Influenza – the flu
Most of us have had our fair share of colds and flu, especially during winter months. But while a cold can make you feel under the weather, it’s not the same as the flu. Having influenza can make you feel miserable and tends to lay you flat for at least a few days, and often for a week or so.
So, how do you know if it’s a cold or the flu? Typical symptoms of flu include:
- reduced appetite;
- tiredness and weakness (often severe);
- runny nose and sneezing;
- cough (usually a dry cough);
- sore throat;
- muscle aches and pains (which are more common in children and tend to affect the legs and back especially); and
- joint pains.
Children may also have abdominal pain, nausea and vomiting.
People often mistakenly say they have ‘the flu’ when it is actually a cold, because several of the symptoms (such as runny nose, sore throat and cough) are similar. In general, people with the flu develop symptoms more suddenly and are much more unwell. Those with colds rarely have high fevers, muscle and joint pains or extreme tiredness and weakness.
Some people with flu have a fever and muscle aches with few other symptoms.
How long does the flu last?
Flu symptoms tend to come on suddenly, usually about 2 days after becoming infected. The flu typically lasts about a week, but tiredness, fatigue and cough may persist for longer. Cough can last 2 weeks or more, and tiredness can persist for several weeks after a bout of flu.
What causes influenza?
Influenza is caused by catching an influenza virus, which infects the nose, throat and sometimes lungs.
There are several types of influenza virus – influenza A and B are the main types that cause disease in humans. These viruses constantly change and mutate, creating different strains and subtypes. So having had the flu before doesn’t stop us getting it again.
Influenza frequently occurs in epidemics, most commonly in autumn and winter. From time to time, new strains emerge that can cause serious illness and death, even in healthy, young people. Sometimes when a new strain emerges it can spread across the globe — a so-called pandemic.
The peak time when most people in Australia get influenza is between May and September. In Australia, there are about 100 reported influenza deaths each year, and more than 5000 hospitalisations due to flu. However, it’s thought that the actual numbers are much higher than this.
How did I get the flu?
Influenza viruses are very infectious and can easily spread from person to person.
You can catch influenza through:
- direct contact with someone who is infected;
- touching contaminated objects (such as door handles) which can be infectious for hours; or
- inhaling the fine droplets that are shot from the nose and mouth when an infected person coughs, sneezes or talks.
Anyone can get the flu but it can be particularly severe in young children, pregnant women, older people and those with other health problems.
How long are people with flu contagious?
You may be infectious for a day before flu symptoms start, but people tend to be most infectious during the first 2 to 3 days of the illness.
Within 10 days, most people are no longer contagious. However, children may remain infectious for up to 2 weeks, and people with conditions that affect their immune system can still be infectious for weeks or months.
Your risk of catching the flu is higher if someone in your household is infected and you have not been vaccinated. Healthcare workers also have a higher risk of getting flu.
As well as catching it from an infected person, you can catch the flu from inanimate objects. The flu virus can survive for 24 hours on hard surfaces such as door handles and phones, but only minutes on a person’s hands. The viruses can also survive in droplets in the air for a few hours, and low temperatures prolong their survival.
Pneumonia is a common complication of influenza. The influenza virus can infect the lungs (causing viral pneumonia), or a bacterial infection can develop on top of the influenza infection, causing bacterial pneumonia.
Less common serious complications that can develop include inflammation of the muscles, heart, or brain.
Some people have a higher risk of developing complications and severe influenza than others. People at increased risk include:
- children younger than 5 years;
- people aged 65 years and older;
- Indigenous Australians;
- people who smoke;
- people with chronic (ongoing) illnesses; and
- pregnant women.
Tests and diagnosis
Your doctor may suspect you have flu based on your symptoms and physical examination findings, especially if your symptoms develop in autumn or winter (flu season).
In some cases, tests may be recommended to confirm the diagnosis or to rule out complications. Swab tests can be taken from the back of the nose or throat to be tested for the influenza virus in a laboratory. There are also rapid influenza tests that can give results in about 15 minutes but are less reliable and specific.
A chest X-ray may be recommended if you have a cough or are short of breath, to rule out a chest infection or pneumonia.
Treating the flu
Most people get better from an episode of the flu without specific treatment, using self-care measures and over-the-counter medicines to help relieve symptoms. There are also antiviral medicines available that can help you feel better faster, but these medicines are not routinely recommended for everyone who gets the flu. Antibiotics are not effective against viruses, so don’t help unless you get a bacterial infection following the flu (which sometimes happens).
Antiviral medicines can reduce the amount of time you are unwell with influenza by a day or 2. They can also reduce the severity of your symptoms and help prevent complications. Treatment with antiviral medicines may also reduce the risk of you passing the virus on to someone else.
Antivirals provide most benefit when taken within 48 hours of symptoms developing. Available antiviral medicines include oseltamivir (brand name Tamiflu) and zanamivir (brand name Relenza).
Antivirals are usually only used in people who have, or are at increased risk of, severe disease or complications of influenza. Most people get better within a week without taking antiviral medicines.
Possible side effects associated with antiviral medicines include nausea and vomiting, dizziness, delirium and diarrhoea.
Cold and flu medicines
There are a variety of medicines that can help relieve the symptoms of the flu in adults. Cold and flu medicines should not be used by children younger than 6 years. For older children, always check with your doctor or pharmacist whether the product is safe for your child. Do not give any formulation containing aspirin to children or teenagers.
Combination cold and flu medicines generally contain several ingredients – pain relievers (to relieve symptoms of fever as well as pain), decongestants (for a blocked or runny nose) and cough suppressants may be included. Ask your pharmacist for help in selecting the medicine that is best for your symptoms.
Take care to carefully read the ingredients of any cold or flu formulations that you take so that you don’t double up on ingredients, especially paracetamol, ibuprofen or antihistamines. If you take a combination product and then also take additional medicines, you risk overdosing on some types of medicines.
Side effects of cold and flu preparations will depend on the formulation used.
The following measures can help you feel better when you have the flu.
- Getting plenty of rest.
- Drinking plenty of liquids (such as water, fruit juice, cordial, soups). This is very important when you are sweating and feverish.
- Avoid alcohol as it can lead to dehydration.
- Fresh lemon juice mixed with some honey and hot water can soothe a sore throat or dry cough.
Many self-help measures that help with colds can also help relieve some of the symptoms of the flu.
When should I see my doctor about flu?
Most people get better from flu with rest, self-care measures and over-the-counter medicines. It often takes up to a week to feel better, so if you will be absent from work or study, you may need to see your doctor for a doctor’s certificate.
You should see your doctor sooner rather than later if children or older people develop symptoms of flu. They tend to be more severely affected. Similarly, people with existing health problems such as heart or lung problems should see their doctor sooner rather than later.
Also see your doctor if you (or someone you are caring for) have influenza and:
- develop a very high fever (above 40°C);
- become short of breath;
- have chest pains;
- are not eating or drinking;
- have productive cough (a cough with phlegm);
- have severe muscle pain that makes walking difficult or very painful;
- have symptoms that are not improving;
- have symptoms that are getting worse;
- become confused; or
- you have reason to believe you may have been exposed to a new type of flu, such as swine flu or bird flu (avian influenza).
Being vaccinated against influenza is recommended for anyone who wants to reduce the likelihood of catching influenza.
If you are at high risk of getting influenza, are more likely to have complications or are in an essential service (such as healthcare workers) your doctor may strongly recommend you have an influenza vaccination.
In Australia, flu vaccination is provided free for:
- anyone aged 65 years and older;
- pregnant women;
- those who have long-term health problems (for example, asthma or diabetes); and
- Aboriginal or Torres Strait Islander children aged 6 months to 5 years and people 15 years and older.
New vaccines are made each year, depending on the type of virus that is circulating. They are generally released for use at about the beginning of March, and to maintain protection, you should be re-vaccinated every autumn.
Influenza vaccines should not be given to babies under 6 months of age or people who have had a severe allergic reaction (anaphylaxis) to a flu vaccine before. Care should be taken in people who have extremely severe allergies to hen’s eggs.
The influenza vaccine will improve your chances of not getting the flu, but does not give 100 per cent protection.
Antiviral medicines are sometimes given to people who have been exposed to influenza to prevent them from developing the infection. This is known as antiviral prophylaxis (or postexposure prophylaxis) and is usually considered for close contacts of people with influenza who are also at risk of developing severe disease.
To help control the spread of infections, practise the following measures.
- Frequently wash your hands using soap and water. Dry them properly after washing.
- Practise basic cough etiquette: cover your mouth and nose when you sneeze or cough. Sneeze or cough into a tissue or into the crook of your elbow, rather than into your hands. Throw tissues into the bin straight after use and wash your hands afterwards.
- Stay at home and avoid school, work and other crowded places when you are sick.
Last Reviewed: 07/03/2019
Your Doctor. Dr Michael Jones, Medical Editor.
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3. Influenza (published November 2014). In: eTG complete. Melbourne: Therapeutic Guidelines Limited; 2019 Jan. https://tgldcdp.tg.org.au (accessed Feb 2019).
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