India has marked three years since its last polio case was reported, a major milestone in eradicating the disease.

The marker puts the country on course to being formally declared polio-free in March. The World Health Organisation (WHO) still needs to confirm there are no undetected cases before making the official declaration.

Polio is a vaccine-preventable disease that has been eradicated in most countries. But it still causes paralysis or death in some parts of the world, including Nigeria, Pakistan and Afghanistan.

Polio usually infects children under five when they drink contaminated water. The virus attacks the central nervous system, causing paralysis, muscular atrophy, deformation and, in some cases, death.

"India was once thought to be the most difficult country in which to achieve polio eradication," Global Polio Eradication Initiative said in a statement.

Widespread poverty, dense population, poor sanitation, high levels of migration and a weak public health system made the task of reaching out to every child under age five that much more difficult.

Despite India's success against the disease, there are many people for whom the vaccination campaigns have come too late. Polio victims are a common sight on the streets of Indian cities.

Sonu Kumar did not have access to the polio vaccine when he was struck by the disease as a 10-year-old boy.

"My parents were very poor and couldn't afford medical treatment for me," said Kumar, who is paralysed from the waist down. The 24-year-old begs outside a temple in central Delhi and uses a wheelchair to move around.

Some years ago, Kumar saw a TV advertisement by a charity organisation offering free treatment for polio victims in a western Indian city. Doctors who examined him said it was too late for him to get medical help.

For India, the victory against polio is its second major health achievement. In 1980, it succeeded in eliminating smallpox through a sustained immunisation campaign.

An army of nearly 2.5 million volunteers, doctors and medical workers carried out a rigorous campaign across the country to vaccinate children over a period of three years to wipe out the scourge. The number of polio cases came down from 741 in 2009 to 42 in 2010. The last case of polio was reported in eastern India in 2011.

In 2012, the WHO removed India from a list of countries with active endemic wild polio transmission after it passed one year without registering any new cases.

Health officials remained concerned about the possibility of the virus entering the country from neighbouring Pakistan, where a spate of cases has been reported. Indian health authorities have set up polio immunisation booths at the two border crossings with Pakistan and all children who enter by road and train are being given vaccines.

Last month, Delhi announced that travellers from Pakistan would have to show proof that they had been administered the oral polio vaccine at least six weeks before their departure for India. Travellers to India from Kenya also were told to get an additional dose of oral polio vaccine at least six weeks before they departed.

Although polio was eliminated in Kenya in 1984, 10 cases were reported last year mostly in northern Kenya, where there is an influx of refugees.

On Monday India's health ministry was awaiting reports from different parts of the country to come in before making a formal declaration. However, the junior home minister RPN Singh has already tweeted: "Proud day for all of us as Indians … India is polio free for three years."