills
• sore throat
• headache
• cough
• severe fatigue (tiredness)
• diarrhoea and vomiting (particularly in children)

The fever and body aches can last for 3 to 5 days, while the cough and fatigue may last for two weeks or more.

As symptoms of the flu are similar to the COVID-19 virus, people are advised to test for COVID-19 and take appropriate precautions.

The risk of complications is highest in:

• young children
• elderly adults
• pregnant people
• people with underlying medical conditions.

Complications include pneumonia (from the influenza virus itself, or due to a secondary bacterial infection), otitis media (middle ear infection), a worsening of pre-existing respiratory or cardiovascular (heart) conditions, febrile seizures in young children, and inflammation of the brain.

Most influenza diagnoses are based on the person’s symptoms.

A healthcare practitioner may do a physical examination to check for signs and symptoms of the flu.

People can purchase rapid antigen testing (RAT) tests from pharmacies, which are able to test for influenza A or B, RSV (respiratory syncytial virus) and COVID-19 infection.

For most people, symptoms of the flu will resolve on their own in 7 to 14 days.

There is no specific treatment and most cases can be managed at home with rest, fluids (to prevent dehydration), and over-the-counter medicines from your pharmacy for pain and fever, nasal congestion, and throat lozenges or throat sprays.

Always check with your pharmacist before buying any cough and cold medication if you are currently taking other prescription or over-the counter medicines, or if you have other health conditions.

As influenza is a viral infection, it cannot be treated with standard antibiotics, but there are some antiviral medications that are recommended for people who are at high risk of complications, such as pregnant women and people who are immunosuppressed.

Seek immediate medical advice if you are pregnant and think that you may have the flu, or if you or a family member have:

• a high fever that does not come down, especially if you are pregnant
• chills or severe shaking
• a rash
• difficulty breathing or chest pain
• purple or bluish colour of your lips, skin, fingers or toes
• severe headache or stiff neck
• dislike of bright lights
• seizures or convulsions
• signs of dehydration, such as dizziness when standing, or difficulty passing urine regularly

If a person you take care of is less responsive than normal, is unusually quiet, or is confused, then seek medical help from your healthcare provider urgently.

Along with basic hygiene principles (regular hand washing and drying or using a hand sanitiser, sneezing or coughing into a disposable tissue or your elbow, disposal of used tissues, and not sharing eating or drinking utensils), having the annual flu vaccine is the best way to protect yourself from getting the flu.

The flu vaccine is free for some people at higher risk of getting very sick, including:

• pregnant women
• people aged 65 years and over
• people aged 6 months and over who have a long term medical condition like asthma, COPD, or a heart condition
• children aged 4 years and under who have been hospitalised for a respiratory illness, or who have a history of significant respiratory illness