Is polio in our sewage as worrying as it sounds?

Last week, public health officials declared a ‘national incident’
after they found vaccine-derived poliovirus in London sewage
samples. No cases of polio symptoms have been reported but there is
evidence the virus is spreading. So what does it mean to have found
the virus almost 20 years after the UK was declared polio-free? Ian
Sample speaks to epidemiologist Nicholas Grassly to find out how
worried we should be and what it means for the global effort to
eradicate polio.. Help support our independent journalism at
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