Swine flu is the popular name for influenza (flu) caused by a relatively new strain of influenza virus A. It was responsible for the flu pandemic in 2009-10.
The virus is officially known as influenza virus A/H1N1pdm09.
The swine flu pandemic
The virus was first identified in Mexico in April 2009 and was also known as Mexican flu. It became known as swine flu because the virus closely resembled known influenza viruses that cause illness in pigs.
It spread rapidly from country to country because it was a new type of flu virus that few people were immune to.
The pandemic proved to be relatively mild and was not as serious as originally predicted. As in other countries, most cases reported in the UK were mild.
However, a small number of cases resulted in serious illness and death. These were mostly in the very elderly, very young, pregnant women, or people with a pre-existing health condition, such as cancer, that had already weakened their immune systems.
On August 10 2010, the World Health Organization (WHO) declared the pandemic was officially over.
The virus now circulates worldwide as one of three seasonal flu viruses. The other viruses are influenza virus B and influenza virus A/H3N2.
The symptoms of flu caused by the H1N1pdm09 virus are similar to those of other types, and include:
a sudden fever – a temperature of 38C (100.4F) or above
aching muscles or joint pain
a runny or blocked nose
Most people recover within a week, even without special treatment.
However, some people are at a higher risk of complications and are recommended to have the seasonal flu jab. The 2014-15 seasonal flu jab includes protection against three types of flu virus, including H1N1pdm09.
When to see your GP
If you are otherwise fit and healthy, there is usually no need to visit your GP if you have flu-like symptoms.
See your GP if you have flu-like symptoms and are at a higher risk of complications of seasonal flu. This includes:
children under two years old
anyone over the age of 65
children and adults with an underlying health condition (particularly long-term heart or respiratory disease)
children and adults with weakened immune systems
The seasonal flu jab is available for free for those at risk and is given as an annual injection to:
adults over the age of 18 at risk of flu (including everyone over 65)
children aged from six months to two years who are at risk of flu
The flu vaccine is also given as an annual nasal spray to:
children aged 2 to 18 years at risk of flu
healthy children aged two, three and four
How is swine flu treated?
The best remedy is to rest at home, keep warm and drink plenty of water to avoid dehydration.
You can take paracetamol or ibuprofen to lower a high temperature and relieve aches.
If further treatment is needed or complications develop, medication is available to treat flu caused by the H1N1pdm09 virus. This includes:
antiviral medications – oseltamivir (Tamiflu) and zanamivir (Relenza) help relieve symptoms and reduce the risk of serious complications
antibiotics – to combat bacterial infections such as pneumonia, which may occur as a complication of influenza
If you are prescribed antivirals, you will need to pay a prescription charge (unless your prescriptions are normally free of charge).
Preventing the spread of flu
The H1N1pdm09 virus is spread in exactly the same way as the common cold and other flu viruses.
The virus is contained in the millions of tiny droplets that come out of the nose and mouth when someone coughs or sneezes.
These droplets typically spread about 1 metre (3 feet). They hang suspended in the air for a while, but then land on surfaces, where the virus can survive for up to 24 hours.
Anyone who touches these surfaces can spread the virus by touching anything else. The virus is also transmitted by infected people who cough or sneeze into their hands and then touch other people or objects before washing their hands.
Everyday items at home and in public places may have traces of the virus. These include food, door handles, remote controls, hand rails, paper money and computer keyboards.
People usually become infected by picking up the virus on their hands from contaminated objects and then placing their hands near their mouth or nose. It is also possible to breathe in the virus if it is suspended in airborne droplets.
Good hygiene, such as hand washing and cleaning, is the most effective way of slowing the spread of flu. Antiviral medication and the seasonal flu jab are also offered to people at risk.