July 31, 2012

New Avian Flu Jumps To Mammals And Kills Seals

Brett Smith for - Your Universe Online

A new strain of avian influenza has be blamed in the deaths of over 160 seals off the New England coast last year, sparking fears that the virus, or one like it, could spread to other animals, including humans.

The majority of the dead harbor seals were less than six months old and an anatomical and microbiological analysis showed that these animals suffered from lesions and severe pneumonia, according to a report published in mBio, the online open-access journal of the American Society for Microbiology.

The appearance of dead seals from coastal Maine to Massachusetts in September 2011 raised concerns from scientists at Columbia´s Center for Infection and Immunity. Along with marine biologists at several other institutions, the CII scientists screened the animals for pathogens and found a new strain of the avian influenza virus was identified as seal H3N8.

"When initial tests revealed an avian influenza virus, we asked the obvious question: how did this virus jump from birds to seals?" said lead author Simon Anthony, a research scientist at the CII.

A complete genome sequencing and phylogenetic analysis showed that the new virus strain derived from an avian influenza strain that has been infecting the North American waterfowl population since 2002, according to the report.

Scientists examined the genome for any evidence of enhanced virulence. They found that the seal H3N8 virus can bind to sialic acid receptors found in the mammalian respiratory tract. This characteristic, along with the recent history of mammalian influenza viruses being spread to humans, means the new strain could pose a threat to public health, the study´s authors said.

In 2009, "swine flu", or H1N1, virus that emerged in humans was found to be the result of a combination of flu viruses found in birds, pigs, and humans. The results of this latest report suggest that the H3N8 strain in New England harbor seals could preclude a new group of influenza viruses with the ability to transmit among species.

"There is a concern that we have a new mammalian-transmissible virus to which humans haven't been exposed yet. It's a combination we haven't seen in disease before," said study editor Anne Moscona of Weill Cornell Medical College in New York City.

Moscona emphasized the study raises two concerns about the new flu virus. First, this strain is a novel virus with several traits that make it a prospective threat to both the human and animal populations. Second, the possibility of a bird flu virus strain that can infect seals hasn´t been widely researched or considered before, showing that a pandemic influenza could manifest in unexpected ways.

"Flu could emerge from anywhere and our readiness has to be much better than we previously realized. We need to be very nimble in our ability to identify and understand the potential risks posed by new viruses emerging from unexpected sources," says Moscona.

"It's important to realize that viruses can emerge through routes that we haven't considered. We need to be alert to those risks and ready to act on them."