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About pandemic flu

A pandemic is a global disease outbreak. Pandemic flu occurs when a new influenza virus emerges for which people have little or no immunity, and for which there is no vaccine. The disease spreads easily from person to person, causes serious illness and can sweep across the country in which it originates and around the world in a very short time.

In contrast to the ‘ordinary’ or ‘seasonal’, flu outbreaks which we see every winter in the UK, flu pandemics occur infrequently - usually every few decades. There were three last century. The most serious was in 1918, killing millions of people worldwide and smaller pandemics happened in 1957 and 1968.

Are we at risk now?

A pandemic can only start when three conditions have been met:

1. a new influenza virus subtype emerges;
2. it infects humans, causing serious illness; and
3. it spreads easily and sustainably among humans.
   

The H5N1 virus meets the first two conditions and it is likely that nobody will have immunity should an H5N1-like pandemic virus emerge. The H5N1 virus has not yet demonstrated the ability to pass easily between people. However, the virus is currently passing from birds to humans so it could develop the ability to pass easilly between people. These opportunities will also persist as long as the virus continues to circulate in birds.

When will a pandemic arrive in UK?

We do not know – it can’t be predicted. The gaps between previous pandemics have varied widely. Intervals between previous pandemics have varied from 11 to 42 years with no recognisable pattern. Three influenza pandemics occurred in the last century – 1918/19 (Spanish flu), 1957/58 (Asian flu) and 1968/69 (Hong Kong flu). All affected large numbers of the population, causing many deaths and huge economic and social disruption.

Experts are concerned that the H5N1 avian flu virus, which has gained the ability to pass from birds in order to cause disease and death in humans, may emerge to form a pandemic.

How long will it take to arrive in UK?

Probably less than six months and possibly just a few weeks or less, but this will depend upon where the pandemic emerges. Of course, it is important to remember that the pandemic could emerge in the UK. The increasing speed and volume of modern travel means infectious diseases can travel very rapidly around the globe.

Can it be prevented at any stage?

International effort will be made in trying to control a pandemic when it emerges. However, influenza is highly infectious and because whole populations will be susceptible to the new virus, despite people’s best efforts, it is likely to continue to spread.

The World Health Organisation (WHO) has purchased a stockpile of antivirals which can be transported to the source of the outbreak. It is hoped that these antivirals may help to contain the emerging virus.

Why is there so much concern about outbreaks of H5N1?

H5N1 is of particular concern because:

• it is especially virulent
• it is being spread by migratory birds
• it can be transmitted from birds to mammals and in some limited circumstances to humans
• like other viruses, it continues to evolve.

Who is at risk?

We cannot know which groups will be affected by pandemic flu until the virus emerges. However, we know from previous pandemics that a future one is likely to have a major impact worldwide and from experience of previous pandemics we know that it is not necessarily the young and the elderly that will be affected.

How is the virus spread?

The virus is easily passed from person to person by breathing in air containing the virus produced when an infected person talks, coughs or sneezes. It can also spread through hand/ face contact after touching a person or surface contaminated with the virus.

Symptoms

Pandemic flu is likely to cause the same symptoms as ordinary flu but the symptoms may be more severe because nobody will have any immunity or protection against that particular virus. People infected with the current strand of the avian virus (H5N1) have shown everything from typical human influenza-like symptoms (fever, cough, sore throat, and muscle aches) to pneumonia, severe respiratory diseases, and other life-threatening complications.