ANTIGENIC AND MOLECULAR CHARACTERIZATION OF WILD-TYPE-1 POLIOVIRUS CAUSING OUTBREAKS OF POLIOMYELITIS IN ALBANIA AND NEIGHBORING COUNTRIES IN 1996

Mass vaccination has led poliomyelitis to become a rare disease in a l arge part of the world, including Western Europe. However, in the past 20 years wild polioviruses imported from countries where polio is end emic have been responsible for outbreaks in otherwise polio-free Europ ean countries. We report on the characterization of poliovirus isolate s from a large outbreak of poliomyelitis that occurred in Albania in 1 996 and that also spread to the neighboring countries of Yugoslavia an d Greece. The epidemics involved 145 subjects, mostly young adults, an d caused persisting paralysis in 87 individuals and 16 deaths. The age nt responsible for the outbreak was isolated from 74 patients and was identified as wild type 1 poliovirus by both immunological and molecul ar methods. Sequence analysis of the genome demonstrated the involveme nt of a single virus strain throughout the epidemics, and genotyping a nalysis showed 95% homology of the strain with a wild type 1 polioviru s strain isolated in Pakistan in 1995, Neutralization assays with both human sera and monoclonal antibodies were performed to analyze the an tigenic structure of the epidemic strain, suggesting its peculiar anti genic characteristics. The presented data underline the current risks of outbreaks due to imported wild poliovirus and emphasize the need to improve vaccination efforts and also the need to implement surveillan ce id countries free of indigenous wild poliovirus.