An emerging recombinant human enterovirus 71 responsible for the 2008 outbreak of hand foot and mouth disease in Fuyang city of China.

Hand, foot and mouth disease (HFMD), a common contagious disease that usually affects children, is normally mild but can have life-threatening manifestations. It can be caused by enteroviruses, particularly Coxsackieviruses and human enterovirus 71 (HEV71) with highly variable clinical manifestations. In the spring of 2008, a large, unprecedented HFMD outbreak in Fuyang city of Anhui province in the central part of southeastern China resulted in a high aggregation of fatal cases. In this study, epidemiologic and clinical investigations, laboratory testing, and genetic analyses were performed to identify the causal pathogen of the outbreak. Of the 6,049 cases reported between 1 March and 9 May of 2008, 3023 (50%) were hospitalized, 353 (5.8%) were severe and 22 (0.36%) were fatal. HEV71 was confirmed as the etiological pathogen of the outbreak. Phylogenetic analyses of entire VP1 capsid protein sequence of 45 Fuyang HEV71 isolates showed that they belong to C4a cluster of the C4 subgenotype. In addition, genetic recombinations were found in the 3D region (RNA-dependent RNA polymerase, a major component of the viral replication complex of the genome) between the Fuyang HEV71 strain and Coxsackievirus A16 (CV-A16), resulting in a recombination virus. In conclusion, an emerging recombinant HEV71 was responsible for the HFMD outbreak in Fuyang City of China, 2008.

The development and application of the two real-time RT-PCR assays to detect the pathogen of HFMD.

Large-scale Hand, Foot, and Mouth Disease (HFMD) outbreaks have frequently occurred in China since 2008, affecting more than one million children and causing several hundred children deaths every year. The pathogens of HFMD are mainly human enteroviruses (HEVs). Among them, human enterovirus 71 (HEV71) and coxsackievirus A16 (CVA16) are the most common pathogens of HFMD. However, other HEVs could also cause HFMD. To rapidly detect HEV71 and CVA16, and ensure detection of all HEVs causing HFMD, two real-time hybridization probe-based RT-PCR assays were developed in this study. One is a multiplex real-time RT-PCR assay, which was developed to detect and differentiate HEV71 specifically from CVA16 directly from clinical specimens within 1-2 h, and the other is a broad-spectrum real-time RT-PCR assay, which targeted almost all HEVs. The experiments confirmed that the two assays have high sensitivity and specificity, and the sensitivity was up to 0.1 TCID50/ml for detection of HEVs, HEV71, and CVA16, respectively. A total of 213 clinical specimens were simultaneously detected by three kinds of assays, including the two real-time RT-PCR assays, direct conventional RT-PCR assay, and virus isolation assay on human rhabdomyosarcoma cells (RD cells). The total positive rate of both HEV71 and CVA16 was 69.48% with real-time RT-PCR assay, 47.42% with RT-PCR assay, and 34.58% with virus isolation assay. One HFMD clinical specimen was positive for HEV, but negative for HEV71 or CVA16, which was identified as Echovirus 11 (Echo11) by virus isolation, RT-PCR, and sequencing for the VP1 gene. The two real-time RT-PCR assays had been applied in 31 provincial HFMD labs to detect the pathogens of HFMD, which has contributed to the rapid identification of the pathogens in the early stages of HFMD outbreaks, and helped to clarify the etiologic agents of HFMD in China.

[Epidemiology and etiology of hand-foot-and-mouth disease in Hainan, 2010].

To reveal the epidemiological and pathogenic characteristics of Hand-foot-and-mouth disease (HFMD) in Hainan province in 2010, epidemiology data of HFMD reporting cases were analyzed, clinical specimens from 1346 HFMD cases were collected for enterovirus (EV) detection. Viral isolation was performed for EV nucleic acid positive samples. Complete VP1 encoding region of EV71 were sequenced and analyzed with Sequencher (version 5.0) and MEGA software (version 5.0). The epidemiology data showed that all 18 prefectures in Hainan had reporting cases during 2010, with higher incidence in the northeast; and the children less than 4 years old accounted for the majority of the suffered; the epidemic reached peak during September to October, which was different from other Provinces in China. The laboratory results indicated that EV71 and CA16 were identified as the major causative pathogens in Hainan in 2010, however, EV71 infection was absolutely dominant among severe and fatal cases. In addition, some HFMD cases were identified associated with other serotypes of EV infections. Molecular epidemiological analysis showed that all the EV71 strains belonged to C4a evolutionary branch, which is the dominant evolutionary branch in China in recent years, and at least three transmission chains existed. This study has an important information in clarifying the characteristics of epidemics and transmission of HFMD in Hainan, and to provide the guidance for HFMD prevention and control in the future.

Complete genome analysis of the C4 subgenotype strains of enterovirus 71: predominant recombination C4 viruses persistently circulating in China for 14 years.

Genetic recombination is a well-known phenomenon for enteroviruses. To investigate the genetic characterization and the potential recombination of enterovirus 71 (EV71) circulating in China, we determined the 16 complete genome sequences of EV71 isolated from Hand Foot Mouth Disease (HFMD) patients during the large scale outbreak and non-outbreak years since 1998 in China. The full length genome sequences of 16 Chinese EV71 in present study were aligned with 186 genome sequences of EV71 available from GenBank, including 104 China mainland and 82 international sequences, covering the time period of 1970-2011. The oldest strains of each subgenotype of EV71 and prototype strains of HEV-A were included to do the phylogenetic and Simplot analysis. Phylogenetic analysis indicated that all Chinese strains were clustered into C4 subgenotype of EV71, except for HuB/CHN/2009 clustered into A and Xiamen/CHN/2009 clustered into B5 subgenotype. Most of C4 EV71 were clustered into 2 predominant evolutionary branches: C4b and C4a evolutionary brunches. Our comprehensive recombination analysis showed the evidence of genome recombination of subgenotype C4 (including C4a and C4b) sequences between structural genes from genotype C EV71 and non-structural genes from the prototype strains of CAV16, 14 and 4, but the evidence of intratypic recombination between C4 strains and B subgenotype was not enough strong. This intertypic recombination C4 viruses were first seen in 1998 and became the predominant endemic viruses circulating in China mainland for at least 14 years. A shift between C4a and C4b evolutionary brunches of C4 recombination viruses were observed, and C4a viruses have been associated with large scale nationwide HFMD outbreak with higher morbidity and mortality since 2007.

The persistent circulation of enterovirus 71 in People's Republic of China: causing emerging nationwide epidemics since 2008.

Emerging epidemics of hand-foot-and-mouth disease (HFMD) associated with enterovirus 71 (EV71) has become a serious concern in mainland China. It caused 126 and 353 fatalities in 2008 and 2009, respectively. The epidemiologic and pathogenic data of the outbreak collected from national laboratory network and notifiable disease surveillance system. To understand the virological evolution of this emerging outbreak, 326 VP1 gene sequences of EV71 detected in China from 1987 to 2009 were collected for genetic analyses. Evidence from both traditional and molecular epidemiology confirmed that the recent HFMD outbreak was an emerging one caused by EV71 of subgenotype C4. This emerging HFMD outbreak is associated with EV71 of subgenotype C4, circulating persistently in mainland China since 1998, but not attributed to the importation of new genotype. Originating from 1992, subgenotype C4 has been the predominant genotype since 1998 in mainland China, with an evolutionary rate of 4.6∼4.8×10⁻³ nucleotide substitutions/site/year. The phylogenetic analysis revealed that the majority of the virus during this epidemic was the most recent descendant of subgenotype C4 (clade C4a). It suggests that the evolution might be one of the potential reasons for this native virus to cause the emerging outbreak in China. However, strong negative selective pressure on VP1 protein of EV71 suggested that immune escape might not be the evolving strategy of EV71, predicting a light future for vaccine development. Nonetheless, long-term antigenic and genetic surveillance is still necessary for further understanding.

[Analysis on genetic character of coxsackievirus A16 strains isolated in Shanghai in 2002].

OBJECTIVE: To reveal the genetic characteristic of Coxsackie virus A16 (CVA16) strains isolated during an epidemic of Hand-Foot-Mouth Disease (HFMD) in Shanghai in 2002. METHODS: CVA16 strains were isolated from the patients of HFMD during the epidemic in Shanghai in 2002. The VP1 coding gene of CVA16 strains was amplified by reverse transcription-polymerase chain reaction (RT-PCR) and sequenced. The homology and phylogenetic analyses were done between the 7 isolates and other CVA16 strains downloaded from Genbank, based on the sequence of VP1 gene. RESULTS: 7 CVA16 strains were isolated from the patients of HFMD in Shanghai, which belonged to different lineages of genotype B. Among them, except for SH-18-CHN02 strain in lineage 1, other CVA16 strains were all in lineage 2. The homology of nucleotide and amino acid of 7 CVA16 strains were 88.8%-99.7% and 99.3%-100% respectively. CONCLUSIONS: 7 CVA16 strains in this study were all genotype B. There were some variations compared with the other CVA16 strains isolated in China before. It suggested that CVA16 strains might have spread for a long time in China, which belonged to several different transmissions. To reveal the genotype and genetic characteristic of CVA16 prevalent in China, the surveillance of CVA16 should be strengthened to get more molecular epidemiologic data.

[Detection of enterovirus 71 and coxsackievirus A16 from children with hand, foot and mouth disease in Shanghai, 2002].

OBJECTIVE: It was noticed that coxsackievirus A16 (CA16) and enterovirus 71 (EV71) were two major etiological agents of hand, foot and mouth disease (HFMD) in children. Recently there were several large outbreaks of HFMD in the Asia-Pacific region, and there was a propensity to cause severe complications or death in children under 5 years of age. The severe forms were associated with EV71 infection. Although epidemics of HFMD have been reported in the mainland of China, few reports about EV71 as the pathogen of HFMD epidemics are available. The present study was conducted to investigate the causal agent of an HFMD epidemic in children in Shanghai from April to June of 2002. METHODS: Totally 102 specimens (including vesicle fluid, stool and throat swabs) were collected from 72 patients with HFMD. The specimens were inoculated into Vero and/or RD cells. At first all the isolates were respectively neutralized by the RIVM pools of enterovirus antiserum, the type-specific antisera to EV71 or to CA16. Secondly all untyped isolates were tested by RT-PCR assay with two specific primer pairs for VP1 genes of EV71 and CA16 respectively. The EV71 and CA16 were identified depending on the size of PCR products. Sequence analyses of VP1 genes of 9 virus strains were performed by the laboratory of China CDC. RESULTS: Viruses were isolated from 91 specimens from 67 patients. Serotyping by neutralization failed for all the isolates. But the RT-PCR results indicated that the viruses isolated from 78 specimens from 58 patients were identified as positive for CA16 and the isolates from 13 specimens from 9 patients were identified as positive for EV71, the ratio between CA16 and EV71 was 6.4:1. The results of sequence analyses were consistent with those of PCR assay. Two EV71 strains isolated in this study belonged to a new lineage (C4) within genogroup C. One patient with EV71-associated HFMD had a complication of encephalitis with convulsion, shock, coma and dyspnea. CONCLUSION: CA16 and EV71 were the primary causes of HFMD during the epidemic. It was the first report of EV71-associated severe encephalitis occurred in patients with HFMD in Shanghai.