Search results
Results from the WOW.Com Content Network
Immunity can be acquired either actively or passively. Immunity is acquired actively when a person is exposed to foreign substances and the immune system responds. Passive immunity is when antibodies are transferred from one host to another. Both actively acquired and passively acquired immunity can be obtained by natural or artificial means.
Biologists at Fred Hutchinson Cancer Research Center discovered that a single mutation in a flu virus can give it the power to escape 90% of one person’s antibody immunity, but not another’s.
These pandemics, in contrast to seasonal influenza, are caused by antigenic shifts involving animal influenza viruses. To date, all known flu pandemics have been caused by influenza A viruses, and they follow the same pattern of spreading from an origin point to the rest of the world over the course of multiple waves in a year.
An individual's immunity can be acquired via a natural infection or through artificial means, such as vaccination. [51] When a critical proportion of the population becomes immune, called the herd immunity threshold (HIT) or herd immunity level (HIL), the disease may no longer persist in the population, ceasing to be endemic. [5] [26]
What are the different types of influenza virus? There are four different types of influenza virus: A, B, C, and D. Influenza C usually causes only mild illness while D mostly affects animals ...
Antigenic drift is a kind of genetic variation in viruses, arising from the accumulation of mutations in the virus genes that code for virus-surface proteins that host antibodies recognize. This results in a new strain of virus particles that is not effectively inhibited by the antibodies that prevented infection by previous strains.
However, more recent research suggests the 1918 pandemic was caused by the antigenic drift of a fully avian virus to a form that could infect humans efficiently. [ 7 ] [ 8 ] The most recent 2009 H1N1 outbreak was a result of antigenic shift and reassortment between human, avian, and swine viruses.
Mammalian influenza viruses tend to be labile, but they can survive several hours in a host’s mucus. [57] Avian influenza virus can survive for 100 days in distilled water at room temperature and for 200 days at 17 °C (63 °F). The avian virus is inactivated more quickly in manure but can survive for up to two weeks in feces on cages.