The number of people with HIV/Aids is rising in West Africa, according to the United Nations.

A report being published on Tuesday warns of the spread of HIV in the region, despite many countries having had stable rates of the disease in the past five to eight years.

One of the real concerns has to do with Cameroon

Dr Neff Walker

Conflict and the growth of towns and cities are among the reasons why HIV/Aids is increasing in West Africa, according to Dr Neff Walker, an epidemiologist with UNAids.

Dr Walker told the BBC's Network Africa programme that a more virulent strain of the virus, which has been prevalent in southern Africa, was now spreading to the west of the continent.

'Scary'

He said the fact that the prevalence of HIV/Aids had risen in a country like Cameroon was "scary".

	:	Aids in Africa
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"One of the real concerns has to do with Cameroon," Dr Walker said.

He said the HIV/Aids rate in the country had nearly doubled in the past few years, from a rate of about 6% to nearly 12%.

Dr Walker said there were signs of the same thing happening in Nigeria.

More than 12 million children have been orphaned by Aids worldwide

Migration has encouraged the spread to West Africa of a more virulent strain of the virus called HIV1.

Patients with the virus are expected to live for nine or 10 years, as opposed to 30 to 40 years with HIV2.

HIV2 has been more prevalent in West Africa but the more virulent strain is set to push it out, Dr Walker said.

He said that one of the most shocking findings in the report was that in some urban areas in Botswana, 60% of pregnant women aged between 25 and 29 had HIV/Aids.

He said that many people found such high rates "unbelievable", partly because it takes a while for the effects of HIV/Aids to become apparent in society.