H5 and H9 Avian Influenza – potential re-emergent zoonotic threats to humans

Purpose of review This review aims to discuss the current state of human infections with Avian Influenza A (H5) and (H9) viruses, to support awareness of the global epidemiology among clinicians and public health professionals interested in emerging respiratory infections. Recent findings Among increasing numbers of detections in avian species of Avian Influenza A(H5N1) clade 2.3.4.4b globally, reported human cases of severe infection have been rare. Enhanced surveillance of persons exposed to avian species infected with Influenza A (H5N1) clade 2.3.4.4b in different countries has identified small numbers of asymptomatic individuals with Avian Influenza A (H5N1) detected by PCR from the upper respiratory tract; some of these instances have been considered to represent contamination rather than infection. There have also been recent sporadic human cases of Avian Influenza A(H9N2) internationally, including in China and Cambodia. Summary Human infections with Avian Influenza A(H5) and (H9) viruses remain of interest as an emerging infection both to clinicians and public health professionals. While maintaining effective surveillance is essential, one health strategies to control infection in avian species will be key to mitigating these risks.