Characterisation of an echovirus type 11' (prime) epidemic strain causing haemorrhagic syndrome in newborn babies in Hungary

Echovirus 11' (prime) isolates from an epidemic of haemorrhagic syndrome in departments of obstetrics in Hungary have been characterised. The leading component of the clinical disease was carditis and its lethal outcome occurred in 13 newborn babies. Maternal immunity was found to be absent even in women of 41 years of age. The application of monovalent oral poliovirus type 1 vaccine prevented the progress of the epidemic within two weeks. Nevertheless, a serological survey among primovacinees of 3 - 15 months of age revealed that 20% of the babies seroconverted without clinical symptoms during the epidemic. Serological evidence showed that the echovirus 11' infection was unable to interfere with the efficacy of oral poliovirus vaccine (OPV), since seroconversion rates of primovaccinees did not differ significantly from those in the group seroconverted also to echovirus 11' during the vaccination campaign. A 440 nucleotide (nt) fragment of the 5'- non-translated region of 12 epidemic echovirus 11' isolates and 26 echovirus prototype strains was amplified by a nested reverse transcription-polymerase chain reaction (RT-PCR) and analysed using three different restriction endonucleases. The 5'-regions of the echovirus 11' isolates were found to be identical to each other but different from that of the prototype echovirus 11 (Gregory) strain. The results indicate that echovirus 11' isolates underwent genetic changes in the 5'-end and P1 region of the genome before the onset of the epidemic.