What Are The Common Flu Viruses?
Subtypes such as H1N1 influenza, H7N9 influenza, and H5N1 influenza are frequently reported. Also known as "human flu", " bird flu " and "swine flu", from different infected objects, refers to the flu that spreads in a specific group of animals. At the end of the day, whether it's poultry or swine, it's the flu. The causative agent belongs to the family Orthomyxoviridae, the influenza virus. However, this does not mean that avian influenza can only be transmitted in birds. With the mutation of the virus, the avian influenza virus has been detected in all mammals, and H7N9 is the ironclad evidence of human infection with avian influenza.
In 1997, 18 cases of human infection with H5N1 highly pathogenic avian influenza were discovered in Hong Kong, of which 6 died. This is the world's first case of H5 bird flu virus infection, which has sounded the alarm for humans. "Chicken plague" can become "human plague." Many people will wonder why people are not "birds" and are often infected with bird flu. Is it because our bodies are getting weaker?
Initially, avian influenza viruses were independent of human factors because influenza virus infection is host-specific. First, cells infected by the virus require specific receptors. Human-type influenza virus receptors are mainly distributed in the upper respiratory tract of humans. The "key" of the poultry influenza virus cannot open the door of human cells, so poultry influenza virus cannot infect humans Although human and avian influenza virus receptors are found to be distributed in the lower respiratory tract of humans at the same time, avian influenza viruses are more suitable for living in birds in a high-temperature environment. It exists in humans, just like people in the equatorial region go to the poles, the environment will suddenly change, and the vitality will no longer be strong. But now the bird flu virus is camping out in humans. One reason is that the flu virus has a special pattern of inheritance that keeps it mutating.
The genetic material of the influenza virus is single-stranded ribonucleic acid, which has poor stability. In addition, influenza virus RNA has a rather unreliable auxiliary RNA polymerase during replication, and newly synthesized daughter RNA often makes mistakes. It's like a group of careless students copying texts. After numerous replications, the final text has been separated from the original text by thousands of miles, which has led to the accumulation of virus mutations. In addition to the high mutation rate, the bird flu virus genome is composed of 8 small segments, which are easy to communicate with during the propagation process. Influenza viruses from other species rearrange themselves, increasing the chance of viral mutations. Through continuous mutation and selection, the poultry influenza virus has obtained the weapon to break through the city of human cells. Mutations are of course the basic condition for the transmission of poultry flu viruses to humans, but changes in human production activities are the source of nightmares.
For example, large-scale poultry farming by humans provides opportunities for close contact between humans and birds. In the long run, humans have become a new external environment for poultry influenza viruses. In this process, mutations suitable for human cells produced by bird influenza viruses can be easily screened and retained. The human body lacks antibodies against this new type of viral influenza virus, so they are often highly pathogenic and lethal after infecting the human body. However, to enhance the ability of human-to-human transmission, avian influenza still needs to break through many limiting factors. It is now known that H5 and H7 birds exist in natural influenza viruses, and no cases of human-to-human transmission have been found. Of course, once the virus mutates, it will be a nightmare for mankind.