Posts Tagged ‘Centers for Disease Control’

Swine Flu Update

Cliff Notes for “Swine flu: One Killer virus, three key questions.”

swine flu virusBy Ilene

Brendan Maher and Declan Butler, authors of a recently published Nature article “Swine flu: One killer virus, three key questions,” set out to answer three questions about the H1N1 virus. Here’s what they found. 

How does it kill?

Sherif Zaki, head of the infectious-disease pathology branch at the Centers for Disease Control, discusses his team’s observations from their pathological studies.    

1.  The H1N1 virus penetrates deep into the alveoli (the terminal air sacs in the lungs). In contrast, the seasonal flu viruses tend to infect cells higher in the upper airways. This deep penetration is reminiscent of the action of the H5N1 avian flu virus. Zaki commented: “[H1N1] is like avian flu on steroids.”  Why might this be?

Zaki says that his observations fit well with recent research looking at the mechanism of infection. A group led by Mikhail Matrosovich at Philipps University Marburg in Germany and Ten Feizi at Imperial College London studied sialyl glycans, glycoproteins that the flu virus binds to in order to gain entry to human cells. Although seasonal strains of H1N1 bind mostly to versions of the glycoproteins known as α2-6, the researchers found that the new pandemic H1N1 can also bind to a version called α2-3, which is found in greater proportion in the lower respiratory tract.

2.  In patients who have died, co-infection was common with H1N1.  Zaki’s group observed infection with bacteria such as Staph aureus or Streptococcus pneumoniae in about a third of the fatal swine-flu cases. However, in the remaining two thirds of fatal cases, the virus was lethal alone.  The damage seen in the lungs is characterized as ‘diffuse alveolar damage,’ reflecting a very difficult to treat state of respiratory distress syndrome. According to Zaki’s research, about 90% of the fatal cases had some underlying medical condition.

Zaki expects the number of flu cases to increase as the flu season “ramps up.”

How does H1N1 spread?

Brendan Maher visited Peter Palese’s laboratory at Mount Sinai School of Medicine where testing for how the viruses spread is being carried out. Researchers John Steel and Anice Lowen compared the transmissibility of H1N1 to that of seasonal flu using a guinea pig model. Their data indicate that the H1N1 virus transmits as efficiently as seasonal flu viruses, which is consistent with real-world data showing…
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