16 Differences Between Antigenic Shift and Antigenic Drift

Biology Educational Videos

Last Updated on February 4, 2021 by Sagar Aryal

Differences Between Antigenic Shift and Antigenic Drift

Here are some differences:

S.N.CharacteristicsAntigenic ShiftAntigenic Drift
1.DefinitionAntigenic shift refers to the gene recombination occurring when influenza viruses re-assort.Mutations causing minute changes in the hemagglutinin and neuraminidase antigens on the surface of the Influenza virus is termed as antigenic drift.
2.Result inForms a new sub-type (Subtype A + Subtype B –> New Subtype).Forms a new strain of virus.
3.Genome changesLarge change in nucleotides of RNA.Small mutation of RNA.
4.Results fromGenome re-assortment between difference subtypes.Accumulation of point mutations in the gene.
5.Change typeThe change is sudden and drastic.The change is gradual.
6.Virus involvedOne or more viruses are involved.Only one virus is involved.
7.Magnitude of changeThe change is large at once.Changes increase with each division cycle.
8.Relatedness of new virusThe new form or subtype produced bears no similarity to the previous virus.The strains produced by antigenic drift are somewhat similar to the older strains.
9.Host rangeMay jump from one species to another, for instance animal to human.May infect animals of the same species only.
10.Frequency of occurenceOccurs once in a time.Occurs frequently.
11.Antigen changesThe virus acquires completely new antigens—for example by reassortment between avian strains and human strains.Antigens are only mutated.
12.Virus type involvedOccurs only in Influenza Virus AOccurs in Influenza Virus A, B and C
13.Leads toLeads to pandemics.Leads to mainly epidemics.
14.Treatment optionDifficult to treat (need new vaccine)Easy to treat (antibody and drugs available)
15.SusceptibilityEverybody is susceptible to the virus after an antigenic shift, and the novel influenza may thus spread uncontrollably.Some people may still be immune and some others may be partly immune to the new strain of virus thus leading to a milder illness.
16.ExamplesThe 1968 pandemic arose when the H3 hemagglutinin gene and one other internal gene from an avian donor reassorted with the N2 neuraminidase and five other genes from the H2N2 human strain that had been in circulation.

The 1918 pandemic arose when an avian H1N1 strain mutated to enable its rapid and efficient transfer from human-to-human.

The subtle mutations accumulated through antigenic drift of these subtypes (e.g., H1N1, H3N2, H5N1) give rise to different strains of each subtype.

Antigenic drift is also known to occur in HIV (human immunodeficiency virus), which causes AIDS, and in certain rhinoviruses, which cause common colds in humans. It also has been suspected to occur in some cancer-causing viruses in humans.

Read more about Antigenic Shift and Antigenic Drift from USMLE Step 1 Preparation videos and books.


  1. http://score99.blogspot.com/2009/05/influenza-antigenic-drift-and-shift.html
  2. http://www.usmleforum.com/files/forum/2009/1/470125.php
  3. https://microbiologyinfo.com/differences-between-antigenic-shift-and-antigenic-drift/
  4. https://www.globalsecurity.org/security/ops/hsc-scen-3_flu-antigenic.htm
  5. Lydyard, P.M., Whelan,A.,& Fanger,M.W. (2005).Immunology (2 ed.).London: BIOS Scientific Publishers.

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.