RESUMO
Objective To understand epidemic characteristics of human influenza A and the genetic and antigenic variations of H1N1 influenza A isolates in Shanghai area in 2009. Methods Throat swabs were collected from patients with influenza-like illness in the sentinel surveillance clinic in Shanghai area in 2009, then inoculated in Madin-Darby canine kidney (MDCK) cell lines. The types of influenza were identified by direct immunofluorescence assay (DIF) and the subtypes were determined by reverse transcriptase-polymerase chain reaction (RT-PCR). Segments of hemagglutinin (HA) and neuraminidase (NA) genes of some 2009 H1N1 influenza A isolates were amplified and sequenced. HA and NA gene mutations of 2009 H1N1 influenza A isolates were analyzed. Results Seasonal H1N1 and H3N2 influenza A viruses co-circulated during the spring of 2009 in Shanghai area. Seasonal H3N2 began to co-circulate with 2009 H1N1 in August (the 32nd week) and finally2009 H1N1 became dominate since the 40th week. The phylogenetic tree of 2009 H1N1 HA segment revealed that the isolates from different regions and months were interspersed with each other, but all were clustered into one branch which closed to strains in Spain, Russia, Denmark and other European countries. Mutations were found in some HA amino acid sites, but none of them was in the antigenic determinant region. No change was observed in the 274 NA amino acid residues which were related to the drug resistance to oseltamivir. PB2 protein analysis showed that the 627 and 701 amino acid residues were glutamic acid and aspartic acid respectively, which were the same encoded amino acid with avian flu PB2 protein. Conclusions Seasonal H1N1 and H3N2 co-circulated in the spring of 2009, then both 2009 H1N1 and seasonal H3N2 were prevalent in Summer and Autumn, and 2009 H1N1 finally became dominate in Autumn. Compared to early 2009 H1N1 strains, variations are detected in H1N1 influenza A viruses, but none of them has epidemiological influence, and viruses still show high affinity with human and low-pathogenic characteristics.
RESUMO
Objective To determine the persistence time of genotype 4 hepatitis E (HE) viremia after the onset of clinical symptoms in HE patients and provide essential data for study on HE epidemiologieal transmission, so that to evaluate potential contagiousness of HE patients after clinical stage. Methods The first serum samples from 162 HE patients after hospitalized in Eastern China were collected and tested for hepatitis E virus (HEV) RNA by nested reversed transcription- polymerase chain reaction (RT-PCR). The persistence time of HEV viremia after the onset of clinical symptoms was estimated with Kaplan-Meier survival analysis. Results HEV RNA was detectable in 101 out of 162 serum samples with positive rate of 62.35%, which was all grouped to genotype 4 by homology analysis. Furthermore, HEV RNA was detectable in 74 (64.91%) out of 114 male and 27 (56.25%) out of 48 female, which was not significantly different (χ2 = 1.08, P=0. 30). Kaplan-Meier survival analysis showed that the median persistence time of HEV genotype 4 viremia was 24 days after the onset of clinical symptoms (95% CI: 18-30 days), which meant that the viremia of 50% HE patients remaining detectable up to 24 days after the onset. The 75% and 25% percentiles were 14 days and 31 days, respectively. There was no significant difference of viremia persistence time between male and female (Breslow test: P=0.98, Tarone-Ware test: P=0.91). Conclusions The viremia of 75% patients with HEV genotype 4 infection could persistent until 2 weeks after the onset of clinical symptoms and that of some patients could persistent over 1 month. It is indicated that the viremia is still persistent and HE patient could be a reservoir even after the clinical symptoms disappeared and biochemical marks normalized.