A POLIO outbreak in Haiti and the Dominican Republic two years ago was caused by mutant forms of the virus used in polio vaccine that might have acquired the ability to spread from person to person by swapping genes with viruses in the gut.
The weakened form of the polio virus used in the oral vaccine has about 50 changes in its RNA compared with the original virus, making it less dangerous and less likely to spread. It’s known that a few random reversals of these changes can make it deadly again.
But the latest study raises the frightening possibility…
