Polio making a comeback

The World Health Organization (WHO) says increasing numbers of people around the world are vulnerable to polio because they have not been previously exposed to the disease.

According to the WHO adults who missed being vaccinated as children and who have not been exposed to the wild virus are most at risk.

There have apparently been 19 confirmed and 150 suspected polio cases in Namibia, which had been polio-free since 1995 and immunisation programmes are being implemented there again.

The virus arrived in Namibia by way of Angola but the outbreak has been traced back to Uttar Pradesh in India where the disease remains endemic.

Dr. Bruce Aylward head of the WHO's polio eradication drive, says there are bigger immunisation gaps than at any time in the last 25 years and because people in Namibia had not previously been exposed to polio, they had no defence against the disease.

Aylward says polio must be eradicated everywhere because, while endemic areas persist, the virus will find susceptible people.

Polio is a highly infectious disease which affects the nervous system and can result in paralysis; it is transmitted through contaminated food and drinking water, contact with faeces from an infected person or contaminated swimming pool water.

Although it has been eradicated in much of the world it is still endemic in countries such as Nigeria and India.

Most polio outbreaks as a rule affect children under five but those affected in the Namibian outbreak have been aged between 15 and 45 and the disease is more likely to cause paralysis in adults.

People can acquire an immunity to polio by being infected naturally, through vaccination or by catching the live but weakened version of the virus which is in the oral polio vaccine given to children.

However, natural infections are disappearing and vaccination rates are dropping in many countries as the risk fades.

Also many countries including the UK now use a safer version of the oral vaccine that uses a killed virus, which will not infect others.

Dr. Aylward says that the two ways of preventing the spread of polio were for all countries to aim to vaccinate everyone and for good surveillance to be in place so any outbreaks are picked up early.