Public health officials stand poised to eliminate polio from the planet. But a new study shows that the job won't be over when the last case of the horrible paralytic disease is recorded.

Using disease-transmission models, University of Michigan graduate research fellow Micaela Martinez-Bakker and two colleagues demonstrate that silent transmission of poliovirus could continue for more than three years with no reported cases.

To ensure that the disease is truly eradicated, aggressive surveillance programs and vaccination campaigns must continue in endemic countries for years after the last reported case, they conclude.

"Using transmission models, we show that you can have sustained chains of silent transmission in populations for more than three years, without a single person ever showing up as a reported polio case," said Martinez-Bakker, who completed the six-year polio study as part of her doctoral dissertation in the U-M Department of Ecology and Evolutionary Biology.

"Once we've eradicated polio – or think we've eradicated polio – we probably should intensify the environmental surveillance to make sure the virus is not just lurking under the hood at very low levels," she said. "Polio eradication is about eradicating the virus. It's not about eradicating the disease paralytic polio."

The new findings were published June 19 in the open access journal PLOS Biology in a study titled "Unraveling the Transmission Ecology of Polio." The co-authors are Martinez-Bakker's dissertation advisers, Professors Aaron King and Pejman Rohani of the U-M Department of Ecology and Evolutionary Biology.

Michigan News press release