Issues addressed included the growing body of evidence linking the origin of antigenic shift to animal reservoirs of influenza viruses (24), the questionable validity of predictable patterns of pandemic periodicity, and the appropriate classification of the 1947 strain (25).
No precedent existed for defining a pandemic strain or distinguishing antigenic shift (a complete change) from antigenic drift (point mutations resulting in accumulated amino acid changes).
Protection Against Antigenic Drift and Antigenic Shift
Antigenic shift occurs when there is exchange of genetic material between flu virus subtypes, creating an entirely new and potentially pandemic viral strain.
Francis died in 1969 and did not live to know the full explanations for antigenic shift
through reassortment of gene segments from 2 parent viruses or antigenic drift through mutation.
In the 20th century, the sudden emergence of autigenically different strains transmissible in humans, termed antigenic shift
, has occurred on four occasions, each time resulting in a pandemic.
Influenza vaccine--outmaneuvering antigenic shift
Similarly, pandemic strains of influenza developed through an antigenic shift
from avian influenza A viruses.
Surveillance of circulating viruses is increasing and flu vaccination has entered the mainstream, but epidemics are still frequent and strains arising from antigenic shift
keep the next flu pandemic just around the corner.
DNA polymorphism analysis of prn and ptxS1 has previously been used as a typing method for detecting antigenic shifts (2,3,8).
Our results suggest that ptxS1 is not a useful marker in outbreaks to detect antigenic shifts.