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Surveillance of bat betacoronaviruses is crucial for understanding their spillover potential. We isolated bat sarbecoviruses from Rhinolophus cornutus bats in multiple locations in Japan. These viruses grew efficiently in cells expressing R. cornutus angiotensin converting enzyme-2, but not in cells expressing human angiotensin converting enzyme-2, suggesting a narrow host range. [ABSTRACT FROM AUTHOR]

Highly pathogenic H5N1 influenza viruses continue to cause concern, even though currently circulating strains are not efficiently transmitted among humans. For efficient transmission, amino acid changes in viral proteins may be required. Here, we examined the amino acids at positions 627 and 701 of the PB2 protein. A direct analysis of the viral RNAs of H5N1 viruses in patients revealed that these amino acids contribute to efficient virus propagation in the human upper respiratory tract. Viruses grown in culture or eggs did not always reflect those in patients. These results emphasize the importance of the direct analysis of original specimens. [ABSTRACT FROM AUTHOR]

Although two classes of antiviral drugs, M2 ion channel blockers and neuraminidase (NA) inhibitors, are available to combat seasonal H1N1 and H3N2, and highly pathogenic avian (e.g., H5N1) influenza, the emergence and spread of drug-resistant viruses is of great concern. Animal studies suggest that combination chemotherapy with M2 and NA inhibitors may be an effective option to reduce the emergence of drug-resistant viruses. In this study, we evaluated the antiviral susceptibility of clinical isolates from immunocompetent children infected with a seasonal influenza A virus and treated with a combination of amantadine and oseltamivir. We found that amantadine-resistant viruses emerged during this combination treatment. While viruses with mutations known to confer oseltamivir resistance were not detected, we found viruses with mutations in NA that reduced sialidase activity and viruses with hemagglutinin mutations. These findings suggest that while the amantadine-oseltamivir combination is an effective therapeutic option for influenza, drug-resistant viruses do appear with this combination therapy. [ABSTRACT FROM AUTHOR]

Highly pathogenic avian influenza H5N1 viruses are circulating in many countries. We recently discovered that these viruses have been transmitted to pigs on multiple occasions in Indonesia. To investigate whether avian H5N1 influenza viruses adapted to mammals through their introduction into pigs, we examined the growth of avian and swine isolates in cell culture and compared their pathogenicity in mice. We found that swine isolates were less virulent to mice than avian isolates, suggesting that the viruses became attenuated during their replication in pigs. Continuous surveillance of H5N1 viruses among pigs is clearly warranted. [ABSTRACT FROM AUTHOR]