Aids could cut population numbers in some of the worst-hit African countries - the first falls attributable to disease since bubonic plague ravaged Europe.

The ferocious rise of Aids in countries such as Botswana, South Africa and Zimbabwe could lead to dropping populations by the year 2003.

We continue to underestimate this epidemic

Paul Delay, US government aids specialist

This would be the first time countries have experienced shrinking populations due to disease since the black death struck Europe in the 1300s.

An estimated 25 million died in that outbreak, and it took until the start of the 16th century before population levels recovered.

Karen Stanecki, a leading US demographer, picked out seven southern African countries which were at risk of experiencing population falls if current trends continue.

They are Botswana, Lesotho, Namibia, South Africa, Swaziland, Zambia and Zimbabwe.

She said: "By 2003, Botswana, South Africa and Zimbabwe will be experiencing negative population growth of one to three percent."

She said that it could take up to 50 years for these countries' populations to recover.

Young victims

The problem has been accentuated by the fact that the majority of those dying from the virus are younger, thus increasing the burden of the disease on the economy.

In some countries there is a critical shortage of teachers, health workers, civil servants and experienced military officers.

A South African mother and child are HIV positive

Ms Stanecki pointed out that the toll even among children was immense: "80% of deaths of children under five in Zimbabwe in 2010 will be due to Aids."

Paul Delay, a specialist with the US government's aid organisation USAID, admitted that many experts had been caught be surprise by the speed of the spread of Aids.

He said: "We continue to underestimate this epidemic."

In South Africa, far more women than men are dying from Aids - this has led to a huge imbalance in the population.

Several African countries have average life expectancies below 40 years, and still falling.

Normally, without Aids, life expectancy would on average be above 50 years.

Meanwhile, experts have warned that the Aids epidemic in India could soon match the scale of Africa.

"India cannot afford to go down the same road as Africa," said Ishwar Gilada, secretary general of the Peoples Health Organisation.

Unofficial estimates put the number of HIV-infected Indians at near five million.

Gilada said: "Aids is public enemy number one and we must treat it as such. If we don't treat Aids as a battlefront, we will lose the war."