GlobalHealth Threats

A recent journal article, published in Lancet Infectious Diseases, describes how avian influenza H5N1 dominated the influenza infections in animals before the year 2013. At least 700 cases were detected worldwide but H7N9 soon took over and emerged as the new virus. It has now surpassed H5N1 in numbers. There is still no evidence of human-to-human infection of both H5N1 and H7N9.
Human cases of H7N9 infections settled into a seasonal pattern and there was a gradual decrease in numbers during the first to the fourth epidemic. However, in 2016-2017 during the fifth epidemic, the virus transited to a highly pathogenic form for poultry and there was an increase in cases among humans. This happened because the epidemic started earlier in the year and affected a larger proportion of middle-aged people and in several countries. Additionally several provinces which reported infections recorded a shift from urban to semi-urban and rural regions. However, it was reassuring that there were no major shifts in other clinical aspects of the infections.
The understanding of the true prevalence of the virus in the various avian sectors in China is still not clear. The authors concluded “The initial evidence suggests that human disease with low pathogenic and highly pathogenic forms of A H7N9 are not markedly different, but the full effect is yet to be established."