"We now know where the influenza A virus comes from every year," said Edward Holmes, professor of biology at Penn State. "And because we now know how the virus evolves, we have a much better chance of controlling it."
Currently, there are many strains of the influenza virus that appear only in birds, which are natural viral reservoirs. So far three of these viral strains -- H1N1, H2N2 and H3N2 – have caused epidemics in humans as influenza A.
Of the three, H3N2 is the dominant strain, responsible for most influenza infections each winter, with lower levels of H1N1. However, little is known about how these two strains spread on a geographical scale, and how whole genome of influenza A virus evolves.
Holmes and his colleagues analyzed complete genomes of 1,032 strains of H1N1 and H3N2 viruses sampled over a 12-year period from New York state in the northern hemisphere and New Zealand in the southern hemisphere.
The researchers noticed that over time, both strains follow a distinctive pattern. In seasons where the H3N2 strain is dominant, H1N1 is not and vice versa.
"We found that the two strains peak at different times, and seem to be directly competing with each other" said Holmes, whose findings appear today online in Nature. The results also indicate that compared to the H3N2 strain, the H1N1 strain exhibits far less genetic diversity, although it is not clear why.
Holmes says his results also show that the influenza A virus is frequently exchanging genes by reassortment – when multiple human influenza viruses infect a single person and shuffle their genes – which sometimes allows the virus to acquire a new haemagglutinin, a protein that facilitates the entry of viral particles into the host cells.
These new haemagglutinins sometimes cause vaccines to fail, explained Holmes, whose work is funded by the National Institutes of Health.
"The critical thing is unless you understand the way the genome evolves, you will not understand why vaccines work during some years and fail during others," he added. "We can now show that vaccines failed in some years because new haemagglutinins appeared."
The Penn State researcher says his analysis not only indicates how the influenza virus is evolving, but also where new strains are being generated.
Each year new strains appear in the northern hemisphere, infect people and then burn out. However, patterns of genetic diversity within the viruses suggest the strains are coming from a global source population. The researchers believe that there must be some reservoir somewhere that every year generates new strains that are injected each season into the north and the south, and then burn themselves out.
"We know the strains are dying out every year in the northern and southern hemispheres. So they're surviving somewhere else, and we think it is a reservoir in the tropics," Holmes said. "It tells us that to really understand how the influenza virus evolves on a seasonal basis, and to make the best vaccine, we need to focus our surveillance on the source population in the tropics, especially in places such as Southeast Asia."
Amitabh Avasthi | EurekAlert!
How cancer metastasis happens: Researchers reveal a key mechanism
19.01.2018 | Weill Cornell Medicine
Researchers identify new way to unmask melanoma cells to the immune system
17.01.2018 | Duke University Medical Center
On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.
We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...
What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...
For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.
Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...
At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.
No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...
Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.
Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...
08.01.2018 | Event News
11.12.2017 | Event News
08.12.2017 | Event News
19.01.2018 | Materials Sciences
19.01.2018 | Health and Medicine
19.01.2018 | Physics and Astronomy