influenza monitor

Thus far, H1N1 has exhibited moderate pathogenicity while proving efficient at transmission and replication. H5N1 by contrast is highly pathogenic, but has not evidenced capacity for sustained human-to-human transmission. This has been the human experience. It stands to reason, we would expect to see similar results when H1N1 is tested (in vivo) in other mammals.

• US Govt researchers compared the pathogenenicity of pandemic H1N1 in mice with several other viruses to include a reconstructed 1918 virus, a 1976 H1N1 virus, a highly pathogenic H5N1 (avian flu) virus, and a triple reassortment human virus that has been circulating in pigs for at least a decade prior to pH1N1. They found that all “2009 H1N1 viruses replicated efficiently in the lungs of mice and possessed a high degree of infectivity, but did not cause lethal disease or exhibit extrapulmonary virus spread.” 2009 H1N1 “viruses isolated from fatal cases did not demonstrate enhanced virulence in this model compared with isolates from mild human cases.”
• A similar experiment by Dutch researchers compared that pathogenicty of pH1N1 in ferrets with seasonal H1N1 and highly pathogenic H5N1. The results “showed that the new (i.e. pandemic) H1N1 virus causes pneumonia in ferrets intermediate in severity between that caused by seasonal H1N1 virus and by HPAI H5N1 virus. The new (pandemic) H1N1 virus replicated well throughout the lower respiratory tract and more extensively than did both seasonal H1N1 virus (which replicated mainly in the bronchi) and HPAI H5N1 virus (which replicated mainly in the alveoli).”
• Both studies are consistent with earlier research from a team led by Dr Yoshihiro Kawaoka at the University of Wisonsin, Madison, which compared the effects of H1N1 and seasonal in mice, ferrets and monkeys. Their results indicated that the “H1N1 virus (replicated) much more efficiently in the respiratory system than seasonal flu and (caused) severe lesions in the lungs similar to those caused by other more virulent types of pandemic flu.”
• Recent research also led by Dr. Kawaoka engineered 254 combinations of reassorted viruses between a low-pathogenic avian H5N1 and a human seasonal H3N2 strains and subsequently tested a subset of these in mice. Some 96 viruses in this mix were found to be highly replicable. The team tested 75 H5N1 and H3N2 hybrids in mice. Of this group “forty-five viruses were less pathogenic than the avian H5N1 parent, 8 were as pathogenic, and 22 were more pathogenic.” The findings suggested that “human PB2 (gene) is required for the emergence of substantially virulent hybrids.”

No mice, ferrets or monkeys were harmed in the making of this post.

CIDRAP: Study yields highly pathogenic avian, human flu virus mix
J Inf Disease: Severity of Pneumonia Due to New H1N1 Influenza Virus in Ferrets Is Intermediate between That Due to Seasonal H1N1 Virus and Highly Pathogenic Avian Influenza H5N1 Virus
J Virol: Pathogenesis of Pandemic Influenza A (H1N1) and Triple-Reassortant Swine Influenza A (H1) Viruses in Mice.
PNAS: Reassortment between avian H5N1 and human H3N2 influenza viruses creates hybrid viruses with substantial virulence
UW Madison: A new, highly detailed study of the H1N1 flu virus shows that the pathogen is more virulent than previously thought

Tagged: avian influenza, flu, h1n1, h5n1, influenza, International News, pandemic flu, swine flu, US News