Molecular characterization of rotavirus diarrhea among children in South Korea: detection of an unusual G11 strain

Changing distribution of age, clinical severity, and genotypes of rotavirus gastroenteritis in hospitalized children after the introduction of vaccination: a single center study in Seoul between 2011 and 2014

Background

This study aimed to explore changes in clinical epidemiology and genotype distribution and their association among hospitalized children with rotavirus gastroenteritis after the introduction of vaccines.

Methods

Between November 2010 and October 2014, hospitalized children with acute gastroenteritis were enrolled. Rotavirus genotypes were confirmed through reverse transcription-polymerase chain reaction (RT-PCR), semi-nested PCR, and sequencing. Clinical information including vaccination status and the modified Vesikari scores were collected.

Results

Among 179 children with rotavirus infection, nineteen (10.6 %) were completely vaccinated. During the study period, the number of children between three and 23 months of age decreased significantly compared to the number of children older than 24 months of age (P = 0.010), who showed lower diarrhea severity (duration, P = 0.042; frequency, P = 0.021) but higher vomiting severity (P = 0.007, 0.036) compared to the former. Vaccination status was also significantly associated with lower vomiting severity after adjustment for age (frequency only, P = 0.018). The predominant genotypes were G2P[4] (18.4 %), G1P[8] (14.5 %), and G1P[4]P[8] (12.8 %), and the prevalence of genotypes with uncommon and mixed combinations was more than 50 %. Children infected with G2P[4] strains tended to be older (P = 0.005) and had more severe vomiting (P = 0.018, 0.006) than those with G1P[8].

Conclusions

Increase in age of infected, hospitalized children was accompanied by change in clinical severity during 2011–2014 after the introduction of vaccines in Seoul. Clinical severity was also associated with vaccination status and genotype. Long-term large scale studies are needed to document the significance of the increase in genotypes of uncommon and mixed combinations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-1623-y) contains supplementary material, which is available to authorized users.

Analysis of rotavirus genotypes in Korea during 2013: an increase in the G2P[4] genotype after the introduction of rotavirus vaccines

BACKGROUND

Group A rotavirus is the leading cause of acute gastroenteritis in children worldwide. We investigated G and P genotypes of group A rotavirus strains isolated from patients during 2013 and investigated which genotypes were identified from vaccinated patients.

METHODS

From January to December 2013, 2235 fecal specimens were tested for rotavirus antigen, of which 374 specimens (16.7%) showed positive results. Strains from 288 rotavirus-positive specimens were genotyped using PCR and sequencing, and individual patients' corresponding vaccine histories were investigated through the Korean Center for Disease Control website.

RESULTS

G2 (22.6%) and P[4] (24.0%) were the most frequently identified G and P genotypes, respectively; accordingly, G2P[4] (19.8%) was the most prevalent G/P genotype observed in this period. G4P[6] (10.1%) was the second most prevalent G/P genotype and was mostly detected in neonates. Other genotypes, G1P[8], G9P[8], G1P[6], and G3P[6], were also detected. Of 288 rotavirus-positive specimens, 48 specimens were obtained from previously vaccinated patients. G2P[4] was also the genotype most frequently isolated from vaccinated patients. VP7 epitope analysis of G1P[8] and G2P[4] strains showed at least one amino acid differences in comparison with Rotarix and RotaTeq vaccine strains. The genotypic distribution of rotavirus strains in Korea has been shown temporal and geographical differences.

CONCLUSION

This study showed that G2P[4] was the genotype most frequently isolated from both vaccinated and unvaccinated patients in Korea during 2013. However, it is unclear whether the change of predominant genotype is due to the effect of vaccination or due to natural variation.

Review of global rotavirus strain prevalence data from six years post vaccine licensure surveillance: is there evidence of strain selection from vaccine pressure?

Comprehensive reviews of pre licensure rotavirus strain prevalence data indicated the global importance of six rotavirus genotypes, G1P[8], G2P[4], G3P[8], G4P[8], G9P[8] and G12P[8]. Since 2006, two vaccines, the monovalent Rotarix (RV1) and the pentavalent RotaTeq (RV5) have been available in over 100 countries worldwide. Of these, 60 countries have already introduced either RV1 or RV5 in their national immunization programs. Post licensure vaccine effectiveness is closely monitored worldwide. This review aimed at describing the global changes in rotavirus strain prevalence over time. The genotype distribution of the nearly 47,000 strains that were characterized during 2007-2012 showed similar picture to that seen in the preceding period. An intriguing finding was the transient predominance of heterotypic strains, mainly in countries using RV1. Unusual and novel antigen combinations continue to emerge, including some causing local outbreaks, even in vaccinated populations. In addition, vaccine strains have been found in both vaccinated infants and their contacts and there is evidence for genetic interaction between vaccine and wild-type strains. In conclusion, the post-vaccine introduction strain prevalence data do not show any consistent pattern indicative of selection pressure resulting from vaccine use, although the increased detection rate of heterotypic G2P[4] strains in some countries following RV1 vaccination is unusual and this issue requires further monitoring.

Rotaviruses: is their surveillance needed?

Rotaviruses, a major cause of gastroenteritis in children worldwide accounts for around 0.5 million deaths annually. Owing to their segmented genome and frequently evolving capability, these display a wide variation in their genotypes. In addition to commonly circulating genotypes (G1, G2, G3, G4, G9, P[4] and P[8]), a number of infrequent genotypes are being continuously reported to infect humans. These viral strains exhibit variation from one geographical setting to another in their distribution. Though the introduction of vaccines (RotaTeq and Rotarix) proved to be very effective in declining rotavirus associated morbidity and mortality, the number of infections remained same. Unusual genotypes significantly contribute to the rotavirus associated diarrhoeal burden, may reduce the efficacy of the vaccines in use and hence vaccinated individuals may not be benefited. Vaccine introduction may bring about a notable impact on the distribution and prevalence of these viruses due to selection pressure. Moreover, there is a sudden emergence of G2 and G3 in Brazil and United States, respectively, during the years 2006-2008 post-vaccination introduction; G9 and G12 became predominant during the years 1986 through 1998 before the vaccine introduction and now are commonly prevalent strains; and disparity in the predominance of strains after introduction of vaccines and their natural fluctuations poses a vital question on the impact of vaccines on rotavirus strain circulation. This interplay between vaccines and rotavirus strains is yet to be explored, but it certainly enforces the need to continuously monitor these changes in strains prevalence in a particular region. Furthermore, these fluctuations should be considered while administration or development of a vaccine, if rotavirus associated mortality is ever to be controlled.

Prevalence of rotavirus genotypes in South Korea in 1989-2009: implications for a nationwide rotavirus vaccine program

The epidemiology of human group A rotavirus was analyzed by examining genotypic data acquired from 1989 to 2009 in South Korea. This information was derived from all the available published articles on rotavirus studies in South Korea, retrieved from both the PubMed and KoreaMed databases. Four common G types (G1, G2, G3, and G4) and three common P types (P[8], P[4], and P[6]) accounted for approximately 93% and 99% of the rotavirus reports, respectively. The G9 type was frequently detected after 2000, and because of this prevalence, it is considered to be the fifth most important G type rotavirus after the G1.G4 genotypes. Less common G types of the virus such as G12, G11, and G10 were detected in some geographic settings, and it is important to consider the context of these subtypes and their epidemiological significance. The P[9] virus genotype was observed in the study and has been discussed in many other studies; however, the P[3], P[10] and P[25] genotypes were rarely detected in the epidemiological research. In general, the distributions of the G and P genotypes showed temporal and geographical fluctuations, and a nationwide rotavirus vaccine program that targeted these genotypes demonstrated effectiveness in protecting against the circulating rotavirus strains. However, further analysis is needed to determine the true long-term effectiveness of these vaccines; the analysis should also consider the unexpected effects of vaccinations, such as vaccine-induced diseases, herd immunity, and changes in host susceptibilities.

Molecular characterization of group A bovine rotavirus in southeastern and central-western Brazil, 2009-2010

Rotavirus is an important cause of neonatal diarrhea in humans and several animal species, including calves. A study was conducted to examine 792 fecal samples collected from calves among 65 dairy and beef herds distributed in two of Brazil's major livestock producing regions, aiming to detect the occurrence of rotavirus and perform a molecular characterization of the rotavirus according to G and P genotypes in these regions. A total of 40 (5.05%) samples tested positive for rotavirus by the polyacrylamide gel electrophoresis (PAGE) technique. The molecular characterization was performed by multiplex semi-nested RT-PCR reactions, which indicated that the associations of genotypes circulating in herds in Brazil's southeastern region were G6P[11], G10P[11], G[-]P[5] + [11], G[-]P[6] in the state of São Paulo and G6P[11], G8P[5], G11P[11], G10P[11] in the state of Minas Gerais. In the central-western region, the genotypes G6P[5] + [11], G6P[5], G8P[-], G6P[11], G [-] P[1], G[-] P[11], and G[-] P[5] were detected in the state of Goiás, while the genotypes G6P[5], G8[P11], G6[P11], G8[P1], G8[P5], G6[P1] were circulating in herds in the state of Mato Grosso do Sul. The genotypic diversity of bovine rotavirus found in each region under study underlines the importance of characterizing the circulating samples in order to devise the most effective prophylactic measures.