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Historically speaking, the records reveal the earliest known influenza pandemic was in 1580. Apparently, it started in Asia and consequently spread almost to every other continent. After a gap of more than 100 years in Russia during 1729, a rapidly moving influenza virus went to reach all over the globe within a span of 3 years, creating another menacing outbreak. Similarly, another one broke out in China during 1830-1833. Throughout history, the most debilitating and talked pandemic was the Spanish Flu, starting in Russia in 1889. It affected almost one-third of the total world population with a mortality of around 50 million people. This became the first known case of worldwide H1N1 outbreak. Two more flu pandemics were equally menacing if we consider the later years, i.e., 1957 Asian Flu (H2N2) and 1968 Hong Kong flu (H3N2). Interestingly in 2009, a new H1N1 strain caused an outbreak but the severity was mild owing to the already developed immunity against the previous similar strain.
Influenza is an infectious disease, recurs frequently in various regions of the world and spreads quickly. Main influenza types include A, B, C, and D; out of them, type A is the most common and notorious for causing global pandemics. Nomenclature of the A-type is based on two surface proteins- Hemagglutinin (H) and Neuraminidase (N), the former having 18 subtypes and the latter with 11 subtypes, making it possible to form a large number of combinations. This possibility is the reason for constant genetic variations leading to severe outbreaks.
The latest case of avian influenza H5N8 outbreak is a testament to the unending global threat still prevalent despite advancements in research. Another strain known for avian flu is the H5N1. Clearly, the host for these avian strains is wild aquatic birds. Considering epidemiological studies, a pattern has been observed in terms of the spread of influenza and the recurring frequency. It might be predictable as to when the next outbreak will take place. Vaccine development is already in progress but the main problem behind limited success is the emergence of new strains frequently.
Taking all that into consideration, WHO has launched a global web-based tool called FluNet in 1997 which is responsible for influenza virus surveillance with a focus on each country with the weekly updating of data. Mathematical models based upon the likely variations possible in influenza and their transmission dynamics might be useful in the long run. These representations must take into account the seasonal flu situation, primarily prevalent at least twice a year. Overall, the upcoming years necessitate researchers to find possible mechanisms to tackle this influenza occurrence.