Seasonal Flu
Key facts
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There are around a billion cases of seasonal influenza annually, including 3-5 million cases of severe illness
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It differs from pandemic flu in that it is caused by an already circulating flu virus, whereas pandemic flu is a new virus against which people have little or no immunity
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It causes 290,000 to 650,000 deaths every year..
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Flu is very infectious and can easily spread to other people, with people being more likely to give it to others in the first five days.
Overview
Seasonal influenza, or the flu, is a common respiratory illness caused by flu viruses. It's widespread and most people recover without needing medical attention. However, it can be severe or even deadly in some cases. There are four different types of flu virus: A, B, C and D. A and B virus cause seasonal flu.
Flu A includes subtypes like A(H1N1) and A(H3N2), with A(H1N1) being the virus behind the 2009 swine flu pandemic
Signs and symptoms
Flu symptoms start suddenly and typically appear one to four days after infection. Most people recover within a week.
Common symptoms include:
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High fever or chills
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Aches and pains
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Dry cough
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Fatigue
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Sore throat
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Headache
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Runny or stuffy nose
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Some may experience stomach issues like vomiting or diarrhoea, especially children.
The cough can last for two weeks or longer, and not everyone with the flu will have a fever.
Dangers and complications
While most people recover, flu can be more serious in certain high risk groups and can lead to serious complications such as pneumonia and sepsis. It can also worsen the symptoms of people with chronic conditions.
Flu-related hospitalisations and deaths mostly affect high-risk groups:
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People 65 and older
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Pregnant individuals
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Young children (especially under two)
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Those with weakened immune systems
If you or your child shows severe symptoms, seek medical help immediately.
Transmission
Flu spreads easily through respiratory droplets when someone coughs or sneezes. It's most contagious in the first five days. In cold climates, flu seasons peak in winter, but in warmer areas, it can spread year-round.
It can spread easily in crowded places such as schools and nursing homes
Treatment
Most people recover without special treatment. To ease symptoms:
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Rest, stay warm, and drink plenty of fluids
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Take paracetamol or ibuprofen to reduce fever and pain
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Children may need specific dosages for comfort
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Antibiotics don't work for the flu, but antiviral medicines can help if started early, especially for high-risk individuals.
Prevention
The annual flu vaccine is given to certain high risk groups in the UK. While it is less effective in older people, it still reduces severity and complications.
Other prevention tips include:
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Wash your hands often
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Cover your mouth and nose when coughing or sneezing
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Stay home if you're sick and avoid contact with others
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Avoid touching your face
Flu vaccines are updated routinely with new vaccines developed that contain viruses that match those circulating.
History
For many years flu was thought to be a bacterial infection and it was not until the 1930s that the first flu virus was identified.
There have been flu outbreaks and pandemics for many years, with the most well known and deadly in recent times being the 1918 Spanish flu pandemic. It swept around the world as troops came home at the end of the First World War and is estimated to have caused between 50 and 100 million deaths.
It was caused by the influenza A(H1N1) virus and, unlike many flu outbreaks, mainly affected healthy, young people. There were alarming complications such as sufferers turning blue as their bodies were starved of oxygen. Other less serious symptoms included explosive nosebleeds.
More recently, the A(H1N1) virus caused the 2009 swine flu pandemic, which is estimated to have caused around 280,000 deaths.
Seasonal flu vaccines are updated each year based on which strains of the virus are circulating.
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