whether a disease is still present in a given area (and, therefore,
that further prevention efforts are needed) is a critical
part of any disease eradication effort. The WHO Global Polio
Laboratory Network uses molecular techniques to determine
whether wild-type polio is circulating in areas undergoing
eradication efforts. Since the worldwide campaign began, cases
of polio have declined by 99% (from 350,000 cases to less
than 3,000), and the number of countries in which polio is
endemic has decreased from 125 to 20.
began training Network virologists in 1986, soon after the
Pan American Health Organization declared its goal of eliminating
polio from the Americas. CDC will continue to train Network
virologists for several more years, as new diagnostic methods
are developed to meet the stringent surveillance criteria
necessary to obtain certification of global polio eradication.