Genomic characterization of human and environmental polioviruses isolated in Albania

Between April and December 1996, a serious outbreak of poliomyelitis occurr ed in Albania; almost 140 subjects were involved, and the episode presented an unusually high mortality rate (12%). During the outbreak, water samples from the Lana River in Tirana, Albania, and stool samples from two cases o f paralytic poliomyelitis were collected and analyzed for the presence of p olioviruses. Six polioviruses were isolated from the environmental and huma n samples, according to standard methods. All the samples were characterize d by partial genomic sequencing of 330 bases across the 5' untranslated reg ion (5'-UTR) (nucleotide positions 200 to 530) and of 300 bases across the VP1 region (nucleotide positions 2474 to 2774). Comparison of these sequenc es with those present in data banks permitted the identification of environ mental isolates Lana A and Lana B as, respectively, a Sabin-like type 2 pol iovirus and an intertypic recombinant poliovirus (Sabin-like type 2/wild ty pe 1), both bearing a G instead of an A at nucleotide position 481. The two other environmental polioviruses were similar to the isolates from the par alytic cases. They were characterized by a peculiar 5'-UTR and by a VPI reg ion showing 98% homology with the Albanian epidemic type 1 isolates reporte d by other authors. This study confirms the environmental circulation in Al bania of recombinant poliovirus strains, likely sustained by a massive vacc ination effort and by the presence in the environment of a type 1 polioviru s, as isolated from the Lana River in Tirana about 2 months before the firs t case of symptomatic acute flaccid paralysis was reported in this town.