Avian flu research unravels why and how swine flu outbreak came about

April 30th, 2009 - 2:05 pm ICT by IANS  

New York, April 30 (IANS) A lethal avian flu virus can cause human flu pandemic more easily than previously thought, according to a new study.
University of Maryland (U-M) researchers have explored the mechanisms of how combined avian-human viruses are transmitted and how virus outbreaks like that of the current swine flu came about.

Daniel Perez, associate professor, U-M, showed that after an avian and human-like virus combine, the virus requires relatively few mutations to spread rapidly between mammals by respiratory droplets.

“This is similar to the method by which the current swine influenza strain likely formed,” said Perez,

“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.”

Generally, avian flu viruses infect birds, and human viruses infect humans. Because their immune systems “remember” what the viruses look like from previous exposures, humans and birds tend to have some level of immunity to their respective viruses.

Though avian flu viruses do sometimes infect humans and cause severe illness, these viruses do not transmit easily from human to human so the spread is rare.

A problem arises when an intermediary species that can host both avian and human-like viruses, such as a pig, is infected with both types of virus, said an U-M release.

In cases like these, the viruses can combine in the host to make hybrid avian-human viruses. These viruses can infect humans but escape the immune response because their surface proteins are foreign to the immune system. While these viruses can cause serious illness, they are generally not passed easily between humans.

However, Perez has shown that this type of virus can fairly easily mutate to spread quickly and potentially cause a human pandemic.

The study was published in the Proceedings of the National Academy of Sciences.

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