Antigenic shift, which is seen only with influenza A viruses, results from the replacement of the hemagglutinin and sometimes the neuraminidase with novel subtypes that have not been present in ...

Due to its segmented nature, influenza viruses can swap whole sections of their genome. If the segment swapped encodes an influenza antigen (such as HA or NA) which is targeted by the host immune ...

In 1958, a new strain of influenza A with different HA and NA was identified and antigenic shift was discovered; the need for a trivalent vaccine was recognized.

1918-19 "Spanish flu" A -- Caused the highest known influenza-related mortality: almost 700,000 deaths occurred in the U.S., and between 50 million to 100 million worldwide 1957-58 "Asian flu" A ...

The challenge: any universal influenza A vaccine has to successfully account for both antigenic drift and antigenic shift. So far, this has proven very difficult.

When antigenic shift happens, people often have little to no immunity. The constant evolution of the influenza virus continues to spark pursuit of combination antiviral therapy.

AP PhotoOver the past 60 years, the influenza virus has continued to drift and shift. In 1968 , a shift once again caused a pandemic. In 1976 and 2009 , concerns that the virus had shifted led to ...

Antigenic shift is a sudden alteration of a hemagglutinin or neuraminidase; antigenic drift is the backdrop of continual mutation. Strain A shifts and drifts; B and C only drift. "I had a birdy, his ...

Over the past 60 years, the influenza virus has continued to drift and shift. In 1968 , a shift once again caused a pandemic. In 1976 and 2009 , concerns that the virus had shifted led to fears ...

Antigenic Drift vs Antigenic Shift Even with careful research, a certain amount of educated guesswork is involved for manufacturers who select strains to incorporate into the annual flu vaccine.

The influenza A strain has been known to regularly change its antigenic properties, either through minor changes (antigenic drift) or through major changes (antigenic shift).

AP PhotoOver the past 60 years, the influenza virus has continued to drift and shift. In 1968 , a shift once again caused a ...