Mexican swine flu: What you need to know

27 April, 2009

Mexican swine flu is a form of influenza that originated in pigs but can be caught by, and spread among, people.

Swine flu is a respiratory disease of pigs caused by type A influenza viruses. Outbreaks of swine flu happen regularly in pigs. People do not normally get swine influenza, though infections do sometimes happen. In the recent past, most human cases of swine influenza have been in people who were in close contact with pigs, such as farmers. In the current outbreak the virus has been spread by person-to-person contact.

In the Mexican swine flu outbreak, human infection with swine influenza A (H1N1) viruses have also been confirmed in the US, Canada, Spain and the UK.

This has given rise to concern that the outbreak could become a pandemic flu - a global outbreak of flu that spreads quickly because it is a new type of virus that few, if any, people have resistance to.

A flu pandemic is a natural event that occurs from time to time. Last century, there were flu pandemics in 1918, 1957 and 1968, when millions of people died across the world.

Experts warn that another flu pandemic could happen soon, but they do not know when.

These pages aim to inform you about the Mexican swine flu outbreak and pandemic flu and advise on the important measures to take if a flu pandemic breaks out.

How is it different from seasonal flu, bird flu or swine flu?

Seasonal flu, caused by an existing flu virus, is a common infection in the UK that usually occurs during a two-month period in winter. For most people, it is an unpleasant but not life-threatening infection. People who are more at risk from it, such as older people, can be given a vaccine each year (see Useful links for more information).

Bird flu and swine flu are types of flu that occur in birds and animals and do not normally spread to humans. But if they do spread, it can be very serious and can cause death.

A pandemic occurs when a new flu virus appears in the human population and spreads from person to person worldwide. It is likely that such a virus will be caused by a bird or animal virus mixing with the human virus (see Causes).

It is expected that an outbreak of pandemic flu will cause more illness and many more deaths than ordinary flu.

Is a flu pandemic imminent?

A pandemic could happen any time, but we cannot predict exactly when it would start. The Mexican swine flu virus could lead to a pandemic. The World Health Organization (WHO) is closely monitoring cases of this new flu virus.

The WHO has defined stages in the progression of a pandemic. We are currently at Phase Four of six phases (a pandemic is confirmed at Phase Six).

What can we do?

The single most effective way to stop or slow the spread of diseases such as pandemic flu is to prevent the spread of germs. Wash your hands regularly with soap and water and cover your mouth if you cough or sneeze (see Prevention for more detailed information).

You should also think about what you would do if you and your family all became ill. Who could you rely on for support, such as to collect medicines or shop for you? What food and other supplies should you keep a store of at home?

What is the government doing to prepare?

GPs and hospitals across the UK are preparing for a pandemic, and the UK government is working with the WHO to monitor the situation.

If pandemic flu does arrive in the UK, antiviral medicine will be used to treat people who become ill (see Treatment).

While the development of a vaccine can only start once the new virus has been identified, the UK has agreements with manufacturers, which will produce a vaccine when it becomes available.

Causes

Why it spreads quickly

Evidence from previous pandemics suggests that one person will infect about two others, and that influenza spreads particularly rapidly in closed communities such as schools or residential homes.

People are most infectious soon after they develop symptoms, although they can spread the virus for up to five days after the start of symptoms (for children this is seven days).

Flu viruses are always changing, and new strains emerge every year. If a flu virus appears that is very different from the others, most people will not have immunity to it, and it may spread quickly and become a pandemic.

Concerns have recently increased due to the spread of swine flu in Mexico. A strain of flu that usually only affects animals has infected people and caused serious illness and deaths.

This new virus could potentially cause a pandemic.

How the flu virus spreads

The Mexican swine flu virus is spread in exactly the same way as ordinary colds and flu.

A flu virus is made up of tiny particles that can be spread through the droplets that come out of the nose and mouth when someone coughs or sneezes.

If someone coughs or sneezes and they do not cover it, those droplets can spread about one metre (3ft). If you are very close to the person you might breathe them in.

Or, if someone coughs or sneezes into their hand, those droplets and the virus within them are easily transferred to surfaces that the person touches.

Everyday items at home and in public places may have traces of the virus, such as door handles, the TV remote control, hand rails and computer keyboards. Viruses can survive for several hours on these surfaces.

If you touch these surfaces and touch your face, the virus can enter your system, and you can become infected.

Symptoms of pandemic flu

The symptoms of Mexican swine flu are broadly the same as those of ordinary flu, but may be more severe and cause more serious complications.

The typical symptoms are:

sudden fever, and
sudden cough.

Other symptoms may include:

headache,
tiredness,
chills,
aching muscles,
diarrhoea or stomach upset,
sore throat,
runny nose,
sneezing, and
loss of appetite.

Potentially, everyone is at risk from pandemic flu because few people, if any at all, will have immunity (resistance) to it.

If you have any of these symptoms but a flu pandemic has not been announced, you could have seasonal flu.

Treating pandemic flu

The UK government has drawn up a national framework for preparing for a flu pandemic.

If the Mexican swine flu outbreak became a pandemic, it would have a big impact on NHS services and our daily lives. The national framework includes making sure that the NHS is as prepared as it can be, and that treatment would reach people as soon as possible. It aims to protect the public by minimising disruption and the spread of the infection.

Antivirals

One of the ways to lessen the symptoms of pandemic flu is to treat infected people with antiviral medicine. The UK has stocks of this medicine and there is enough to treat up to half the population should they become ill during a pandemic.

Antivirals will help to:

reduce the length of time you are ill by around one day,
relieve some of the symptoms, and
reduce the potential for serious complications such as pneumonia.

Antivirals will not cure you, but they lessen the symptoms and help you to recover.

Combating pandemic flu

Preventing the spread of germs is the single most effective way to slow the spread of diseases like pandemic flu.

You can protect yourself and your patients by:

ensuring everyone washes their hands regularly with soap and water, and
cleaning surfaces regularly.

You can prevent a virus spreading to others by:

always carrying tissues,
using tissues to cover your mouth and nose when you cough and sneeze,
binning the tissues as soon as possible, and
washing your hands regularly.

CATCH IT. BIN IT. KILL IT. is a simple way to remember this.

Why vaccination cannot prevent the start of a pandemic

The government is unable to vaccinate the population against the spread of pandemic flu because a vaccine cannot be made in advance of the virus being identified. As the virus will be a new strain, a vaccine must be developed specifically to match this.

Since work on producing a vaccine can only begin once that strain has been identified, it is unlikely to be available during the early stages of the pandemic and will take months to produce, and considerably longer to produce in sufficient quantities to treat the entire population.