Enteroviral Infection Outbreak in the Republic of Belarus: Principal Characteristics and Phylogenetic Analysis of Etiological Agents

For the last decade enterovirus outbreaks were registered in all of six districts of Belarus. Two of them, reported in 1997 (in Gomel) and in 2003 (in Minsk), were the most extensive and involved 461 and 1,351 patients respectively. Virus ECHO 30 was identified as the dominant etiologic agent of the outbreak in 1997 whereas co-circulation of ECHO 30, ECHO 6 and Coxsackievirus B5 took place in 2003. Analysis of clinical manifestations during the Minsk outbreak revealed unusually high rate of severe clinical forms of infection including aseptic meningitis, encephalitis and myocardial disorders. Epidemiologic observation was ordinary for enterovirus epidemics in temperate climates: the peak of the outbreak was recorded during summer-autumn period of 2003, and 0-14 years old children predominated. Data from the case-control study indicated that illness was associated with drinking water from community water system. Also the laboratory examination demonstrated contamination of different water samples with the epidemic virus serotypes and sequence analysis showed high level of genetic similarity between waterborne and clinical isolates. For these reasons the outbreak should be classified as a waterborne one. Phylogenetic reconstruction showed that all Belarusian ECHO 30 isolates belong to the major genotype of ECHO 30 which has been circulating for last 15 years in Europe and North America. Viral agents of 2003 were very similar and substantially differed from isolates of 1997. Comparison of nucleotide sequences of isolates from myocarditis patients revealed their considerable genetic similarity with ECHO 30 isolates from patients with aseptic meningitis and from water. The results of the study draw attention to the importance of virological control of tap and bottled water as a relevant measure aimed at reduction of epidemiological risks.