Subscribe
H3N2 flu virus (Courtesy www.primidi.com)
Each year, somewhere between five and 15 percent of the world’s population becomes infected during influenza A epidemics. These flu outbreaks are linked to as many as a half a million deaths annually, according to WHO. While vaccinations can be effective, influenza viruses often evolve so rapidly that creating effective vaccines can be difficult.
WHO’s Global Influenza Surveillance Network — consisting of more than 100 labs in 80 countries — tracks influenza virus evolution in order to try to decide which strains should be used in seasonal vaccines. But the data can also contribute to a better understanding of influenza evolution and spread in general.
Two flu studies have recently been published identifying the evolution and dispersal of the flu virus.
The first study found that flu outbreaks follow a predictable path around the world starting in East and Southeast Asia.This study focused on one of eight regions of the flu genome, HA, which codes for a surface protein hemagglutinin targeted by the human immune system. The results suggest that new strains usually begin in East and Southeast Asia, where they circulate continuously. These “seed” other outbreaks by proceeding first through Oceania, then Europe and North America, and eventually South America. But the paper indicates that viruses hardly ever go back in the other direction.
The second paper used comparative genomics to assess the evolutionary dynamics of H3N2 and another influenza A strain, H1N1. These researchers also suggest that influenza A strains in one region seed outbreaks in the rest of the world, following a “source-to-sink” pattern, though this research didn’y implicate Asia — but rather tropics in general — as the source. Southern China was proposed as the epicenter of influenza A virus but it is possible that tropical regions generally represent ideal source populations because of viral transmission.
Elaine Warburton www.geneticsandhealth.com
Comments
Post a comment