India may be winning the fight against the most dangerous strain of polio, with no cases reported this year in a badly hit region seen as a key global battleground against the paralysing disease, officials said.

India is the focus of concern among the global health community after an outbreak of 676 cases in 2006 -- a tenfold jump over 2005 and one third of the world's total.

The Indian strain caused countries such as Angola and then Namibia to be re-infected, and is thought to be the source of the first outbreak in seven years in neighbouring Myanmar.

Around 96 percent of India's cases in 2006 were of the virulent type 1 strain that paralyses around 1 out of every 200 children infected and travels over wide areas. The majority of cases were reported in western Uttar Pradesh.

"We are making inroads in Uttar Pradesh. In fact, in the last six months, there have not been any cases in western Uttar Pradesh of type 1 polio," said Health Minister Anbumani Ramadoss at a meeting of health officials and experts on Tuesday, referring to the state's worst-hit areas.

Uttar Pradesh is India's most populated state, with 170 million people, and one of its poorest and worst-governed.

Experts say Uttar Pradesh and neighbouring Bihar, with their tropical climate, crowded towns, poor sanitary conditions, high birth rates and widespread diarrhoea among children have been fertile grounds for the polio virus to flourish.

India, which is aims to eradicate polio by the end of 2008, has seen 103 cases of polio this year against 150 till the end of June last year, but, more importantly, type 1 cases in the first six months have fallen to 39 against 145 year-on-year.

Crucially, no child has been affected by the type 1 strain in the seven worst-affected districts of Uttar Pradesh this year.

"TRANSITION POINT"

"We are at a transition point in the fight against the type 1 virus, and once we decisively win the battle, we will go after type 3," said Dr. Hamid Jafari, project manager of WHO's National Polio Surveillance Project in India.

"We now have an unique opportunity to terminate type 1 transmission as the most severely endemic areas in Uttar Pradesh have not recorded any case for months."

As a result of the greater focus on immunising children against type 1 there has been a spike in the cases of less virulent type 3 polio, which should not cause alarm, Jafari said.

"We should not get shaken by a rise in the type 3 as we have to succeed against type 1 first," he said.

In the past India has been using a trivalent vaccine that protects against all three types of polio, but found it was not effective enough against the virulent type 1 strain.

As a result it has switched to using a monovalent vaccine specifically aimed at the type 1 strain in many areas.

The type 3 strain paralyses one in around 1,000 children infected and does not travel so far. Type 2 polio was last recorded in the world in western Uttar Pradesh in 1999.

Apart from India, polio still lingers in Pakistan, Afghanistan and Nigeria.