Q&A: Polio

Mass vaccination helps reduce the risk

Polio once crippled thousands of children every year in industrialised nations.

The advent of vaccines in the late 1950s effectively ended the threat to the developed countries.

The disease has now been eliminated from most of the world.

However, it remains a threat in a handful of countries.

India, Nigeria and Pakistan together account for 98% of all global cases.

Other hotspots are Niger, Afghanistan and Egypt.

What is Polio?

Poliomyelitis (polio) is a highly infectious disease caused by a virus.

The virus usually enters the body via the mouth, and multiplies in the gut.

Once established it can enter the blood stream and then invade the central nervous system.

As it multiplies, the virus destroys nerve cells which activate muscles.

What are the symptoms?

Most people infected by the virus show no signs of ill health.

However, infection can cause fever, fatigue, headache, vomiting, stiffness in the neck and pain in the limbs.

Around one in 200 people who are infected become irreversibly paralysed.

The virus most often attacks the nerve cells which control the leg muscles, causing the limb to become floppy and lifeless - a condition known as acute flaccid paralysis (AFP).

More extensive paralysis, resulting in quadriplegia, is rarer.

In the most severe cases the virus attacks nerve cells in the brain that control swallowing, speaking and breathing. This can be deadly.

Who is most at risk?

Polio can strike at any age, but more than half of all cases affect children under the age of three.

How is it spread?

In countries where polio is endemic, the virus is mainly passed through person-to-person contact.

The virus also lives in the faeces of infected people, in some cases even those who have been vaccinated against the disease, and can spread quickly in areas where sewerage or sanitation is poor.

How is polio treated?

There is no cure for the disease. It can only be prevented through immunisation.

Polio vaccine, given multiple times, almost always protects a child for life.

Physical therapy and drugs are used to ease muscular problems, but there is no way to reverse permanent polio paralysis.

Is there an attempt to eradicate the virus?

Yes. The Global Polio Eradication Initiative was launched in 1988, when 350,000 people were still infected with the virus every year.

Since then tremendous progress has been made thanks to mass vaccination programmes.

However, it is thought that in some areas 20% of children are being missed - giving the virus enough breathing room to survive.

It seems unlikely that the initiative will meet its aim of complete eradication of the disease by the end of 2005.