Seroprevalence of noroviruses in swine.

Noroviruses (NVs) are important human pathogens that cause acute gastroenteritis. Genetically related animal enteric NVs have also been described, but there is no evidence of interspecies transmission of NVs. In this study we characterized antibody prevalence among domestic pigs by using recombinant capsid antigens of two human NVs (Norwalk and Hawaii) and one swine NV (SW918) that is genetically related to GII human NVs. Recombinant SW918 capsid protein expressed in baculovirus self-assembled into virus-like particles (VLPs) that were detected by antibodies against GII (Hawaii and Mexico), but not GI (Norwalk and VA115), human NVs. NVs recognize human histo-blood group antigens as receptors, but SW918 VLPs did not bind to human saliva samples with major histo-blood group types. Seventy-eight of 110 (71%) pig serum samples from the United States and 95 of 266 (36%) pig serum samples from Japan possessed antibodies against SW918. Serum samples from pigs in the United States were also tested for antibodies against human NVs; 63% were positive for Norwalk virus (GI) and 52% for Hawaii virus (GII). These results indicate that NV infections are common among domestic pigs; the finding of antigenic relationships between SW918 and human NVs and the detection of antibodies against both GI and GII human NVs in domestic animals highlights the importance of further studies on NV gastroenteritis as a possible zoonotic disease.

Seroepidemiological analysis of influenza pandemics in Shizuoka Prefecture and all Japan.

(1) Seroepidemiological analysis of influenza pandemics (1986-2003) in Shizuoka Prefecture and all Japan revealed differences in geographical, annual, seasonal, and age distributions. (2) For 17 years, the pandemics generally began at the 50th week every year showing over 1.0 patient/clinic, reached the peak at 5th week the following year, and ended over 10-15th week. Two big A/H3N2 pandemics were seen in 1989/1990 and 1997/1998 seasons, claiming over 1 million patients in Japan. (3) As herald strains, A/H3N2 strains (A/Sydney-like) were found in October 1999, and B strains (B/Victoria- and B/Yamagata-like) were detected in July and November 1998 and, in August and December 2000 in Shizuoka. B/Shizuoka/1/98 strain was registered internationally as a vaccine-recommended strain. (4) A/H3N2 and B viruses were detected in 55-78% of flu patients (almost under 10 years) with encephalopathy in 1999/2000 and 78-91% in 2000/2001 by MDCK and reverse transcription polymerase chain reaction (RT-PCR) methods. (5) High hemagglutination inhibition (HI) titers over 40 in 250 persons were shown against A/Sydney/5/97 (H3N2), A/Yokohama/8/98 (H3N2), A/Panama/2007/99 (H3N2) and A/Moscow/10/99 (H1N1) strains, while low titers showed against A/Beijing/262/95 (H1N1) and A/New Caledonia/20/99 (H1N1), and B/Beijing/243/97, B/Shangdong/7/97 and B/Yamanashi/106/98 strains in 1998-2000. (6) In anti-HA titers against A/H3N2, A/H1N1 and B subtypes, clear generation gaps were observed between children (0-19 years), adults (20-59 years) and old men (over 60 years). (7) The pandemics are dependent on host immunity (acquired and vaccinated) and climatic conditions (low temperature, low humidity and limited rainfall), considering highly pathogenic avian influenza (HPAI) viruses (A/H5N1, A/H7N7) like severe acute respiratory syndrome (SARS) corona virus in 2002-2003.

Viruses detected in the caecum contents of healthy pigs representing a new genetic cluster in genogroup II of the genus "Norwalk-like viruses".

Viruses of the genus 'Norwalk-like viruses' (NLVs) detected in humans have been genetically classified into two major genetic groups, genogroups I and II (GI and GII), which together are made up of at least 14 genetic subgroups. However, a comparable classification of NLVs in other species remains to be carried out. We sequenced a 2-kb region from within the RNA polymerase gene to the 3' end of open reading frame 2 (ORF2) of two NLV strains previously detected in the caecum contents of healthy pigs. The sequences of the entire ORF2 of these two NLV strains were analyzed for their genetic relationships to 15 human strains, which have already been reported and used as references for the genetic classification of human NLV strains, and additional two strains; one, a human strain which has recently been reported and appears to represent a new genetic subgroup of GII; and the other, an animal NLV strain. Analysis of a matrix showing pairwise identities and topology of a neighbor-joining tree showed that the two swine strains could be classified into a new genetic subgroup of GII on the basis of the amino acid sequences of the entire capsid protein. Grouping of the two swine strains was well corroborated by results of similar analyses of nucleotide sequences of the entire ORF2 and of a 510 base region at the 3' end of ORF1.