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A review of recent publications on epidemiology and seroepidemiology of enterovirus type 71 in various regions of the world and authors' own results of study of seroepidemiology and molecular epidemiology of EV71 in Russia are presented.

6 year molecular-biological monitoring of enteroviruses in the Far East and Zabaikalye was carried out. Nucleotide sequence of 125 strains was determined from 2006 to 2011. Molecular analysis was carried out in VP1 virus genome region. Phylogenetic interactions for ECHO-6, ECHO-30, ECHO-11, Coxsackie B-5 (CB-5), Coxsackie B-1 (CB-1) and Coxsackie A-9 (CA-9) were analyzed. Highly dynamic epidemiology was shown to be inherent for ECHO-6 and ECHO-30 viruses and is characterized by genetic heterogeneity and consequent change of virus variants. On the contrary a relative stability of circulating genotypes is intrinsic for CB-1, CB-5 and ECHO-11 enteroviruses. The results of molecular-biological studies indicate frequent introduction of new enterovirus variants from countries of Europe and Asia.

Aim: Evaluate the effectiveness of multiplex reverse transcription (RT) and polymerase chain reaction with fluorescence detection in real time mode (qPCR) methods for differential detection of 11 groups of intestine viruses (adenoviruses, enteroviruses, polioviruses, hepatitis A and E viruses, group A and C rotaviruses, orthoreoviruses, noroviruses, sapoviruses and astroviruses) in various biological samples., Materials and Methods: Panels of virus isolates and clinical samples characterized by reference methods were used to evaluate sensitivity of detection of various intestine viruses. Nucleic acids were isolated from study samples and multiplex RT and qPCR were carried out., Results: Sensitivity of laboratory reagent kit (LRK) when compared with results obtained from reference methods was 100% for rotavirus A, adenovirus, enterovirus and norovirus, 88.9% for hepatitis E virus and 92.3% for hepatitis A virus, and diagnostic specificity - 99.4%. During analysis of 697 clinical samples from patients with acute intestine infection symptoms nucleic acids of various intestine viruses were isolated in 71.7%., Conclusion: Multiplex qRT-PCR was shown as an effective method of etiologic diagnostics of an intestine viral infection. Use of LRK was demonstrated to establish etiology of intestine diseases in 63 - 72% and in children with watery diarrhea - in approximately 90% of cases.

Enterovirus type 71 (EV71) is a causative agent of large outbreaks of hand, foot, and mouth disease (HFMD) in Europe (Bulgaria, 1975; Hungary, 1978) and South-East Asia (Malaysia, 1977; Taiwan, 1998; Singapore, 2000-2007; People's Republic of China, 2007-2009). HFMD afflicted children less than 10 years of age and resulted in recovery within 3-7 days. In a small percentage of infants (aged 6 months to 3 years), HFMD was accompanied by acute neurological complications, such as serous meningitis, poliomyelitis-like syndrome (extremity pareses and muscle paralyses); brain stem encephalitis (myoclonic jerks, tremor, lethargy, swallowing and speech disorders, cardiopulmonary failure, pulmonary edema, shock, coma, death). X-ray study revealed pulmonary hemorrhages and edema. Mortality rates were as high as 82-94% in severe cases. Incapacitating motor, respiratory, and psychoemotional disorders persisted in some surviving children. Pathomorphologically, patients with central nervous system disease and cardiopulmonary failure were found to have acute inflammation of the grey matter of the brain stem (medulla oblongata, pons) and spinal cord. Inflammatory changes in the lung and myocardial tissues were negligible or absent. Fatal pulmonary edema was neurogenic in origin and resulted from damage to the respiratory and vasomotor centers of the brain stem.

Human enteroviruses comprised by more than 100 serotypes, they spread everywhere and can cause wide spectrum of diseases as well as significant social and economic loss. Influenza-like illness and mild forms of enterovirus infection (herpangina, exanthema) are widespread and causes of significant number of visits in clinics. Economic cost of mild form of enterovirus infection is not high although great number of cases (10 - 15 mln cases yearly in USA) determines its important economic significance. Single cases and outbreaks of enterovirus aseptic meningitis occur less frequently but lead to significant economic burden due to hospitalization costs. Enteroviruses are also cause up to 30% of sepsis-like disease in newborns and play important role in infant morbidity and mortality. Potential of enteroviruses as a source of new diseases in humans has a special significance for practical healthcare. In XX century enteroviruses became a cause of pandemics of paralytic poliomyelitis, hemorrhagic conjunctivitis, and foot-and-mouth-like disease, which caused vast social and economic loss, and emergence of new forms of enterovirus infection is quite possible in XXI century.

In 1970s enterovirus type 71 (EV71) caused several epidemics of poliomyelitis-like disease with severe neurologic sequelae. In the last 20 years EV71 was the cause of series of outbreaks and epidemics of foot-and-mouth disease-like conditions with neurologic sequelae in countries of South-East Asia. During the last epidemic of EV71 infection, which occurred in China in 2008, more than 60,000 cases was registered, 38 of which were lethal. Some aspects of epidemiology and laboratory diagnostics of disease caused by EV71 are considered in this review.

A total of 3194 cases of enterovirus meningitis were notified in the Russian Federation in 2005, of them there were 1434 cases in the Khabarovsk Territory. Enteroviruses were isolated from 1020 out of the virologically studied 1362 patients from the Khabarovsk Territory. Viruses E6 and E30 were isolated in 80 and 14.7% of cases, respectively. E1, E3, E7, E33, Coxsackie virus B1, B4, B5, and A10 were sporadically detected. The E6 strains isolated in Komsomolsk-on-Amur were identical while E6 strains isolated in Khabarovsk belonged to two different genotypes and greatly differed from those isolated in Konsomolsk-on-Amur. The virus E30 strains isolated in Khabarovsk and Komsomolsk-on-Amur had a 1% difference in VP1 genome nucleotide sequence and belonged to E30 subtype that circulated in Russia and Kazakhstan in 2004-2005.

Results of epidemiologic, virologic, and serologic studies of enterovirus infections in Khabarovsk region from 1975 to 2006 were analyzed. Patterns of epidemic process of these infections were established: periodic change of dominating type of pathogen in the population; onset of the large epidemic peaks of incidence during emergence of circulation of new for the given area serotypes of enteroviruses; possibility of realization of several routes of virus transmission. Role of water factor in the progress of the epidemic process was revealed. Etiology of the large epidemic rise of aseptic meningitis incidence in Khabarovsk region in 2006 was established--the leading pathogens were ECHO viruses serotypes E6 and E30.

Enterovirus uveitis (EU) is a new infant eye disease that was first detected and identified in Russia in 1980-1981. Three subtypes of human echoviruses (EV19K, EV11A, and EV11/B) caused 5 nosocomial outbreaks of EU in different Siberian cities and towns in 1980-1989, by affecting more than 750 children mainly below one year of age. Sporadic and focal EU cases (more than 200) were also retrospectively diagnosed in other regions of Russia and in different countries of the former Soviet Union. There were following clinical manifestations: common symptoms of the infection; acute uveitis (rapid focal iridic destruction, pupillary deformities, formation of membranes in the anterior chamber of the eye); and in 15-30% of cases severe complications, cataract, glaucoma, vision impairments. Uveitis strains EV19 and EV11 caused significant uveitis in primates after inoculation into the anterior chamber of the eye, as well as sepsis-like fatal disease with liver necrosis after venous infection. The uveitis strains are phylogenetically and pathogenetically close for primates to strains EV19 and EV11 isolated from young children with sepsis-like disease. The contents of this review have been published in the Reviews in Medical Virology, 2004, vol. 14, p. 241-254.

Enteroviruses, members of the family Picornaviridae (more than 70 serotypes), are distributed throughout the world and cause a broad spectrum of clinical manifestations in man and animals. Human enteroviruses are classified into 5 species: human enteroviruses A to D, and Poliovirus. Recombination has long been known to be an important property of poliovirus genetics; however, recombination has been recently shown to be also ubiquitous in non-polio enteroviruses. Prototype enterovirus strains have complex phylogenetic relations and all currently available enterovirus strains are recombinant to prototype strains. The extremely high rate of recombination allows the fragments of the enterovirus genome to evolve independently at a microevolutionary scale. Recombination strictly takes place between the members of the same species, usually outside the capsid-encoding genome region. Therefore, it can be concluded that the species enterovirus exists as a worldwide reservoir of the genetic information that shuffles frequently to produce new virus variants. This new model of the genetics of enterovirus accounts for failures to associate the serotype of enteroviruses and the form of the disease caused. The contents of this review have been published in the Reviews in Medical Virology, 2005.

Nucleotide sequences of the VP1 genome of 28 ECHO 30 strains isolated in 1998-2002 in Russia and several CIS countries were determined. The EV30 studies strain were divided into 4 groups according to isolation place and time. Group 1 is presented by 2 strains isolated in 1998 in Russia and Byelorussia. Group 2 comprises 17 strains isolated in 1999-2000 in Russia (its southern regions and Stavropol Territory), Ukraine, Georgia, and Azerbaijan. Five strains isolated in 2002 in Russia (Kalmykia) belong to Group 3; and Group 4 has 4 strains isolated in 2002 in Moldova and Russia (Magadan). A frequently changing EV30 subtype was simultaneously detected in extensive territories.

Follow-up (5.5 years) of monkeys with a history of acute enterovirus uveitis (AEU) after intraocular infection with ophthalmotropic ECHO 11 and ECHO 19 strains showed progressive changes in the infected eye; destruction of the iris, formation of films in the anterior chamber of the eye, deformation of the pupil, and signs of cataract and glaucoma. A short (1-30 days) stage of active reproduction of infective virus (up to 10(10) TCD50/g tissue in the first days postinfection) was followed by the second very long stage of limited specific multiplication of virus in ocular tissues. The virus was not detected during the second stage, but its components (virusspecific antigen and crystalloid accumulations of virions) were found in ophthalmic and conjunctival tissues; moreover, high levels of neutralizing antibodies were detected in the blood. The results indicate AEU transformed into a stubborn persistent infection of the eye in monkeys. The findings of this follow-up and published reports about many-year follow-up of children with AEU permit us to classify a post-uveitis disease as a special nosological form of a persistent enterovirus infection and denote it as enterovirus post-uveitis syndrome. The main signs of this syndrome are a history of AEU, progressive destructive changes in the anterior segment of the eye, presence of virus components in ocular tissues in remote periods after infection, and high antibody level in the blood.

The authors studied the phenomenon of superhigh virulence for monkeys of viruses ECHO 11 (E11) and ECHO 19 (E19) isolated in 1981-1991 in Russia and Tadzhikistan from children with acute enterovirus uveitis or severe enterovirus infection. In 21 morphologically examined animals after coma, macrofocal or total necrosis of hepatocytes in weak inflammation was seen as early as experiment day 1-6. Hepatic lesion interpreted as hepatosis underlies acute hepatic failure with lethal outcome. The most intensive reproduction of viruses E11 and E19 occurred in the liver. Changes in the kidneys, lungs, spleen, adrenals, CNS detected in many animals aggravated the disease, but were not the primary cause of death. The disease in monkey was similar by the main criteria to superacute lethal diseases (acute hepatic failure against massive hepatic necrosis, hemorrhagic syndrome) registered in outbreaks of E11 and E19-virus infection in children in the USA, Great Britain, Israel, Russia and Ukraine. Monkeys can be used as man-adequate model for study of enterovirus superacute lethal necrosis of the liver.