The problem of predicting the culprit of a future flu pandemic in connection with the emerging cow epizootic caused by the avian H5N1 influenza strain is analyzed. The resulting epizootic in cows is considered as the acquisition of a new host by the H5N1 virus. The reproductive cycle of the H5N1 virus is adapted to high temperatures; in cows, body temperature varies and is closer to bird body temperature than to human body temperature. The nucleoprotein of the H5N1 virus is characterized by a high content of arginine and lysine, which determines the optimum replication and transcription of the virus at elevated body temperature of the host. In this aspect, acquiring the H5N1 virus as a cow host, rather than a human, is more optimal. Another feature of the H5N1 virus, which excludes the possibility of its transmission into the human population, is related to the characteristics of its internal proteins, in particular, the biomarker of pandemic influenza viruses. The invariance matrices of all primary structures of the internal proteins of the H5N1 virus differ significantly from those of the strains of the 1918, 1957, 1968, and 2009 influenza pandemics, which also does not support the prediction of the H5N1 virus as a harbinger of a future flu pandemic.

CONCLUSION

Based on the history of the last four influenza pandemics and a comparison of the biological properties and molecular characteristics of hemagglutinins of influenza viruses of the H1N1 and H3N2 subtypes, the H1N1 subtype virus is assumed to be the most likely causative agent of a future influenza pandemic.