 We as humans experience flu all the time. We get it at least once a year. But do birds get flu? Yes they do. Here is everything you need to know about avian flu. See avian influenza is also known as bird flu. It refers to the infection of birds with avian influenza type A viruses. It is very contagious among birds. See these viruses they naturally spread among wild aquatic birds worldwide. Here wild aquatic birds include water birds, waterfowl such as ducks, geese, swans, gulls, terns and shore birds. Apart from this also know that influenza A viruses have been detected and are known to circulate in seven different animal species or groups. And this includes domestic poultry, other bird species, swine, horses, dogs and bats. Now this is about the basics of the avian influenza which is also known as bird flu. Now coming to the types. See there are four types of influenza virus. They include type A, B, C and D. Just look at this table. This table contains the different influenza viruses and their nature. Influenza A it infects a wide range of animals including birds and B it mainly infects humans. Now coming to see it infects humans and pigs but it is more rare than type A and B. Now coming to influenza D it infects cattle. So these are the types. Now depending on the host where it origins influenza A viruses can be classified as avian influenza, swine influenza or other types of animal influenza viruses. For example avian influenza is otherwise called as bird flu and this virus have subtypes such as H5N1, H9N2 and there is also swine influenza which is also called as swine flu and this virus has subtypes such as H1N1 and H3N2. See all of these animal influenza type A viruses are distinct from human influenza viruses and they do not easily transmit among humans but know that still there is a chance of transmission from animals to humans. Now these are all the types of influenza. Firstly we saw the broad classification and after that we saw the classification which depends on the host where it origins. Now apart from these classification there are also subtypes of influenza virus A based on the two proteins that the virus have on their surfaces. See what are those two proteins? One is hemagglutinin which is denoted by capital H and the other one is neuraminidase which is denoted by capital N. See on the whole there are 18 different hemagglutinin subtypes and 11 different neuraminidase subtypes. So what does this mean? The subtypes ranges from H1 through H18 and N1 through N11 respectively. See these are known to occur in a number of different combinations. Among these different subtypes H5 and H7 are known to include highly pathogenic viruses and particularly H5N1 is a cause for the current concern. See H5N1 causes disease in chickens and other species of birds and this is one perception of classification. Now in particular take this avian influenza virus. See it has multiple strains or types. As we all know COVID-19 had multiple strains and variants right. Likewise this avian influenza virus also has multiple strains and these strains can be divided into two and this is done based on its ability to cause disease in poultry. And what are the two divisions? They are highly pathogenic avian influenza and low pathogenic avian influenza. See in this the LPAI which is nothing but the low pathogenic avian influenza is a natural infection of waterfall that may cause minimal impacts or no signs of disease in domestic poultry and wild birds. So LPAI is not a serious threat. But on the other hand HPAI which is nothing but the highly pathogenic avian influenza it is a very serious one because it causes severe disease in domestic poultry and therefore it is associated with their high death rate. But know that HPAI is rarely found in waterfall. See to understand better have a look at this image here. In the first type it is the LPAI. See the pink color represents the infected organ and it is restricted to the intestine only. But when you take the next type that is the HPAI the pink color that is the infected region is almost covering the whole bird. And now you can understand the difference of severity between HPAI and LPAI. So far we saw about the basics of influenza, their types and we saw the sub types of avian influenza. Now how this virus is transmitted? Generally these viruses occur naturally among the wild birds. This we know already. So where does this virus reside? See the virus is present in the saliva, nasal secretions and feces of the infected wild birds. And the virus is spread to the other domestic birds that come in contact with these infected birds or the surfaces which are contaminated with the virus. This means open air markets where eggs and birds are sold in crowded and unsanitary conditions can lead to transmission of the virus. See I hope this video is helpful for you to understand about the influenza virus and its types and its mode of transmission. Now if you want to know more science related topics like this, subscribe to Shankarai's Academy's YouTube channel or watch the daily news analysis of Shankarai's Academy. Thank you.