Israel is among the few countries that practice environmental surveillance for polio, beginning in 1989. Checking designated sites along sewage systems every month for evidence of the virus allows for early detection before there are paralytic cases. For the past decade, the researchers have been trying to trace the origin of the strain that infected two individuals in Central Israel. They tracked the strains to the sewage system, and have been working to pinpoint the origin. Fortunately, because Israel maintains herd immunity for the disease, the wider population has not been threatened.
Dr. Shulman says that in the lab, each strain of the virus can be identified from its genomic structure and traced back to the region from which it originated. "From the sequence of the genome, you can match it with known sequences reported by labs throughout the world," he explains. For example, he and his colleagues traced a wild poliovirus discovered in sewage from the Gaza District to a village in Egypt.
New hope for curing persistent infections
Convinced by the efficacy of Israel's environmental surveillance program, many other countries are starting to develop tracking programs of their own. As a result, they are finding evidence of vaccine-derived polio cases in humans. Paradoxically, Dr. Shulman sees a beacon of hope in these discoveries. As labs across the world report more cases, researchers gain a better understanding of how polioviruses establish persistent infections and can then develop effective measures to eliminate them.
The fellow researchers are now working to develop compounds that can effectively fight these rare cases of persistent poliovirus infections. So far, they have seen promising results, noting that the mutants strains have not become resistant to the drugs under investigation. But for now, Dr. Shulman
|Contact: George Hunka|
American Friends of Tel Aviv University