Swine Flu Deaths Show This Flu Is Different

[indigo girl]

http://uk.reuters.com/article/idUKTRE58E7Q220090915?rpc=401&

Autopsies on people who have died from the new pandemic H1N1 flu show this virus is different from seasonal influenza, even if it has not yet caused more deaths, experts told a meeting on Tuesday.

Americans who died from swine flu had infections deep in their lungs, Dr. Sherif Zaki of the U.S. Centres for Disease Control and Prevention told a meeting of flu experts, including damage to the alveoli -- the structures in the lung that deliver oxygen to the blood.

This in turn caused what is known as acute respiratory distress syndrome -- an often fatal development that leaves patients gasping for breath.

The World Health Organisation has confirmed 3,205 deaths globally from swine flu but experts agree all estimates of the extent of the pandemic are grossly understated because so few patients are ever actually tested.

Seasonal flu kills, too -- about 250,000 to 500,000 cases a year globally, according to the WHO. But not in the same way as swine flu, which unlike seasonal flu frequently causes severe disease in young adults and children.

"It is very rarely you see what we call diffuse alveolar damage in fatal seasonal influenza," Zaki told a meeting sponsored by the U.S. Institute of Medicine, which advises government on health matters.

Seasonal flu causes bronchitis and other upper respiratory disease. But Zaki, the chief infectious disease pathologist at CDC, said the new virus had burrowed into the lungs of the 90 or so people he examined after they died, and they had huge amounts of the virus in their blood.

"This is almost exactly what we see with avian flu," Zaki said. "This looks like avian flu on steroids."

Dr. Yoshi Kawaoka of the University of Wisconsin said tests in monkeys showed the virus lives and replicates 1,000-fold better in the lungs than does seasonal flu.

He said the No. 1 drug of choice against H1N1 -- Roche's and Gilead Sciences Inc's Tamiflu -- lowered the so-called viral load of virus in the lungs just enough to help the body fight back.

Experimental flu drugs lower it even more, notably Daiichi Sankyo's CS 8958 and another drug called T-705 or favipiravir, made by Fujifilm Holdings unit Toyama Chemical, Kawaoka said.

Zaki said 90 percent of the fatalities he looked at had some condition that would predispose them to serious disease. They had a median age of 38 and one victim was a two-month-old infant who died within a day of getting sick.

Nearly half -- 46 percent -- were obese, many had fatty liver disease, 27 percent had heart disease and 22 percent had asthma, he said.

Dr. Guillermo Ruiz-Palacios of Mexico's National Institute of Medical Sciences and Nutrition said many Mexican patients with severe disease were also obese. In addition, patients came in late for treatment and many were infected with a second common virus, called parainfluenza virus.

Fewer than a third of the U.S. deaths, 29 percent, had a so-called secondary bacterial infection, usually Streptococcus pneumoniae, Zaki said.

Ruiz-Palacios also said the new virus can be found in the urine and faeces of patients, something that may affect how it spreads.

(hat tip pfi/sand)

[indigo girl]

Pandemic flu can infect cells deep in the lungs, says new research

http://www.bio-medicine.org/biology-news-1/Pandemic-flu-can-infect-cells-deep-in-the-lungs--says-new-research-9859-1/

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.

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.