Threatwatch is your early warning system for global dangers, from nuclear peril to deadly viral outbreaks. Debora MacKenzie highlights the threats to civilisation – and suggests solutions
The outbreak of polio in Syria may carry a major risk to
Threatwatch is your early warning system for global dangers, from nuclear peril to deadly viral outbreaks. Debora MacKenzie highlights the threats to civilisation – and suggests solutions
The outbreak of polio in Syria may carry a major risk to Europe, epidemiologists in Germany warned on Friday. Paradoxically, this is because Europe has moved to using a safer vaccine that is crucial to the goal of global polio eradication.
Other epidemiologists argue, however, that Europe and other regions are at no greater risk than before, if a massive vaccination campaign kicking off now stops polio re-establishing itself across the Middle East. If that fails, though, there may be a double peril: polio virus will be more widespread, and there may not be enough vaccine to contain it.
Ten cases of polio have now been confirmed in Syria, where vaccination efforts have collapsed during two years of civil war. Most victims are under two years old. Because polio paralyses only one in 200 unimmunised people infected, that means many more people are carrying and spreading the virus.
The situation is made all the worse because polio is spread in faeces, and sanitation, especially for the more than four million refugees within Syria, is overstrained and damaged by fighting.
Martin Eichner of the University of Tübingen and Stefan Brockmann of the regional public health office in Reutlingen, both in Germany, warned in The Lancet that Europe is at risk from this outbreak.
In countries where polio virus either still circulates or there is a strong risk of its reintroduction, children get oral polio vaccine (OPV) containing a live, weakened virus. This replicates in the gut, inducing powerful immunity which both protects the child from disease and stops them spreading any polio virus they may encounter.
The problem with the oral vaccine is that in one in 2.7 million cases, the live virus can revert and cause paralysis – and can continue to circulate. For this reason, the Global Polio Eradication Initiative plans to switch the whole world to a killed version of the vaccine as polio disappears. Rich countries, where the risk of the vaccine exceeds the risk of encountering polio, have already done so. No country in the European Union has used the oral vaccine since 2010, some for much longer.
Killed vaccine, however, doesn’t induce the same powerful gut i