Background: swine flu
Updated on 30 April 2009
What swine flu is and how the UK is preparing for it.
What is swine flu?
It is a contagious respiratory disease of pigs caused by type A influenza viruses. Pigs are hit by regular outbreaks. There are many different types of swine flu and the current cases involve the H1N1 strain of type A influenza virus. The latest outbreak has seen the constantly changing infection spreading from person to person.
What are the symptoms?
The symptoms of swine influenza in people are similar to the symptoms of regular human seasonal influenza infection and include fever, fatigue, lack of appetite, coughing and sore throat. Some people with swine flu have also reported vomiting and diarrhoea.
What is the difference between swine flu, avian flu and the flu commonly seen in the UK during the winter?
Influenza viruses are commonly circulating in the human and animal environment, with different strains causing illness in humans, bird and pigs. Seasonal influenza is caused by viruses that are adapted to spread in humans.
Humans have some natural immunity to the strains that are in common circulation, and this immunity can be boosted by immunisation with a vaccine. Avian influenza is caused by influenza viruses adapted for infection in birds.
Similarly, swine influenza is caused by influenza viruses adapted for infection in pigs. These illnesses all cause the same respiratory symptoms in sufferers and can be passed between one another.
However swine flu can pass between human to human, while this is rare with avian flu viruses.
How dangerous is it?
Thousands of people have been made ill by swine flu - with some cases, particularly in Mexico, proving fatal.
The World Health Organisation (WHO) has warned the outbreak cannot be contained and has "pandemic potential". It has also raised its alert level to five, one stage below the maximum.
Flu viruses have the ability to change and mutate, making it difficult for drugs manufacturers to ensure effective vaccines are available. Production of a swine flu vaccine could take six months.
The new version of the H1N1 virus is a mix of different animal and human versions of the disease. Mixing can lead to the development of changed viruses to which humans have little immunity.
But testing has shown that the antiviral drugs oseltamavir (Tamiflu) and zanamivir (Relenza) appear to be effective against the human swine influenza H1N1 strain.
What is a pandemic?
If the flu spreads over a wide geographic area and affects a large proportion of the population it goes beyond an epidemic and becomes a pandemic.
According to the Health Protection Agency (HPA), an influenza pandemic is defined as a new or novel influenza virus that spreads easily between humans.
Why have so many people died in Mexico?
The World Health Organisation has said there is no clear reason why the virus seems to have been fatal for so many people in Mexico, while symptoms elsewhere have been mostly mild.
Some experts say that other, unrelated viruses may be circulating in Mexico, making symptoms worse. Those infected outside of Mexico may also have sought treatment at a much earlier stage than those in Mexico.
The virus killing people in Mexico could also be subtly different to that elsewhere.
Is Britain prepared?
Prime Minister Gordon Brown has said Britain is "among the best prepared countries in the world" to deal with the outbreak, and has been preparing for this kind of scenario for many years.
The UK has enough anti-viral drugs, which have been effective against swine flu, for half the population - 33m people - and steps were being taken to increase these stockpiles to cover 50 million people.
Stocks of antibiotics, which treat related infections, are also being increased.
The Health Protection Agency is now also screening passengers on all flights returning from Mexico and offering them information on swine flu.
Airlines have also been asked to retain passenger records for three days, as opposed to the usual 24 hours, to assist with finding people who may have been infected.
What can Britons do to reduce the risk of catching swine flu?
Always use a tissue to catch coughs and sneezes, throw away used tissues and regularly wash your hands with soap and water.
The Foreign Office is also advising Britons to avoid all but essential travel to Mexico.
