Avian Influenza in Humans — A Matter of Time
Many experts think that an avian flu pandemic is on the horizon. It could be more deadly than the influenza epidemic of 1918 that killed more than 20 million people worldwide. While not completely proven, many scientists think that the 1918 flu outbreak in humans originated from a form of swine influenza that jumped to humans.
Daniel Perez, assistant professor of virology, at the University of Maryland (Virginia-Maryland Regional College of Veterinary Medicine) is a leader in research of and education on avian influenza. Dr. Perez uses a relatively new method of gene manipulation called plasmid-based reverse genetics to study how avian influenza strains are able to move to different species, including humans. He is also project director of the $5 million USDA-funded avian influenza research project, "Prevention and Control of Avian Influenza in the U.S.," based at the University of Maryland (www.agnr.umd.edu/aicap).
What do you think is the potential for human-human transmission of avian influenza?
Perez: "It has been good for us that avian influenza viruses have difficulties transmitting from human to human, but in my opinion, it's just a matter of time. There have been more incidents of avian influenza going to humans in recent years. Through different agricultural practices, humans have altered the ecosystem of many animal species, including poultry and swine, which have resulted in the creation of optimal conditions for the emergence of novel influenza virus strains. With worldwide poultry and swine production going up, the chances for another influenza pandemic appear imminent."
How do pigs figure in the transmission of avian flu to humans?
Perez: "Swine are intermediary hosts -- they are susceptible to both avian and human viruses. The H5N1 virus can adapt to intermediary hosts and stay in pigs and terrestrial birds for a long time. In China and S.E. Asia different avian species co-mingle with pigs and humans, which creates an optimal situation for the virus to adapt to humans. It only has to change a little bit."
Why not just eradicate the virus in the birds that carry it?
Perez: "We can't eradicate the virus as long as we have aquatic birds. It doesn't usually kill aquatic birds - they are the perfect host. The problem starts when it jumps into other species, like chickens and turkeys, that aren't natural hosts. They get the disease. As long as people have birds for food or pets, avian influenza will be a problem."
What is your research looking at?
Perez: "We are trying to determine how the influenza virus makes the jump from one species to another. We are attempting to map specific amino acid residues involved in interspecies transmission of the H9N2, H2N2, H7N3, and H5N1 influenza viruses, which are believed to have the greatest potential to become pandemic viruses."
What method are you using to study virus transmission?
Perez: "We use plasmid-based reverse genetics to manipulate the [influenza] genome in any way we want. We are talking about cloning a virus into units of DNA that we can mutate. I look at changes in the amino acids that might be important in transmission."
Why is education important in preventing a pandemic of avian influenza?
Perez: "My interest in this research is to make people aware that while understanding and preventing avian influenza is important in the poultry industry, it is also very important from a public health point of view. It's important for people to realize that they can't mix avian species, for example free range chickens, that could come in contact with other birds that carry the influenza virus."
Before coming to Maryland, Dr. Perez was in St Jude Children's Research Hospital where he played an active role in the development of the first vaccine for H5N1 influenza using plasmid-based reverse. The team rapidly developed the H5N1 vaccine using samples of H5N1 obtained from a patient in Hong Kong who died after being infected with the avian virus. Ultimately, Perez hopes that his research at Maryland will lead to a vaccine that prevents the inter-species transmission of influenza. At the very least, he says, the plasmid-based reverse genetics process has already allowed scientists to greatly speed up the process of developing certain vaccines for potentially pandemic forms of human influenza.
Contact: Lab, 301-314-6678, dperez1@umd.edu; or Ellen Ternes, 301-405-4627, eternes@umd.edu
Website: http://www.agnr.umd.edu/AGNRDirectory/Bio.cfm?ID=107377449 or www.agnr.umd.edu/avianflu
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Information provided by the Office of University Communications
