Carried out in November by the Central African country's Study Centre for Public Health Development (Credes) with World Bank support, the survey shows that the national average rate of infection is 4,2% among people aged 15 to 49 in a total population approaching three million.

The rate of infection varied considerably from one city to another and according to age group and sex, showed the results of the survey, which was made available by the National Council for Fighting Aids (CNLT) without giving the total number of those tested.

"The outcome means that we're going to have to redouble our efforts with regard to prevention and care for those infected and affected by the Aids virus," CNLT executive secretary Marie Franck Puruhence said.

Puruhence, who is in charge of the Aids programme in the former French colony, western neighbour of the vast Democratic Republic of Congo, added that the survey is the basis for newly developed strategies.

"The risk of being HIV-positive was significantly higher in southern regions than in Brazzaville, and in the central and northern administrative regions," the CNLT report said.

"The pandemic is spreading in the big towns and regions. There is a tendency towards 'feminisation' with an average rate of 4,7% among woman compared with 3,8% among men," it added.

The rate in the southwestern Atlantic port city and oil terminal of Pointe-Noire is 5%, 3,3% in Brazzaville, 9,4% in Dolisie, the third-largest town in the south, and 10,3% in Sibiti, in the southwest.

"The risk ... increases with age, and earlier among women than among men ... It appears clearly that up to the age of 35, women are twice as affected as men."

Among ages by group, the overall rate is "particularly high among those between 35 and 39, with 8,4%, and 40 and 44, with 7,8%."

The main methods of transmitting HIV are unprotected sex, blood transfusions and mother-to-child transmission at childbirth.

The level of education had a marked effect on the results.

The number of HIV-positive people is 5,4% among those without formal education, 4,1% for those who had taken schooling to primary level, 4,8% among those who had completed the first state of secondary education, 3% among college graduates and 2,5% for those who had gone on to university.

In the interest of accuracy, all the HIV-positive samples found during the survey were double-checked at the Bichat hospital in Paris, the CNLT reported.

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