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¹Ù´ÙÇ¥¹ü Influenza·Î »ç¸Á °ü·Ã ÀÚ·á
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2016-04-28
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¹Ù´ÙÇ¥¹ü Influenza·Î »ç¸Á °ü·Ã ÀÚ·á
DIE-OFF, SEAL - USA (03): NEW ENGLAND, INFLUENZA ************************************************ A ProMED-mail post < http://www.promedmail.org> ProMED-mail is a program of the International Society for Infectious Diseases < http://www.isid.org>
Date: Tue 20 Dec 2011 Source: The Boston Globe [edited] < http://bostonglobe.com/metro/2011/12/20/flu-virus-linked-seal-deaths-off-new-england-coast/CGm1ytfcDbuxc0msgNnT9J/story.html>
A flu virus similar to one found in birds but not previously detected in harbor seals was the cause of 5 of 162 recent deaths of the marine animals off the New England coast, federal and state officials said yesterday [19 Dec 2011].
The influenza virus, known as H3N8, appears to have a low risk for transmission to humans, they said. But officials are urging the public to be cautious about approaching stranded seals to reduce the potential risk of spreading the infection to people or their unleashed dogs.
"Influenza that poses a risk to people are human strains of influenza, but there have been documented cases in people of transmission from other species," said Dr. Catherine M. Brown, public health veterinarian for the Massachusetts Department of Public Health.
Other viruses that caused global disease outbreaks in years past, such as avian and swine flu, jumped from birds and pigs to humans, usually through the animals' caretakers, Brown said. She said there have been an increasing number of instances in the past decade of flu viruses jumping from one species to another.
As Dr. Teri Rowles, a marine mammal coordinator at the National Oceanic and Atmospheric Administration's fisheries service put it: "We all understand the connectivity between wildlife health and human health and ocean health."
Federal scientists have been working with researchers from the New England Aquarium and various centers around the country to investigate the string of seal deaths since September 2011 along coastline stretching from Massachusetts to Maine.
Young harbor seals accounted for most of the deaths, which were coming at a pace roughly 3-4 times the normal number in September and October 2011, said Dr. Charles Innis, the aquarium's chief veterinarian. The death rate has slowed since late November 2011.
The specialists said in a press conference that they believe the influenza type A virus that infected the seals left them vulnerable to a bacterial pneumonia that killed 5 of them, all off New Hampshire's coast. They said that land-based animals such as wild birds that were infected suffered upper respiratory infections, and most recovered.
"We don't understand at the moment what is making this virus more deadly," said Dr. Hon Ip, a researcher at the US Geological Survey Wildlife Health Center. Ip said earlier deaths of seals have been traced to an influenza virus but that they were few and far between since the 1970s.
The scientists said they will continue to study the strandings and test tissue samples taken from some of the dead seals to determine how many others may have been infected by the virus.
So far, only harbor seals appear to have been affected, but the scientists said they will be investigating whether the virus has infected gray seals and harp seals, and they will be working with scientists in Canada to monitor the health of harbor seals in Canadian waters.
Some studies have indicated that certain contaminants can adversely affect marine mammals, such as polychlorinated biphenyls, or PCBs, a lubricant banned in the United States in the 1970s because of evidence it harmed fish and other wildlife. The substance is slow to break down and persists in the environment.
Rowles, the NOAA fisheries coordinator, said researchers have not seen any signs of a spike in PCB levels in the dead seals they have studied so far.
"That is something that, as we move forward, we will look for and test?" Rowles said, "but at this point, we have no evidence that there is something abnormal for PCB loads or other contaminants."
[Byline: Kay Lazar]
-- Communicated by: ProMED-mail <promed@promedmail.org>
[Influenza A viruses are classified according to subtypes that are a combination of 16 possible HAs (hamaglutinin) and 9 possible NAs (neuraminidase). All H3N8 viruses belong to the same subtype, but this does not necessarily mean they are the same virus. The fact that only 5 out of 162 stranded tested seals were positive suggests that this virus might not be the major health problem these seals are facing. Apparently, there is no evidence either that the virus is now "deadlier." In the past (1979-1983), influenza A virus was isolated from seals which had died from pneumonia in New England. It is relevant to establish whether other stranded animals also had pneumonia.
The interactive HealthMap/ProMED-mail map for New England is available at: <http://healthmap.org/r/1xMA>. - Mod.PMB]
[This appears to be the first time that A/(H3N8) influenza virus viruses have been associated with mortality in marine mammals. Influenza A(H3N8) virus is commonly associated with ducks and other wild aquatic birds. This may conceivably be a route of exposure of marine mammals such as seals to this virus, but it would be premature to assume this. Two other distinct groups of A/(H3N8) influenza viruses infect horses and dogs. Recent analyses of these viruses suggest that the canine and equine viruses are separately evolving groups. Rivailler et al. (Virology. 2010 Dec 5;408(1):71-9) have investigated the canine and equine influenza (H3N8) viruses co-circulating in the the USA during the period between 2005 and 2008. The genomes of the influenza A /(H3N8) viruses isolated from numerous dogs and horses were sequenced to determine their origin and evolution. Phylogenetic analyses revealed that the A/(H3N8) influenza viruses isolated from horses and dogs were monophyletic and distinct. There was no evidence of canine influenza virus infection in horses with respiratory disease or new introductions of equine influenza viruses into dogs in the United States. Analysis of a limited number of equine influenza viruses suggested substantial separation in the transmission of viruses causing clinically apparent influenza in dogs and horses. It may be that a distinct group of influenza A/(H3N8) viruses is already present in seal populations. Genomic analysis will help to resolve this issue. - Mod.CP]
[see also: Die-off, harbor seals - USA (02): New England, influenza 20111215.3607 Die-off, harbor seals - USA: northeast, influenza susp. 20111106.3301 Die-off, seal - USA: New England, RFI 20111027.3203 Die-off, marine wildlife - USA (02): (AK) seal, RFI 20111014.3074 Die-off, marine wildlife - USA: (NH) RFI 20111012.3052 Q fever - USA (02): (AK) seals 20110911.2771 2007 ---- Die-off, marine wildlife - USA (03): (AK) seal, walrus 20070518.1580 Die-off, seals - Kazakhstan (Mangistauskaya): RFI 20070418.1280 2003 ---- Phocine distemper virus, seals - UK 20030112.0099] .................................................pmb/msp/lm
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