Epidemiological and etiological aspects of enterovirus infection in Russia and Vietnam

The epidemic situation and etiological factors of enterovirus infection in Russia and Vietnam were analysed and compared. The identified strains of enteroviruses of 47 types, which circulated in Russia in 2018–2019, belonged to different species: Enterovirus species A (CV-A2, CV-A4, CV-A6, CV-A8, CV-A10, CV-A16, EV-A71), as well as Enterovirus species B and Enterovirus species C. The strains isolated from 87 children from southern Vietnam hospitalised in 2018–2019 into infectious hospitals while having enterovirus infection with exanthema were also studied. All identified strains were represented by Enterovirus species A: EV-A71 — 59 strains, CV-A10 — 20 strains, CV-A16 — 5 strains, CV-A6 — two strains and CV-A2 — one strain. Out of 59 viruses EV-A71, 53 strains belonged to genotype C4 and 6 strains belonged to genotype B5. The sequences of EV-A71 strains of genotype C4 from South Vietnam formed a monophyletic cluster with the sequences of EV-A71 viruses which circulated during 2016–2018 in different provinces of China, and they were very close to EV-A71 strains of the same genotype from the Yunnan Province. These strains were genetically different from Russian viruses and Vietnamese viruses identified in the years 2003–2005 and 2011– 2012. Most of the cases of enterovirus infection from southern Vietnam (78%) caused by EV-A71 virus of genotype C4 were reported in three provinces located in southern Vietnam in the Mekong Delta. The epidemic process and the etiology of enterovirus infection in Russia and Vietnam have common features. At the same time, the epidemic situation in these countries is not the same. The incidence of enterovirus infection is influenced by geographic, climatic, economic and demographic factors that differ in two countries. In the majority of territories of Russia, the climate is temperate or cold, seasonal rises in the incidence rates of enterovirus infection usually occur in the summer, when people go on vacation, spend a lot of time outdoors and swim in open reservoirs. In Vietnam, a constant high-level temperature, a high population density and a large proportion of children determine the higher incidence of enterovirus infection, especially in the southern provinces of Vietnam, compared to Russia. The fact that more than 20% of the Vietnamese population lives in the Mekong Delta, which is the largest river in Indochina, has a significant impact on the epidemic process of enterovirus infection in South Vietnam. The Mekong River which flows through China, Laos, Thailand, Cambodia and Vietnam, and carries huge streams of water, including rainstorm waters and sewages, from all of these countries into the southern provinces of Vietnam, which have the highest incidence rates of enterovirus infection in the country. The results of the research underline the importance of active epidemiological and virological surveillance of enterovirus infection, which plays the key role in informing the public health authorities about the changes in the epidemic situation in order to take appropriate measures and develop the prevention strategies. The goal of anti-epidemic and preventive measures is to reduce the incidence of enterovirus infection and the economic burden of this infection for Russia and Vietnam.