The Influenza Flu Virus Next to the common cold, influenza or "the flu" is perhaps the most familiar respiratory infection in the world. In the United States alone, approximately 25 to 50 million people contract influenza each year. The symptoms of the flu are similar to those of the common cold, but tend to be more severe. Fever, headache, fatigue, muscle weakness and pain, sore throat, dry cough, and a runny or stuffy nose are common and may develop rapidly.
Clade 2 viruses were first identified in bird isolates from ChinaIndonesiaJapanand South Korea before spreading westward to the Middle EastEuropeand Africa. The clade 2 viruses have been primarily responsible for human H5N1 infections that have occurred during late andaccording to WHO. Genetic analysis has identified six subclades of clade 2, three of which have a distinct geographic distribution and have been implicated in human infections: Before our project, GenBank contained only 5 other complete genomes from Europe for the — period, and it contained no whole genomes from the Middle East or northern Africa.
Our analysis showed several new findings. First, all European, Middle Eastern, and African samples fall into a clade that is distinct from other contemporary Asian clades, all of which share common ancestry with the original Hong Kong strain.
Phylogenetic trees built on each of the 8 segments show a consistent picture of 3 lineages, as illustrated by the HA tree shown in Figure 1. Two of the clades contain exclusively Vietnamese isolates; the smaller of these, with 5 isolates, we label V1; the larger clade, with 9 isolates, is V2.
The remaining 22 isolates all fall into a third, clearly distinct clade, labeled EMA, which comprises samples from Europe, the Middle East, and Africa. Trees for the other 7 segments display a similar topology, with clades V1, V2, and EMA clearly separated in each case.
A stands for the genus of influenza AB or C. N1 stands for the first of several known types of the protein neuraminidase.
The distinction concerns pathogenicity in poultry, not humans. Normally, a highly pathogenic avian virus is not highly pathogenic to either humans or nonpoultry birds. This current deadly strain of H5N1 is unusual in being deadly to so many species, including some, like domestic cats, never previously susceptible to any influenza virus.
HA codes for hemagglutininan antigenic glycoprotein found on the surface of the influenza viruses and is responsible for binding the virus to the cell that is being infected.
NA codes for neuraminidasean antigenic glycosylated enzyme found on the surface of the influenza viruses. It facilitates the release of progeny viruses from infected cells.
The Influenza (Flu) Virus In particular, the mixing of strains that can infect birds, pigs, and humans is thought to be responsible for most antigenic shifts. Notably, in some parts of the world, humans live in close proximity to both swine and fowl, so that human strains and bird strains, may readily infect a pig at the same time. Bird flu viruses infect birds, including chickens, other poultry, and wild birds such as ducks. Usually bird flu viruses only infect other birds. It is rare for people to . H7N9 is a strain of flu virus that normally infects birds but has spread to at least humans in a number of outbreaks related to poultry markets.
HA and NA are also used as the basis for the naming of the different subtypes of influenza A viruses. This is where the H and N come from in H5N1.
Influenza A viruses are significant for their potential for disease and death in humans and other animals. Influenza A virus subtypes that have been confirmed in humans, in order of the number of known human pandemic deaths that they have caused, include: H1N1which caused the flu pandemic "Spanish flu" and currently is causing seasonal human flu and the flu pandemic " swine flu " H2N2which caused "Asian flu" H3N2which caused "Hong Kong flu" and currently causes seasonal human flu H5N1" bird flu "which is noted for having a strain Asian-lineage HPAI H5N1 that kills over half the humans it infects, infecting and killing species that were never known to suffer from influenza viruses before e.
In most cases, it causes minor sickness or no noticeable signs of disease in birds. It is not known to affect humans at all. The only concern about it is that it is possible for it to be transmitted to poultry and in poultry mutate into a highly pathogenic strain.Infected birds shed avian influenza virus in their saliva, mucous and feces.
Human infections with bird flu viruses can happen when enough virus gets into a person’s eyes, nose or mouth, or is inhaled. The new research reveals that cells with H5N1 avian flu receptors are prevalent deep in the lungs of people who have died from infection, usually after direct contact with infected birds.
The Influenza (Flu) Virus In particular, the mixing of strains that can infect birds, pigs, and humans is thought to be responsible for most antigenic shifts. Notably, in some parts of the world, humans live in close proximity to both swine and fowl, so that human strains and bird strains, may readily infect a pig at the same time.
Influenza A infects mostly humans and birds, though it also affects pigs. Prolonged and close interaction between humans and other animals, such as chickens, allow for the virus to mutate and jump from species to species.
H7N9 is a strain of flu virus that normally infects birds but has spread to at least humans in a number of outbreaks related to poultry markets. Oct 08, · Scientists predict that the next influenza pandemic -- most likely to be a strain of bird flu that infects humans and spreads rapidly across the world via air travel -- could kill up to