Swine flu (H1N1) 


Swine flu is the H1N1 strain of the virus that caused a pandemic in 2009 

The swine flu pandemic

In 2009, swine flu spread quickly around the world, before dying down in the spring of 2010. This type of global outbreak is known as a pandemic.

The virus was first identified in Mexico in April 2009. It spread rapidly from country to country because it was a new type of flu virus that few people had full resistance to.

Flu pandemics are a natural event that occur from time to time. In the last century, there were flu pandemics in 1918, 1957 and 1968, when millions of people died across the world.

The 2009 swine flu virus proved to be relatively mild and the pandemic was not as serious as originally predicted. As in other countries, most cases reported in the UK were mild.

There were a small number of cases that resulted in serious illness and death. These were mostly in people with pre-existing health conditions, such as cancer, that had already weakened their immune systems.

Swine flu is a relatively new strain of influenza (flu) that was responsible for a flu pandemic during 2009-2010.

It is sometimes known as H1N1 influenza because it is the H1N1 strain of virus.

On 10 August 2010, the World Health Organization (WHO) declared that the swine flu pandemic was officially over. However, this does not mean that swine flu can be ignored.

The swine flu virus will be one of the main viruses circulating this winter. It has therefore been included in the 2012-13 seasonal flu vaccine.


It is recommended that people in high-risk groups be vaccinated against swine flu. This includes all pregnant women, at any stage of pregnancy.

Pregnant women in high-risk groups and those not in high-risk groups are advised to take the seasonal flu jab, which protects against swine flu.

This is because there is good evidence that all pregnant women are at increased risk from complications if they catch swine flu. For more information, see swine flu advice for pregnant women.

For general information about flu, see seasonal flu and seasonal flu jab

What to do if you have swine flu

People with swine flu typically have a fever or high temperature (over 38C or 100.4F) and may also have aching muscles, sore throat or a dry cough (see symptoms of swine flu). The symptoms are very similar to other types of seasonal flu. Most people recover within a week, even without special treatment.

Contact your GP if you think you have swine flu and you are worried. They will decide the most appropriate action to take.

The National Pandemic Flu Service no longer operates.

High-risk groups 

Some people are more at risk of complications if they catch flu. People are particularly vulnerable if they have:

Also at risk are:

  • patients who have had drug treatment for asthma in the past three years
  • pregnant women
  • people who are 65 years of age or over

See preventing swine flu for a full list of people advised to have this year's flu jab.

Preventing the spread of swine flu

The most important way to stop flu spreading is to have good respiratory and hand hygiene. This means sneezing into a tissue and quickly putting it in a bin. Wash your hands and work surfaces regularly and thoroughly to kill the virus.

Anyone who is concerned about flu symptoms should contact their GP, who will determine the most appropriate action to take.

For more information about how the H1N1 virus spreads, see causes of swine flu.

Page last reviewed: 12/10/2012

Next review due: 12/10/2014


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