Bihar is one of the poorest states in the country and hence among the biggest suppliers of migrant labourers.

Whether it's seasonal farm hands for Punjab or construction workers for the skyscrapers in Mumbai and Delhi or new suburbs of Kolkata, daily wagers come mostly from Bihar or adjoining districts of UP.

Bihar State health secretary Deepak Kumar told The Times of India : "Our prevalence rates compare with some of the other high-risk states in the country. Till now, everybody thought that AIDS was not a problem in Bihar. We plan to concentrate on the high-prevalence districts to spread greater awareness."

 Expressing fear that the state was on the brink of an epidemic, a senior BSACS official said: "The rate at which the infection is spreading, very soon, it may cross the 1% prevalence rate."

He added that the surveys were conducted among the general population.

"We deliberately chose the remotest of villages in every district to get genuine figures among the rural population. Samples found positive were tested two more times before confirming," said the official.

The eight districts on the red list are: Sitamarhi (prevalence rate of 3.7%), East Champaran (2.28 %), Khagaria (1.89%), Kishanganj (1.52%), Madhubani (1.26%), Muzaffarpur (1.07%), West Champaran (1.28%) and Purnia (1.81%).

 These districts are among the poorest in Bihar and have huge migrant populations. Most of the districts also share borders with Nepal.

The official said: "The high prevalence rates are a direct fallout of the extreme poverty in these districts and the high migration rates. Due to lack of employment opportunities, most men in rural Bihar migrate to Punjab, Haryana, Gujarat, Maharashtra and other states to work as labourers and most likely, spread the infection to their wives in the villages."

Officials said the huge chasm in estimates arose from the fact that NACO never surveyed people in villages and depended on hospital figures.