As fast as we rev up a strong defense, they change to evade those defenses, upping the ante for either our bodies or our drugs.
However, HA can change to evade previously acquired immunity either by antigenic drift, whereby mutations of the currently circulating HA gene disrupt antibody binding, or by antigenic shift, with the virus acquiring an HA of a new subtype by re-assortment of one or more gene segments.
That's what happens in the animal kingdom: a school of fish changes direction to evade a predator, for instance.
HA changes antigenically to evade the immune response and on average, the prevalent influenza strains in circulation will acquire three to four amino acid changes per year in HA, mostly in regions of HA that are recognized by protective antibodies.
An investigation found some of the immigrants hid their identities and changed residences to evade federal authorities, a spokesman said.
Because of the tight coupling between the brain and the nerves surrounding the chromatophores, this remarkable transformation happens at lightning speed, allowing wild cuttlefish to quickly change colour to evade predators, sneak up on prey, or attract mates.
Árni Páll Árnason of the Social Democratic Alliance said the coalition was "trying to cling on to power while making the absolute minimum of changes, in order to evade the public".
During all stages of tumor progression, cancer cells are subjected to inappropriate extracellular matrix environments and must undergo adaptive changes in order to evade growth constraints associated with the loss of matrix attachment.
This strategy needs to be followed since hemagglutinin and neuraminidase are under selective pressure and undergo frequent antigenic changes in order to evade the host's immune system [ 4].
Results showed that the best way to include traffic jam avoidance is to assume that 10% of the drivers change their route to evade congested roads.
