Influenza
What is flu?
Flu (or Influenza) is an infection caused by the influenza virus that commonly affects the respiratory tract – nose, throat and lungs. It can pass easily between people and is more common in winter.
Most people recover from flu after about a week but some people can become seriously unwell, need to go to hospital or even die from the complications caused by flu.
Types of flu
There are three main types of influenza virus: Influenza A, B & C.
Types A & B are responsible for the seasonal flu outbreaks we see each year.
Why flu changes yearly
Flu viruses change or evolve over time. Small changes happen regularly, which is why new or different strains of flu circulate each year and why flu vaccines are updated annually. Very rarely, major changes can occur that allow a whole new subtype of flu virus to spread widely in people. This can lead to a pandemic, such as the 2009 “swine flu” outbreak.
Who is more at risk from flu?
Flu can be more serious for some people. This means they are more likely to develop serious complications. Flu can be more serious for the following groups:
- Very young babies
- Older adults
- Pregnant women
- People with long-term health conditions including weakened immune systems
Along with healthcare workers, groups that are at greater risk of becoming seriously unwell with flu are offered the annual flu vaccine to protect themselves. Though young babies are not routinely offered the flu vaccine until they are 2 years old, the maternal vaccine for pregnant women offers protection to very young babies when they are first born.
More information on the flu vaccination, including eligible groups, can be found at the following link: NHS flu vaccine.
How is flu spread?
Flu is spread through the air, such as when an infected person coughs or sneezes. The virus can be breathed in directly or picked up from surfaces by touch, for example when someone touches a contaminated surface and then their mouth or nose.
What are the symptoms of flu?
Flu can cause a range of symptoms including:
- Fever
- Chills
- Headache
- Muscle and body aches
- Fatigue
- Cough
- Sore throat
- Runny or blocked nose
- Sickness or diarrhoea
What are the complications of flu?
Flu can cause complications such as:
- Sinus or ear infections
- Viral pneumonia caused by the flu virus or secondary bacterial pneumonia
- Flu can also cause non-respiratory complications in different parts of the body including in the cardiac and neurological systems
- Flu can also cause other medical conditions such as Asthma to get worse
For more information on flu, including treatment, please see the NHS guidance.