Up to 150 million people suffer from asthma in the world and the number has been rising steadily since the 1960s.

In the last 10 years, asthma cases have risen 50% worldwide.

Asthma causes restrictions in breathing, leading to wheezing and breathlessness. This is because it causes narrowing of the bronchial tubes, swelling of their lining and the production of a mucus which can block airways.

The condition proves fatal for around 180,000 of the world's population every year.

In some countries, asthma affects up to 30% of children, while in others, such as Papua New Guinea, it is virtually non-existent.

Scientists do not know what causes it, but they believe a number of factors may be involved, including exposure to indoor or outdoor allergens, smoking, low birth weight, air pollution, genetic factors, respiratory infection and strong drugs.

The conditions can be exacerbated by stress, physical exercise and even weather changes.

One-off incidents

But sometimes one-off incidents can cause asthma attacks.

In London in June 1994, for example, 640 people were rushed to hospital after having asthma attacks.

Many were hayfever sufferers, but had never experienced asthma symptoms before.

A similar freak incident occurred in Melbourne, Australia.

Scientists believe weather conditions, such as thunderstorms, could break up pollen grains which release starch granules that trigger attacks.

The countries which are worst affected by asthma are Ireland, the UK, Australia and New Zealand. Those least affected include Albania, Romania, Georgia and Indonesia.

• In Australia, one child in six under 16 has the condition
• In Western Europe, the number of asthma cases has doubled in the last decade
• in the USA the number has risen by 60% since the early 1980s. Around 5,000 Americans die from asthma each year. Asthma is 26% more prevalent in black than white American children
• around 8% of Swiss people suffer from asthma, compared with just 2% 25 years ago
• there are an estimated four million asthmatics in Germany
• some three million Japanese suffer from the condition, of whom 7% have severe symptoms and 30% have moderate problems.

But asthma, although most associated with industrialisation, is not just a problem of developed countries.

• In India, there are estimated to be up to 20 million asthmatics, with up to 15% of children aged five to 11 years old having symptoms
• in Brazil, Costa Rica, Panama, Peru and Uruguay up to 30% of children are affected by asthma
• 20% of Kenyan children have asthma.

Asthma is the chronic disease most responsible for days off school. Missed days of school can affect a child's future career.

According to Professor Romain Pauwels, chairman of the Global Initiative for Asthma, a third of child asthmatics suffer a great deal of pain or discomfort, including psychological damage which can lead to poor self-esteem and problems forming relationships with peers.

Counting the cost

The economic costs of asthma are estimated to be more than those of HIV/Aids and tuberculosis combined.

In the US, health care for asthmatics and the cost of days lost from work is around $6bn. In the UK it is around $1.8bn. In Australia, medical costs alone total $460m.

The World Health Organisation and the US National Heart, Lung and Blood Institute have formed the Global Initiative for Asthma (GINA) to cut deaths and prevent disability from asthma through a programme of education, treatment and prevention.

This includes combining anti-inflammatory drugs which prevent symptoms and attacks with short-term measures such as inhalers which are used to relieve symptoms.

In countries with access to these drugs, death rates from asthma are decreasing.

GINA has also developed guidelines for on asthma management for doctors, health workers and families as well as reporting on latest developments in the field of asthma.