10. September 2009 05:39
http://www.news-medical.net/news/20090910/Swine-flu-more-lethal-than-seasonal-flu.aspx
Pandemic swine flu can infect cells deeper in the lungs than seasonal flu can, according to a new study published today in Nature Biotechnology. The researchers, from Imperial College London, say this may explain why people infected with the pandemic strain of swine-origin H1N1 influenza are more likely to suffer more severe symptoms than those infected with the seasonal strain of H1N1. They also suggest that scientists should monitor the current pandemic H1N1 influenza virus for changes in the way it infects cells that could make infections more serious.
Influenza viruses infect cells by attaching to bead-like molecules on the outside of the cell, called receptors. Different viruses attach to different receptors, and if a virus cannot find its specific receptors, it cannot get into the cell. Once inside the cell, the virus uses the cell's machinery to make thousands more viruses, which then burst out of the cell and infect neighbouring ones, establishing an infection.
Seasonal influenza viruses attach to receptors found on cells in the nose, throat and upper airway, enabling them to infect a person's respiratory tract. Today's research, which was funded by the Wellcome Trust, the Medical Research Council and the Engineering and Physical Sciences Research Council, shows that pandemic H1N1 swine flu can also attach to a receptor found on cells deep inside the lungs, which can result in a more severe lung infection.
The pandemic influenza virus's ability to stick to the additional receptors may explain why the virus replicates and spreads between cells more quickly: if a flu virus can bind to more than one type of receptor, it can attach itself to a larger area of the respiratory tract, infecting more cells and causing a more serious infection.
Professor Ten Feizi, a corresponding author of today's paper from the Division of Medicine at Imperial College London, said: "Most people infected with swine-origin flu in the current pandemic have experienced relatively mild symptoms. However, some people have had more severe lung infections, which can be worse than those caused by seasonal flu. Our new research shows how the virus does this - by attaching to receptors mostly found on cells deep in the lungs. This is something seasonal flu cannot do."
The researchers found that pandemic H1N1 influenza bound more weakly to the receptors in the lungs than to those in the upper respiratory tract. This is why most people infected with the virus have experienced mild symptoms. However, the researchers are concerned that the virus could mutate to bind more strongly to these receptors.
"If the flu virus mutates in the future, it may attach to the receptors deep inside the lungs more strongly, and this could mean that more people would experience serious symptoms. We think scientists should be on the lookout for these kinds of changes in the virus so we can try to find ways of minimising the impact of such changes," added Professor Feizi.
The researchers compared the way seasonal and pandemic H1N1 flu viruses infect cells by identifying which receptors each virus binds to. To do this, the researchers used a glass surface with 86 different receptors attached to it, called a carbohydrate microarray. When viruses were added to the glass surface, they stuck to their specific receptors and the corresponding areas on the plate 'lit up'. This meant the researchers could see which receptors the different viruses attached to.
Pandemic H1H1 influenza could bind strongly to receptors called α2-6, which are found in the nose, throat and upper airway, and it could also attach more weakly to α2-3 receptors, which are found on cells deeper inside the lungs. However, seasonal H1N1 influenza could only attach to α2-6.
"Receptor binding determines how well a virus spreads between cells and causes an infection," said Professor Feizi. "Our new study adds to our understanding of how swine-origin influenza H1N1 virus is behaving in the current pandemic, and shows us changes we need to look out for."
http://www3.imperial.ac.uk/
Zambian nurses contract swine flu
http://www.postzambia.com/content/view/13417/
TWO nurses at the University Teaching Hospital (UTH) who were attending to Swine flu patients have been diagnosed with the AH1N1 virus, Ministry of Healthspokesperson Dr. Rueben Mbewe has confirmed. The two are among the latest four cases identified to have the deadly Swine flu virus yesterday and adds to the earlier six cases which were reported on Monday this week.
Speaking in an interview this morning, Dr Mbewe said the total number of confirmed cases had now risen to 15 since July 23, 2009 when the first three cases were reported.
“We have received four more cases and among them are health providers, we have confirmed that one of them was attending to the patients while the other one must also have contracted the virus from the patients.” “This brings the total number of confirmed cases to 15,” he said.
Dr Mbewe said the spread of the virus was worrying because the new cases could not be linked to victims having recently travelled out side the country.
“The problem is that we can’t link these knew cases to having traveled abroad recently or having been in contact with swine flu patients who recently traveled. This means it is a local transmission of the virus and the recent six plus four cases are all from within Lusaka,” Dr Mbewe said.
He said from the previously diagnosed six patients, two had been discharged after recovering while the rest including the latest four victims had been quarantined for medication.
He further said the ministry was awaiting a third consignment of Tami-flu tablets which cures Swine flu from the World Health Organisation (WHO).
“We have intensified our sensitization programmes on TV and radio through adverts but we are also waiting for a third consignment of Tami-flu. A lab has been set up at UTH which is handling the cases,” he said.
Zambia recorded the first five cases in July through Copperbelt University Students and lecturer who returned from a sports tournament in Belgrade.
Thanks for the update, DvdMom
Ping.