By Sunil Raman
BBC News, Delhi
India health officials are alarmed by the growing numbers of pregnant women infected with HIV/Aids in the key states of Uttar Pradesh (UP) and Bihar.
India has more HIV infections than any other country, the UN says
The northern states are among India's most backward, with huge populations but poor literacy and health services.
Officials say workers who migrate to cities in search of work bring the infection back to the states with them.
They say unless the state governments get serious about tackling the disease, there could be an Aids epidemic.
According to UN estimates, India has the highest number of HIV infections with 5.7 million people carrying the virus.
The head of India's government-run National Aids Control Organisation (Naco), Sujatha Rao, told the BBC that urgent measures were needed in UP and Bihar to "stem the epidemic".
She was speaking after a countrywide survey to collect India's latest HIV/Aids figures. Full results of the annual Aids survey will be made public in early June.
Ms Rao said the districts of Etawah, Banda and Lalitpur in UP had been found to have more than 1% of pregnant mothers infected with the virus.
A high number of pregnant woman infected with HIV had also been identified in the districts of Lakhiserai and Saharsa of Bihar.
Ms Rao says she is concerned over the slow response of the two state governments in dealing with the problem.
The two state governments have "not realised" the seriousness of the problem but "we remain hopeful", she says.
Ms Rao says the situation in UP and Bihar compares with that in the southern state of Tamil Nadu 10 years ago.
Tamil Nadu is another high prevalence state as far as HIV infections are concerned, but what makes matters far more serious in the two northern states is their poor healthcare system.
To compound matters, Ms Rao says, most cases of HIV/Aids infection in UP and Bihar go unreported because of the social stigma attached to the disease.
The Naco chief's concern is shared by representatives of Aids control programmes in Uttar Pradesh and Bihar, which together have a population of more than 280 million people.
Officials say the virus is spreading to low-risk groups
Health officials say the main cause of the growing incidence of HIV/Aids is migrant labour.
RP Mathur of the Uttar Pradesh Aids Control Authority says around 60% of HIV cases reported come from the socially and economically backward eastern part of the state.
"There is a shift from the urban to rural and from high-risk to low-risk categories" in the last few years, he says.
Mr Mathur says it is estimated that UP has more than half a million HIV positive cases, but only 20,000 of them have been reported, due to the stigma attached to the disease.
Bihar Aids Control Authority representative Vishal Singh says most of the infections have been detected in people who had migrated to work in places outside the state.
"They get infected in industrial cities like Surat [in Gujarat] and return home to Bihar and have unprotected sex with their wives. This has to be controlled," he says.
Mr Singh says given the poor economic situation in Bihar, it is important that more developed states like Gujarat take steps to educate migrants labourers working there.
Rashmi Sharma of the Population Foundation of India, a non-government organisation involved in spreading awareness about HIV/Aids, says migrant labourers cannot solely be blamed.
"A local community will have to take the blame for its inability to control the problem," she says.
"The problem lies within the community and they have to be involved in looking for a solution."
UP and Bihar are two of India's states which rank lowest on the human development index - they have high levels of illiteracy, unemployment and poor social infrastructure.
Officials say it is only the wide gap between the estimated and reported cases which has kept the two states off the list of high prevalence states
Andhra Pradesh, Tamil Nadu and Karnataka in the south, Maharashtra in the west and Manipur and Nagaland in the north-east are considered high HIV prevalence states in India.
There has been much debate about whether India does indeed have more people living with HIV than any other country.
A study by British journal BMC Medicine last December suggested that methods used to estimate the number of infections in India were flawed and that the true figure could be about 40% of the estimated numbers.