Influenza

Influenza (flu) is a contagious virus that spreads easily from person to person and infects the nose, throat and lungs. Influenza viruses spread easily from person to person through the air in droplets when someone with the flu coughs, sneezes or speaks. Virus droplets can be inhaled or picked up from an object like a door handle or computer and enter your body through the mucus membranes in your nose.

Influenza symptoms – is it a cold or the flu?

The first flu symptoms may appear like a common cold including a runny nose, sneezing and a sore throat. While a cold develops slowly, the flu is fast and includes fevers and aches. Flu symptoms last about a week and include

• Fever
• Cough
• Sore throat
• Headaches
• Runny nose
• Aching muscles or body
• Shortness of breath
• Tiredness and weakness
• Vomiting and diarrhea.

While the fever and aching muscles usually stop within a week, other flu symptoms like a cough and tiredness may continue for more than a week.

Vomiting and diarrhoea without other symptoms may be another virus, gastroenteritis.

See a doctor or go to hospital if have other medical conditions or if you are experiencing severe symptoms.

How do I know it’s the flu?

A doctor can diagnose the flu by checking symptoms and taking a swab through your nose, throat or via a blood test.

How long is the flu contagious?

The flu can be spread from a contagious person to others anytime from a day before symptoms appear until about a week later. Children and people with weakened immune systems may be contagious longer.

When is the flu season?

People can catch the flu anytime, but the virus spreads mostly during winter. In Australia, the peak flu season is generally April to October.

The flu can lead to conditions including bronchitis, croup, and ear infections. It can also make chronic existing medical problems worse eg; people with asthma may experience attacks when they have the flu.

More serious flu complications include pneumonia, or an infection deep in your lungs. Flu infections in the respiratory tract can trigger an extreme inflammatory response which causes damage to the cells in the lung. In severe cases, this over reaction can lead to fluid build-up in the airways and multi organ failure. Secondary bacterial infections are also a common complication associated with the flu which may require antibiotics.

When you’re sick with a virus, your body’s immune system builds a defence by making antibodies. These antibodies protect you from getting that virus again. Unfortunately, flu viruses mutate very quickly with new strains appearing each year. Having the flu one year doesn’t protect you from getting it in the future.

If your body encounters a similar influenza strain to one that you have had, the antibodies you have may prevent infection or lessen the severity of the flu. However, antibody levels decline over time and if the flu virus goes through a major change, more people get the flu.

Annual flu vaccination is the best protection against getting the flu or, if you do get it, reducing the severity of the symptoms. Vaccination also prevents the spread to others and is important for protecting high risk groups.

Vaccination each year protects against the three or four influenza viruses that are predicted to be the most common that season.

The best protection against the flu, is prevention through annual vaccination. There are new strains for the flu each year, so a new vaccine is needed each year. Flu vaccination takes two to four weeks to be effective. By building your immunity, a flu vaccine can protect you from getting the flu or if you do get it, reduce the severity if symptoms.

Flu and COVID-19 have separate vaccinations. Having a flu vaccine will reduce the spread to others, which may help people who are more susceptible to other conditions including COVID-19 and reduce the number of people who need hospitalisation.

Most flu cases get better without treatment. Stay at home to prevent the spread to others, rest, drink fluids, preferably water and take paracetamol to help with pain and fever. Antibiotics are not useful for viral infections like the flu. They are only effective for bacterial infections.

Call a doctor or go to hospital if your case is serious – you are getting worse instead of better, you have having trouble breathing or you have a medical condition.

Influenza is different to a cold or COVID-19. For most people, the flu resolves on its own within a week, but for high-risk groups the flu can cause serious complications requiring hospitalisation and it can be fatal.  High-risk groups include

• Babies
• Young children
• Pregnant women
• Women who have just delivered babies
• People aged over 65 years
• People with weakened immune system
• People with underlying chronic lung diseases
• People with underlying heart disease
• People with a body mass index over 40
• People who smoke, those who haven’t had a flu vaccination.

Influenza is mostly caused by type A or B influenza viruses that infect the upper airways and lungs. Type C is less severe. Type A influenza viruses have caused a number of pandemics. There are many sub-types or strains of the flu.

Hudson Institute’s scientific teams also investigate other viruses that cause outbreaks in regions around the world, including rhinoviruses which cause the common cold and exacerbate chronic lung diseases such as asthma and chronic obstructive pulmonary disease, RSV and flaviviruses Dengue and Zika viruses that are transmitted by mosquitos.