Local spread of influenza A (H1N1) viruses without a mutation for the maximum duration of an epidemic season in Japan.

Close observation of the local transmission of influenza A(H1N1) viruses enabled an estimate of the length of time the virus was transmitted without a mutation. Of 4,448 isolates from 11 consecutive years, 237 isolates could be categorized into 57 strain groups with identical hemagglutinin genes, which were monitored for the entire duration of an epidemic season. In addition, 35 isolates with identical sequences were identified at the study site and in other countries within 147 days.

Growth capability of epidemic influenza viruses in Japan since the 2009 H1N1 pandemic.

The correlation of viral growth capability (n = 156) with the viral load in nasopharyngeal swabs (n = 76) was assessed. Epidemic influenza A/H1N1, A/H3N2, and B viruses showed a wide range of growth capability (10-10 copies/mL) in Madin-Darby canine kidney cells. The growth was correlated with the nasopharyngeal viral load (r = 0.

Frequent Isolations of Influenza A Viruses (H1N1)pdm09 with Identical Hemagglutinin Sequences for More Than Three Months in Japan.

Background: Although it has been suggested that antigenic drift does not occur in a single epidemic season in temperate countries, there is not enough evidence on the circulation period of influenza virus with identical nucleotide sequences. Therefore, strains of influenza virus were isolated sequentially during five consecutive epidemic seasons in Japan and their nucleotide sequences were determined.

Methods: Nasal swabs or aspirated nasal discharges were collected from influenza A virus antigen-positive individuals living in Tottori Prefecture, Japan for five consecutive winters starting in 2009-2010, and subjected to viral isolation, determination of hemagglutinin nucleotide sequence and phylogenic analyses.

Molecular phylogenetic analysis of Orientia tsutsugamushi based on the groES and groEL genes.

DNA sequences encoding the GroES and GroEL proteins of Orientia tsutsugamushi were amplified by the PCR and sequenced. Pairwise alignment of full-length groES and groEL gene sequences indicated high sequence similarity (90.4-100% and 90.

Reduced replication capacity of influenza A(H1N1)pdm09 virus during the 2010-2011 winter season in Tottori, Japan.

A novel swine-origin influenza A(H1N1)pdm09 virus has been circulating in humans since March-April, 2009. The 2009-2010 epidemic involved predominantly a single subtype of A(H1N1)pdm09 (at 96%, 46/48) in the sentinel sites of this study. However, A(H1N1)pdm09 started to circulate together with other type/subtype (49%, 33/68) at the first peak in the next epidemic season in 2010-2011: A(H1N1)pdm09/A(H3N2) (9%, 6/68), A(H1N1)pdm09/B (35%, 24/68), and A(H1N1)pdm09/A(H3N2)/B (4%, 3/68).

High incidence of rickettsiosis correlated to prevalence of Rickettsia japonica among Haemaphysalis longicornis tick.

Endemic spotted fever group rickettsiosis was reported in Shimane Prefecture, Japan. From an analysis of 14 clinical cases found in the endemic area, the infectious agent of spotted fever group rickettsiosis was identified as Rickettsia japonica. In this study, we also found that Rickettsia japonica was highly infected with the vector tick, Haemaphysalis longicornis, in the endemic area.

Molecular survey of Babesia microti, Ehrlichia species and Candidatus neoehrlichia mikurensis in wild rodents from Shimane Prefecture, Japan.

A significant number of patients are diagnosed with "fevers of unknown origin" (FUO) in Shimane Prefecture in Japan where tick-borne diseases are endemic. We conducted molecular surveys for Babesia microti, Ehrlichia species, and Candidatus Neoehrlichia mikurensis in 62 FUO cases and 62 wild rodents from Shimane Prefecture, Japan. PCR using primers specific for the Babesia 18S small-subunit rRNA (rDNA) gene and Anaplasmataceae groESL amplified products from 45% (28/62) and 25.

Novel genetic variants of Anaplasma phagocytophilum, Anaplasma bovis, Anaplasma centrale, and a novel Ehrlichia sp. in wild deer and ticks on two major islands in Japan.

Wild deer are one of the important natural reservoir hosts of several species of Ehrlichia and Anaplasma that cause human ehrlichiosis or anaplasmosis in the United States and Europe. The primary aim of the present study was to determine whether and what species of Ehrlichia and Anaplasma naturally infect deer in Japan. Blood samples obtained from wild deer on two major Japanese islands, Hokkaido and Honshu, were tested for the presence of Ehrlichia and Anaplasma by PCR assays and sequencing of the 16S rRNA genes, major outer membrane protein p44 genes, and groESL.