Influenza Virus (H5N1) in Live Bird Markets and Food Markets, Thailand

A surveillance program for influenza A viruses (H5N1) was conducted in live bird and food markets in central Thailand during July 2006–August 2007. Twelve subtype H5N1 viruses were isolated. The subtype H5N1 viruses circulating in the markets were genetically related to those that circulated in Thailand during 2004–2005

Probable Tiger-to-Tiger Transmission of Avian Influenza H5N1

During the second outbreak of avian influenza H5N1 in Thailand, probable horizontal transmission among tigers was demonstrated in the tiger zoo. Sequencing and phylogenetic analysis of those viruses showed no differences from the first isolate obtained in January 2004. This finding has implications for influenza virus epidemiology and pathogenicity in mammals

Avian Influenza H5N1 in Tigers and Leopards

Influenza virus is not known to affect wild felids. We demonstrate that avian influenza A (H5N1) virus caused severe pneumonia in tigers and leopards that fed on infected poultry carcasses. This finding extends the host range of influenza virus and has implications for influenza virus epidemiology and wildlife conservation

Genetic characterization of 2008 reassortant influenza A virus (H5N1), Thailand

In January and November 2008, outbreaks of avian influenza have been reported in 4 provinces of Thailand. Eight Influenza A H5N1 viruses were recovered from these 2008 AI outbreaks and comprehensively characterized and analyzed for nucleotide identity, genetic relatedness, virulence determinants, and possible sites of reassortment. The results show that the 2008 H5N1 viruses displayed genetic drift characteristics (less than 3% genetic differences), as commonly found in influenza A viruses. Based on phylogenetic analysis, clade 1 viruses in Thailand were divided into 3 distinct branches (subclades 1, 1.1 and 1.2). Six out of 8 H5N1 isolates have been identified as reassorted H5N1 viruses, while other isolates belong to an original H5N1 clade. These viruses have undergone inter-lineage reassortment between subclades 1.1 and 1.2 and thus represent new reassorted 2008 H5N1 viruses. The reassorted viruses have acquired gene segments from H5N1, subclade 1.1 (PA, HA, NP and M) and subclade 1.2 (PB2, PB1, NA and NS) in Thailand. Bootscan analysis of concatenated whole genome sequences of the 2008 H5N1 viruses supported the reassortment sites between subclade 1.1 and 1.2 viruses. Based on estimating of the time of the most recent common ancestors of the 2008 H5N1 viruses, the potential point of genetic reassortment of the viruses could be traced back to 2006. Genetic analysis of the 2008 H5N1 viruses has shown that most virulence determinants in all 8 genes of the viruses have remained unchanged. In summary, two predominant H5N1 lineages were circulating in 2008. The original CUK2-like lineage mainly circulated in central Thailand and the reassorted lineage (subclades 1.1 and 1.2) predominantly circulated in lower-north Thailand. To prevent new reassortment, emphasis should be put on prevention of H5N1 viruses circulating in high risk areas. In addition, surveillance and whole genome sequencing of H5N1 viruses should be routinely performed for monitoring the genetic drift of the virus and new reassorted strains, especially in light of potential reassortment between avian and mammalian H5N1 viruses

The virus kinetic study from the supernatants of H5N1-infected hNPCs at different time points post infection.

<p>The hNPCs supported H5N1 virus infection as determined by a statistical significant increase of virus titers from 10² TCID₅₀/mL at 6 hpi, which reached a maximum titer of 10⁷ TCID₅₀/mL at 48 hpi. It subsequently declined to about 10⁴ TCID₅₀/mL at 72 hpi. Results were obtained from three separate experiments. Data represented are the mean ± standard error. Asterisks indicated statistically significant differences (<i>p</i>-value<0.05). Dotted line represents detection limit of the assay.</p

The cytopathic effects (CPEs), electron micrographs, and average cell number of hNPCs following H5N1 virus infection.

<p>At 24 hpi, 48 hpi, and 72 hpi, H5N1-infected hNPCs revealed the pronounced CPEs, such as cell rounding up, vacuolation, short processes of the cells, and cell detachment, while no CPEs were observed in the mock-infected control cells (<b>A</b>). Transmission electron micrographs (<b>B)</b> showed the changes in hNPC induced by H5N1 virus by shrinkage and condensation of the nucleus and chromatin, disruption of the cytoplasmic membrane and increased in cellular vacuolation (N = nucleus; V = vacuolation; M: mitochondria). The detachment of H5N1-infected hNPCs was observed by the significant decreased of average cell number per field at 24–72 hpi compared to the UV-inactivated H5N1- and mock-infected controls (<b>C</b>). Scale bar in A ≈100 μm, scale bar in B ≈ 1μm.</p