A molecular epidemiological study on common diarrheal viruses was conducted in a children's hospital in Ho Chi Minh City between December 2005 and November 2006. Fecal samples were collected from 502 pediatric patients with acute gastroenteritis, and were screened for eight types of viral agents. Human astroviruses (HAstVs), which were detected with a prevalence of 13.9%, became the second most frequent viral enteropathogen. Although detected in both dry and rainy seasons, the majority (92.8%) of HAstVs in this study were found in the rainy season. Patients aged between 6 and 23 months were found to be more infected from astrovirus when compared to other age groups. The ratio between boys and girls was 2.3:1. The overall mean severity score of astrovirus positive patients was 11.8 +/- 2.45. The mean severity score of the inpatients was statistically higher than that of the outpatients; however, there was no difference in severity scores between the age groups observed. The clinical manifestations of astrovirus infections among the Vietnamese children were diarrhea, vomiting, fever, coughing, and coryza. All of the detected astroviruses belonged to genotype 1. The phylogenetic tree clearly indicated that HAstVs-1 worldwide could be classified into four different lineages, in which, Vietnamese astroviruses and other recently isolated strains from other countries clustered into the distinct lineage, 1d. These results provide important information on astrovirus infections among Vietnamese children.

A prospective study was conducted to evaluate two immunochromatography (ICG) tests for detection of group A rotavirus and norovirus GII, the commercial Dipstick 'Eiken' Rota kit (SA Scientific, USA) and the NV IC-1 stick (Immuno-Probe, Japan). Polymerase chain reaction (PCR) with specific primer pairs (Beg9 and VP7-1', for group A rotavirus; COG2F and G2SKR, for norovirus GII) was used as the reference method. The results of ICG tests were compared with those of reference method. The sensitivity, specificity and agreement between ICG tests and PCR were 87.8%, 93.3% and 89.4%, respectively, for rotavirus ICG test; and 73.7%, 100% and 95.2%, respectively, for norovirus ICG test. The immunochromatography assay for norovirus used in this study could detect not only common noroviruses, but also a novel norovirus GII.4 variant, which emerged in Ho Chi Minh City in 2006. Immunochromatography tests are easy, rapid and useful assays for detection of rotavirus and norovirus among pediatric patients with acute gastroenteritis in Vietnam.

Nucleotide and amino acid sequences of the VP8* gene of five Vietnamese P[6] rotavirus strains detected from hospitalized patients with acute gastroenteritis were analyzed and compared with other human and porcine P[6] rotaviruses. It is of interest that these strains had greatest identity with two Italian porcine rotavirus strains, 134/04-10 and 134/04-11. To our knowledge, these five Vietnamese rotaviruses are the rare P[6] rotavirus strains belonging to lineage I that cluster into sublineage Ic with porcine rotaviruses, and not into sublineage Ia, as other human P[6] rotaviruses have done so far. Sequence analysis of the VP7 gene of these P[6] rotavirus strains was also performed. The results showed that the Vietnamese G9P[6] strain had high similarity with other human G9 rotaviruses, confirming a humananimal reassortant virus, whereas other three G4P[6] strains had best identity with porcine G4 rotavirus strains, suggesting interspecies transmission of rotavirus between porcine and humans. This result provides the important data on molecular characteristics of Vietnamese rotaviruses, and highlights interspecies transmission events of rotaviruses in Vietnam as well as in Asia.

A molecular epidemiological study on common diarrheal viruses was conducted in a children's hospital in Ho Chi Minh City between December 2005 and November 2006. Fecal samples were collected from 502 pediatric patients with acute gastroenteritis, and were screened for the presence of norovirus (NoV) and sapovirus (SaV). NoVs GII and SaVs were detected in 6.4% and 1.2% specimens, respectively, while there was no NoV GI found among studied samples. NoVs could be identified through the year, except in April and July, with the peak of detection rate (62.5%) during the rainy season. Conversely, four out of six (66.7%) of the SaV strains were identified during the dry season. Patients aged between 6 and 23 months were found to be more infected by NoVs. The overall mean severity score of norovirus-positive patients was 9.8 +/- 3.6, and no significant difference of severity scores among patients belonged to different age groups, gender and place of living. The results of phylogenetic analysis showed the diversity of caliciviruses circulating in the area, and various types of recombination were identified among NoVs and SaVs detected. These results provide important information on calicivirus infections among Vietnamese children.

Twenty-eight strains of P(8), four of P(4) and one of P(19) rotavirus, isolated in Ho Chi Minh City, Vietnam, during 2002-2003, were investigated by sequence analysis of the VP4 gene. Seven of the 28 P(8) rotavirus VP4 sequences clustered in the P(8)-3 lineage, or the rare, so-called OP354-like lineage. Amino-acid sequence comparison revealed that Vietnamese P(8)-3 rotaviruses were generally very similar to Malawian strains, including the prototype OP354 strain. The numerical severity scores of diarrhoeal disease caused by the Vietnamese P(8)-3 rotaviruses were statistically higher than those of diarrhoeal disease caused by rotaviruses in the more common P(8)-2 lineage. Sequence and phylogenetic analysis of the VP4 gene of a Vietnamese G9P(19) rotavirus isolate showed a high degree of homology with the cognate genes of other human and porcine rotaviruses, including the prototype 4F strain.