Aseptic meningitis outbreak caused by echovirus 30 in two regions in Bulgaria, May-August 2012.

An aseptic meningitis outbreak emerged in two regions in Bulgaria in 2012 and echovirus 30 (E30) was established as the aetiological agent by cell culture isolation, serological test, and molecular-based techniques. A total of 157 patients with aseptic meningitis were investigated, of which 117 were confirmed as having E30-associated disease. Molecular analysis of 12 E30 isolates revealed 99-100% nucleotide and amino-acid identity between them and a close correlation with a Greek strain involved in an E30 outbreak in 2012. Children aged 5-14 years were mainly affected, which could reflect the absence of E30 epidemics in Bulgaria for a period of 11 years. The first case with E30 isolation (a 2-year-old patient from Plovdiv) was notified at the end of April 2012. This was most likely the index case, from which the spread of the virus started, causing sporadic cases first, which later led to an aseptic meningitis outbreak facilitated by person-to-person viral transmission.