Abstract
Influenza virus and its various strains are a significant risk for the global health; influenza and its various strains have caused various periodic outbreaks and pandemics. As we delve into this review, it studies the history and the threat possessed by the four prominent strains of influenza H1N1, H3N2, H7N9, and H9N2. It also examines some of recent and notable outbreaks posed by these influenza strains. In 2009, the H1N1 pandemic was originated in the swine and was spread worldwide rapidly. This outbreak highlighted the gaps in the preparations and response in global healthcare system. The other strain H3N2 with a long history of frequent outbreaks distresses the public health and the health care sectors due to its evolution and the ability to adapt. In 2013 China, a novel strain was identified with a high mortality rate and the potential for human-to-human transmission remains a concern to the public health. Another strain H9N2 though less infectious is being monitored for its ability to cause pandemics in the future, and its distinct genetic makeup and sporadic human infections are causes for worry. This review outlines their differences and similarities, the importance of vigilant surveillance, effective treatment strategies, and the preparedness measures to mitigate any future influenza outbreaks.