Type A is likely to undergo an antigenic shift
if two or more subtypes infect a single host, creating new subtypes based on surface antigens hemagglutinin (H) and neuraminidase (N).
"The last epidemic caused by antigenic shift
was in 1989/90 and killed 29,000 people in Britain.
To make the person-to-person leap, the virus would need to undergo a molecular "change of clothes," a dramatic process known as an antigenic shift
. Like other flu viruses, A(H5N1) is made up of eight chromosomes, or strands of genetic material.
The abrupt changes in influenza A viruses commonly arise when genome segments reassort, sometimes acquiring new surface protein genes from animal sources, leading to antigenic shift
as was seen in the recent influenza A(H1N1) pandemic strain (5).
The influenza virus has the capacity for antigenic shift
through its ability to reassert with other influenza virus strains.
As populations have no immunity to the new subtype, and as no existing vaccines can confer protection, antigenic shift
has historically resulted in highly lethal pandemics.
One of the factors causing the latter problem is that the influenza virus is highly adaptive and does some minor structure changing every year (antigenic drift) and major changing every few years (antigenic shift
The predominant H3N2 variant has been "uncharacteristically" stable over the last few years and a significant antigenic shift
is anticipated, Dr.
The problem is that the predominant H3N2 variant has been "uncharacteristically" stable over the last few years and a significant antigenic shift
is anticipated, Dr.
The reemergence in 2012 of W135/ST11 strains that had the FetA1-1 marker suggests an antigenic shift
that may have involved membrane proteins other than FetA or other surface structures, such as the lipooligosasccharide.
, which is seen only with influenza A viruses, is a more drastic change.
After an interpandemic interval >35 years, any antigenic shift
may again seriously affect young adults, including many pregnant women.