The primary distinction between antigenic drift or antigenic change is the fact that antigenic drift is a way to create change in viruses that is caused by the accumulation of mutations in genes that encode for antigen-binding sites, whereas antigenic shift is a method of combining two kinds of viruses to create one new type that has an assortment of surface antigens of the viruses that were originally.

The antigenic and the hypogenic are both of the processes utilized by viruses to adjust to the pressure of selection and to evade the immune system of the host. Antigenic drift is a small antigenic change that results in an entirely new strain of virus while the antigenic shift represents an important antigenic change which results in a new type of virus.

What is Antigenic Drift?

An antigenic shift is gradual alteration in the viral gene caused by mistakes in replication as well as random changes. In the end, it creates the creation of a new strain of virus. In general, the antigenic drift within the genes that code for antigen-binding sites reduces the effectiveness of antibodies made to fight the earlier antigens. This makes spreading the disease within the host less likely. Thus, antigenic drift causes loss of immunity, as well as the mismatch of vaccines.

Additionally, antigenic drift is observed in the Influenzavirus A B, C. In essence, Influenza virus has two proteins that function as antigens for the surface. They are neuraminidase and hemagglutinin. In this case, hemagglutinin plays a role for adhesion and entry into host epithelial cells , while Neuraminidase plays a role in the formation of generating new virions out from host cell. The sites that these proteins recognize by the immune system of the host are subject to constant pressure from the host immune system. However, minor changes to these proteins caused by antigenic drift are able to bypass the immune system of the host.

What is Antigenic Shift?

Antigenic shift is a swift and massive antigenic shift in an infection. It typically is required for two different strains of virus to be combined to create an entirely new subtype of virus. The new type of virus has a mix of antigens on the surface in the original strains. Particularly, it is one of the types of reassortment that also results in the phenotypic changes.

In addition there is the possibility that Influenzavirus A is one of the viruses that undergoes an antigenic change. In normal circumstances, it affects not just humans however, but also birds, mammals and other animals. This virus also can reorganize its antigens on the surface when two varieties of the virus are infected with the same host. This is accomplished through the elimination of capsids and envelopes, and exposing their RNA for transcription. It permits the viruses to mix.

Similarities Between Antigenic Drift and Antigenic Shift

• Two methods utilized by viruses to adjust to selection pressures and to evade the immune system of the host.
• Both of these mechanisms alter the number of antigens present that comprise the virus in its original form.
• The resulting virus can’t be stopped by antibodies against the previous strains, which makes it easier for them to infect an immune-compromised population.

Differences Between Antigenic Shift and Antigenic Drift – Antigenic Shift vs Antigenic Drift

Characteristics	Antigenic Shift	Antigenic Drift
Definition	Antigenic shift is the mutation of genes that occurs when influenza viruses merge.	Changes in the DNA that cause tiny changes to the antigens of hemagglutinin or neuraminidas in the outer layer of Influenza virus are referred to as antigenic drift.
Result in	Forms a new sub-type (Subtype A + Subtype B -> New Subtype).	New strains that is a new strain of virus.
Changes to the genome	A large change in the nucleotides of RNA.	Small mutation in the RNA.
Results from	Genome re-assortment between different subtypes.	Point mutations accumulate within the gene.
Change the type	The shift is abrupt and dramatic.	The changes are gradual.
The virus in	A virus or several viruses are involved.	One virus is the only one involved.
Change in magnitude	The effect is huge all at once.	The changes increase with each cycle of division.
The connection between the new virus and its predecessor	The subtype or new version created is not akin to the virus that was previously in use.	The strains that are produced by antigenic drift look similar to the strains that were previously produced.
Host range	Can jump from one animal specie to the next, for example from animal to human.	It is possible to infect animals belonging to the same species, but only.
Frequency of the occurrence	Sometimes, it happens.	It is often seen.
Antigen changes	The virus develops entirely new antigens, for example through an amplification of avian strains as well as human strains.	Antigens can only be mutated.
Type of virus of virus	It is only found in Influenza Virus. A	Occurs in Influenza Virus A, B, and C
Leads to	This can lead to pandemics.	Causes major epidemics.
Treatment option	Very difficult for treatment (need the development of a vaccine)	Simple for treating (antibody and medications available)
Susceptibility	Everyone is vulnerable to the virus following an antigenic shift. novel influenza could be able to spread rapidly.	There are some who may be immune, while others could be in a partial immune to the latest virus strain, leading to a milder form of illness.
Examples	The pandemic of 1968 began due to the H3 hemagglutininin hemagglutin as well as a second inside gene extracted from an avian donor were reassorted with the N2 neuraminidase gene and five other genes of the H2N2 human strain which were in circulation.The 1918 pandemic was triggered after an avian H1N1 strain was altered to facilitate its rapid and effective transmission from humans to.	The minor mutations that have been accumulated over the course of antigenic drift in those subtypes (e.g. H1N1, H3N2, and H5N1) result in distinct strains of each subtype.Antigenic drift has also been found to be present also in HIV (human immune deficiency virus) which is the cause of AIDS and also in certain rhinoviruses, that cause common colds among humans. It has also been speculated to be present in certain cancer-causing viruses in humans.