Donal G. McNeil Jr. and Denise Grady, New York Times, 2 January 2011 (hat tip: MR).
The virus that scientists made more contagious was the A(H5N1) avian flu. In its natural form, it is known to have infected only about 600 people since its discovery in 1997, but it killed more than half of them. Humans almost never transmit it to one another. But if that ever were to change, bird flu could become one of history’s worst pandemics…
The new virus does not seem as contagious as either the 1918 Spanish flu or the 2009 swine flu, Dr. Fouchier said. To become airborne, the virus required a range of genetic modifications — “a combination of everything,” he said.
In humans, bird flu viruses live best in the lower lungs, he said, which makes it harder for them to escape in sneezes and coughs. If one could replicate in the upper airways, it would be more likely to be released as an aerosol and might be more transmissible.
If the virus were shed, or expelled, as individual particles instead of in clumps, said Dr. Fouchier, it would be more easily spewed out in the tiny droplets of a cough.
“It also may help if the virus induces coughing or sneezing,” Dr. Fouchier added.
Modifications to any of these viral traits may help make the bird flu virus more contagious. And in fact, it took only a few mutations to make the new virus, he said.
Dr. Fouchier declined to describe them in detail.
As Tyler Cowen notes the anomalies don’t appear all that anomalous. In fact the whole article seems to be a bit too cheerful. It ends with the following comment:
There is one reassuring note in the unsettling findings from Rotterdam and Wisconsin. Fearsome though it may be, the new virus appears to be vulnerable to existing vaccines and flu drugs.
Given that neither have done much to stop large (non-lethal) epidemics, I am not sure I find that last point very comforting. It is a little like saying, "Look on the bright side! It will give the Apocalyptic Iranian's something to do besides work on nuclear bombs."