What is shift and drift in influenza?

What is shift and drift in influenza?

Influenza strains are constantly mutating. A small change to the genetic makeup of influenza strains is referred to as antigenic drift, while a major change is called antigenic shift.

What is the difference between antigenic drift and antigenic shift in the influenza virus?

Antigenic drift vs. shift. Antigenic drift creates influenza viruses with slightly modified antigens, while antigenic shift generates viruses with entirely new antigens (shown in red).

Why does antigenic shift only occur in influenza A?

Antigenic shift, however, occurs only in influenza A because it infects more than just humans. Affected species include other mammals and birds, giving influenza A the opportunity for a major reorganization of surface antigens.

What is a shifting antigen virus?

Antigenic shift refers to the complete replacement of the HA or NA with a novel HA or NA. These viruses are “new” viruses to which the population has no specific immunity. When such a new virus is introduced into a population, a severe, worldwide epidemic, or pandemic, of influenza can result.

What is the significance of antigenic drift?

Antigenic drift allows for evasion of these host immune systems by small mutations in the hemagglutinin and neuraminidase genes that make the protein unrecognizable to pre-existing host immunity. Antigenic drift is this continuous process of genetic and antigenic change among flu strains.

What causes antigenic drift?

Antigenic drift: A subtle change in the surface glycoprotein (either hemagglutinin or neuraminidase) caused by a point mutation or deletion in the viral gene. This results in a new strain that requires yearly reformulation of the seasonal influenza vaccine.

What is the meaning of antigenic?

(AN-tih-jen) Any substance that causes the body to make an immune response against that substance. Antigens include toxins, chemicals, bacteria, viruses, or other substances that come from outside the body.

How antigenic shift occurs in influenza A virus?

Due to a segmented genome, influenza virions are capable of exchanging segments between virus strains. This genomic shuffling occurs when two or more different strains or subtypes infect the same cells in a host. This phenomenon is called antigenic shift.

What is antigenic shift with example?

An example of a pandemic resulting from antigenic shift was the 1918-19 outbreak of Spanish Influenza. This strain was originally the H1N1 avian flu, however antigenic shift allowed the viral infection to jump from pigs to humans, resulting in a large pandemic which killed over 40 million people.

Does antigenic shift only occur in influenza viruses?

Antigenic shift or reassortment variations occur only in influenza A viruses, which are sudden and complete changes in one or both surface antigens. This results completely in new viruses having surface antigens different from the antigens of the old viruses circulating in the population.

Is antigenic shift recombination?

Antigenic shift refers to the emergence of a novel influenza virus in humans, due to direct introduction of an avian strain or to a new strain produced by recombination and reassortment of two different influenza viruses.

Is antigenic drift responsible for pandemics?

The emergence of a new strain of influenza A due to antigenic drift can cause an influenza epidemic or pandemic.