The murder of nine female health workers involved in child immunisation on February 8 in Kano (the largest city in northern Nigeria) is a chilling reminder that saving children’s lives is not a goal shared by everyone. Unless such incidents are effectively prevented in countries where the poliomyelitis (‘polio’) virus still circulates, vaccination campaigns may collapse and the world may fail to eradicate this virus that causes lifelong paralysis or death.

The incident follows the murder in Pakistan of nine volunteer vaccinators (mostly women) late last year, and seven clinic workers on new year’s day. Those murders were well-planned – four of the volunteers were shot within 20 minutes in various parts of Karachi, the country’s largest city. The killings took place during a nationwide campaign to vaccinate 5.2 million children against polio.

It’s not yet clear whether the Nigerian murders were aimed specifically at the polio program given the national vaccination campaign ended on February 5. The murdered women were in the mop-up phase of vaccination, trying to immunise children who had been missed.

Smallpox is the only human disease that we’ve completely eradicated but we stand tantalisingly close to making polio the second. Nigeria, Pakistan, and Afghanistan are the only three countries in the world that have never interrupted polio transmission. In 1988, polio infection paralysed or killed 350,000 people, mainly children. Following a global eradication initiative, that number had fallen to just 222 cases last year in five countries – Nigeria (121 cases), Pakistan (58), Afghanistan (37), Chad (five), and Niger (one).

For every person paralysed or killed by polio, however, another 99 are infected who have only mild or no symptoms but can spread polio to others. This is why it’s important to vaccinate close to 100% of all children to stamp out the virus (and it’s why the campaign had a mop-up phase).

Polio is not a “tropical” disease – cases were still occurring in Australia in the 1960s. In 1952, there were 58,000 cases of paralytic polio in the United States, resulting in more than 3,000 deaths and 22,000 people left with varying degrees of paralysis.

While no-one has claimed responsibility for the killings in Nigeria, the most likely suspect is the radical Islamist group Boko Haram, which has attacked churches, government offices and police stations in the north of the country.

There’s a history of opposition to polio vaccination by certain Muslim clerics. Between 2002 and 2005, religious leaders forced the cessation of the vaccination campaign in northern Nigeria claiming the vaccines were part of a western plot to sterilise young girls and eliminate the Muslim population. As a result of the subsequent epidemic, polio was exported to 17 countries that had been polio-free.

The Abuja Declaration signed by the Nigerian president and all state governors in February 2009 signalled the start of a renewed effort for polio eradication in the country. The number of reported cases declined dramatically in the following years and the last case was reported on December 3, 2012.

In Pakistan, there has been opposition to immunisation drives in parts of the country, particularly after a fake CIA hepatitis vaccination campaign that helped to locate Osama Bin Laden in 2011.

In July 2012, the Taliban commander Hafiz Gul Bahadur issued a fatwa forbidding the vaccination of more than 200,000 children in north and south Waziristan in the country’s northwest. He was convinced that spies under the guise of medical staff would enter these areas to monitor the activities of Islamic militants.

Despite these challenges, high-level political commitment has led to significant progress in Pakistan. Polio cases dropped from 198 in 2011 to just 58 in 2012. But that progress is now threatened by the murder of polio volunteers.

The vaccination campaign was suspended in Karachi, a city of 18 million people, and as one Pakistani official told the BBC News:

Many of the roughly 80,000 field workers across Pakistan, however needy they may be, will be forced to ask themselves whether the 1,500 rupee ($15) fee they will receive for a three-day campaign is worth the risk.

In the age of fast and easy global travel, a resurgence of polio in Nigeria and Pakistan poses a threat to the entire world. The last case of polio reported in Australia was in a Pakistani student. And Nigeria has a history of exporting polio to its impoverished neighbours. In many countries that eliminated polio decades ago, vaccination rates have dropped and immunity levels are low.

Eliminating polio from its remaining reservoirs in Afghanistan, Nigeria and Pakistan may require a concerted diplomatic effort by countries with large Muslim populations, such as Indonesia and Egypt. At the 2011 Commonwealth Heads of Government meeting, the Australian government played a leading role in mobilising more than $100 million in funding for polio eradication.

Australia can also play a leading role in advocacy and use its seat in the UN Security Council to support whatever measures are needed to ensure that children in Nigeria, Afghanistan, and Pakistan are protected from this disease. By doing so, they will avert a global public health emergency, and seize the opportunity to finish the job of eradicating polio.