Different types of avian influenza virus

There are three main types of avian influenza virus, but not all of them pose a threat to human beings Influenza A virus is a type of virus that infects and spreads between birds and has many branches Although all of these branches occur in birds, there are a few that can affect humans The most common type in humans is H9 (hemagglutinin 9) H5 (haemagglutinin 5) has branches that can cause death in humans, but it is rare Human infection with H7 (hemagglutinin 7) usually occurs in contact with sick birds, rather than interpersonal transmission The subcategory of avian influenza viruses is defined by a mixture of the second letter and number after the first group The first number defines the amount of hemagglutinin protein contained in the virus, and the second number defines the neuraminidase (n) protein Most H5 avian influenza viruses have many different genetic variations, expressed in n One of the powerful avian influenza viruses that can be transmitted to humans is the H5N1 strain The bird flu has a high mortality rate in humans (the first infection occurred in Hong Kong in 1997) The virus can cause typical flu symptoms, such as fever, body pain, fatigue and weakness In some cases, it can also cause organ and respiratory failure The development of the virus in humans confirms that influenza can mutate and spread through different species Avian influenza A virus is so named because each type and subclass is found in birds Some subcategories are lethal to birds, especially domesticated poultry All H5 subclasses have been recorded in humans, but H7 and H9 rarely occur in humans and are usually mild If it happens in birds, there are two types of bird flu outbreaks Some viruses simply cause birds to look unhealthy, changing the number and quality of eggs laid, but can be deadly when they mutate and spread to humans Other types, also known as high pathogenicity, can cause a large number of deaths in poultry Once a species is infected with one of the subcategories of avian influenza, the disease usually spreads quickly.