A new study by University of Maryland researchers suggests that the potential for an avian influenza virus to cause a human flu pandemic is greater than previously thought and the results also illustrate how the current H1N1 swine flu outbreak likely came about.
Avian flu viruses can infect humans who have contact with birds but these viruses tend not to transmit easily between humans but in research recently published in the Proceedings of the National Academy of Sciences, Associate Professor Daniel Perez from the University of Maryland says that after reassortment with a human influenza virus, a process that usually takes place in intermediary species like pigs, an avian flu virus requires relatively few mutations to spread rapidly between mammals by respiratory droplets.
In his study, Perez used the avian H9N2 influenza virus, one that is on the list of candidates for human pandemic potential. Using reverse genetics, a technique whereby individual genes from viruses are separated, selected, and put back together, Perez and his team created a hybrid human-avian virus. Their research hybrid has internal human flu genes and surface avian flu genes from the H9N2 virus. Though it comes from a different strain of avian flu than the one that contributed to the hybrid virus now causing the swine flu outbreak, Perez's research virus is similar in origin to the swine flu virus, in that both involved a combination of avian and human influenza viruses.
Why the Type A virus can't be eradicated. Credit: University of Maryland
Perez infected ferrets (considered a good model for human influenza transmission) with the virus he created, and allowed the virus to mutate in the species. Before long, healthy ferrets that shared air space but not physical space with the infected ferret had the virus, showing that the virus had mutated to spread by respiratory droplets.
When the genetic sequences of the mutant virus and original hybrid virus were compared, the only differences were five amino acid mutations, three on the surface, and two internally. Two of the surface mutations were determined to be solely responsible for supporting respiratory droplet transmission. Because so few mutations were necessary to make the hybrid H9N2 transmissible this way, they concluded that after an animal-human hybrid influenza virus forms in nature, a human pandemic of this virus is potentially just a few mutations away.
Here, associate Professor Daniel Perez from the University of Maryland talks about the H9N2 virus.
"This is similar to the method by which the current swine influenza strain likely formed," said Perez, program director of the University of Maryland-based Prevention and Control of Avian Influenza Coordinated Agricultural Project, AICAP. "The virus formed when avian, swine, and human-like viruses combined in a pig to make a new virus. After mutating to be able to spread by respiratory droplets and infect humans, it is now spreading between humans by sneezing and coughing."
The Influenza A virus. Credit: University Of Maryland
However, scientists cannot predict what the actual mutations will look like if and when they occur in nature, or even which strain of avian influenza will mutate to infect mammals.
"This is just the tip of the iceberg," said Perez. "Many more studies have to be done to see which combinations of mutations cause this type of transmission before we can design the appropriate vaccines."
Perez will be talking this week with the NIH and the CDC to discuss his team's role in researching the current swine flu virus strain. Perez will likely do studies related to vaccine development, virus transmission between humans and animals, and the pathogenesis of the virus.
A virus vaccine is derived from the virus itself. The vaccine consists of virus components or killed viruses that mimic the presence of the virus without causing disease. These prime the body's immune system to recognize and fight against the virus. The immune system produces antibodies against the vaccine that remain in the system until they are needed. If that virus, or in some cases a closely similar one is later introduced into the system, those antibodies attach to viral particles and remove them before they have time to replicate, preventing or lessening symptoms of the virus.
The immune system also retains antibodies to a virus after being infected with it, so humans have general immunity to human strains of avian influenza strains. But humans do not generally have immunity to avian flu strains because they have not been infected by them before. The surface proteins are sufficiently different to escape the human immune response. Avian flu strains are therefore more dangerous for humans because the human immune system cannot recognize the virus or protect against it.
- PHYSICAL SCIENCES
- EARTH SCIENCES
- LIFE SCIENCES
- SOCIAL SCIENCES
Subscribe to the newsletter
Stay in touch with the scientific world!
Know Science And Want To Write?
- Quantum mechanics in 1834?
- Why This New "Planet X" Is No Threat To Earth :).
- Would New Planet X Clear Its Orbit? - And Any Better Name Than "Planet Nine"?
- The Greenhouse Effect Fallacy
- Native Americans Aren't More Prone To Alcoholism
- Top Secret: On Confidentiality On Scientific Issues, Across The Ring And Across The Bedroom
- The Doctor-Less Hospital Future
- "Thanks, didn't know about those. But it could also be a shower of hail stones, using the wikipedia..."
- "Are you saying that the sea level data are wrong? I'm just quoting it. If so, please note your data...."
- "For a good place to start, concerning causality as it relates to physics and the mathematics of..."
- "We are also biologically programmed to avoid death for as long as possible. Depends on what you..."
- " This is blatantly a false statement. Contrary to popular belief, CO2 is NOT the cause of temperature..."
- Moscow gets rid off aerosols
- Common gene variant influences food choices ... for better or worse
- Americans recognize 'past presidents' who never were, study finds
- A 'nudge' reduces doctors' unnecessary antibiotic prescription, study finds
- Penn Medicine 'brain road maps' reflect behavior differences between males and females