and increased incidence of meningococcal disease.
This news was greeted with controversy and has had to be subsequently justified in terms of developing defences against such an antigenic shift
occurring in the wild.
is a major and abrupt genetic reassortment, made possible when two subtypes exchange genetic material.
results when a new Influenza A subtype to which most people have little or no immune protection infects humans.
It is possible that cross-species transmission could lead to an antigenic shift
, whereby avian and human strains of influenza virus that are circulating at the same time swap genetic material, resulting in a novel, more virulent subtype.
is caused by a major reassortment of the genome, in which 2 different influenza A viruses, one human and one avian, each with a different hemagglutinin, infect a common host with resulting transfer of genetic material.
More rarely, about every 25 years on average, a more serious antigenic shift
occurs involving an exchange of gene segments between human and avian influenza viruses.
Both antigenic shift
, involving minor antigenic changes in the HA and NA glycoproteins, and antigenic drift, involving major changes, have been described.
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