During the twentieth century, poliomyelitis (‘polio’) crippled thousands of people – mostly children – making it one of the most feared diseases of the modern era. Caused by poliovirus, the acute infection can, following entry into the central nervous system in about one per cent of cases, lead to irreversible destruction of motor neurons and paralysis. There is currently no treatment for polio, and the only method of control is vaccination. However, the available vaccines are highly effective, and the disease was targeted for eradication by global vaccination in 1988.

Like smallpox, which was officially eradicated in 1979, polio has a number of characteristics that makes this a possibility. Crucially, the virus can only survive and replicate in human hosts and lacks an animal reservoir: once all susceptible individuals are vaccinated, the disease will be effectively eradicated. A lack of chronic or latent infection, coupled with an easily recognised presentation of the disease, also aid targeted vaccination in susceptible populations.

The Global Polio Eradication Initiative (GPEI) decreased the number of global polio cases from an estimated 350,000 in 1988 to 223 reported cases in 2012. The disease is now endemic only to Afghanistan, Nigeria and Pakistan (compared with 125 countries in 1988). However, 2013 saw a resurgence of polio in Africa and the Middle East. A mixture of war and politics has seriously hindered efforts at vaccinating whole populations, with the former contributing greatly to the dramatic increase in the number of cases in previously non-endemic countries. 

War has always been a fertile breeding ground for infectious disease, and the ongoing conflict in Syria – where seventeen cases of polio, the first in the country since 1999, were reported in 2013 – has demonstrated just how easily the loss of infrastructure promote the spread of infection. Disruption of transport routes continues to limit World Health Organisation (WHO) intervention, and as the main form of the polio vaccine is live and requires cold storage to remain potent, the intermittent loss of power in the country can render large stocks of the vaccine ineffective. Overcrowding and poor sanitation play major roles in promoting viral spread, particularly since poliovirus is transmitted through the faeco-oral route. Continued conflict runs the risk of endemic disease re-emerging in Syria and the spreading to neighbouring countries via refugees. The fear is that the Syrian conflict will provide a new foothold for polio in the Middle East.

Politics has a more subtle ability to influence the success of local vaccination programmes. War involves a breakdown of trust, and intervention by external agencies like the WHO or UNICEF may be viewed with suspicion. However, this is not just limited to violent conflict. In Nigeria, a country previously free of polio, religious officials have opposed polio vaccination as a US government and UN conspiracy to sterilise Muslims. Violence has resulted, with nine health workers shot dead in Kano in 2013. In Pakistan, legitimate vaccination drives have been hindered by reports that the CIA has used fake vaccination programmes to collect civilian DNA as part of military profiling. The WHO has attempted to negotiate vaccination ceasefires and foster greater trust with governments, but political opposition continues to enable endemic disease in such nations.

It is no longer our scientific understanding that is limiting eradication programmes. Rather, factors such as war and politics are now the largest obstacles to be overcome. The drive for polio eradication has reached a critical point. Widespread vaccination could see effective eradication within the next few years, but at present the virus is on the brink of a resurgence which, if unchecked, will be difficult to reverse.