Endemic influenza by estimates causes 500.000 deaths each year, in particular among young children and the elderly . Three distinct viral types (A, B and C) circulate in the human population. While types B and C evolve slowly and circulate at low levels, influenza A through rapid evolution continuously evades host immunity from previous infection or vaccination and regularly causes large epidemics. The virus is a single-stranded, negative-sense RNA virus of the family Orthomyxoviridae. The antigenic properties of a specific virus are defined by the surface glycoproteins, haemagglutinin (HA) and neuraminidase (NA). These proteins are under ongoing selection for change and continuously acquire mutations which result in reduced immune recognition in previously infected or vaccinated hosts -- a process referred to as antigenic drift.
Immunity can be achieved either by infection or vaccination, but is non permanent, due to the rapid evolution of the virus. Accordingly, the composition of influenza vaccines is updated annually, following suggestions of the World Health Organization. Although a successful match to the dominant circulating strain is achieved in the majority of cases, there is still room for improvement. Using statistical modeling and theoretical simulations with a stochastic epidemiological model, we are investigating the short-term evolutionary dynamics of the virus to identify further molecular determinants of viral fitness with relevance to vaccine strain selection.
Dirk Hoeper and Michael Beer, Institute of Diagnostic Virology, Friedrich-Loeffler-Institut, Greifswald - Insel Riems, Germany
Juergen and Olga Stech, Institute of Molecular Biology, Friedrich-Loeffler-Institut, Greifswald - Insel Riems, Germany
Influenza - WHO cares
The Lancet Infectious Diseases 2002, 2(9):517
B. Adams, A.C. McHardy, C. Lundegaard, T. Lengauer
To appear in: Modern Genome Annotation D. Frishman, A. Valencia (Editors), Springer Verlag, NY
A.C. McHardy and B. Adams
The role of genomics in tracking the evolution of influenza A virus.
PLoS Pathogens 2009, October,26 5(10): e1000566. doi:10.1371/journal.ppat.1000566