There appears to be uncertainty over just which genes are in the H1N1 genome now causing illness.
(Update: Must read for anyone interested in the present situation: the CIDRAP Swine Influenza Overview.)
As of the evening of Tuesday, 28 April, CNN is reporting that:
The new virus has genes from North American swine influenza, avian influenza, human influenza and a form of swine influenza normally found in Asia and Europe, said Nancy Cox, chief of the CDC's Influenza Division.
However, today's ProMED mail contained a the following exchange.
From Professor Roger Morris, at Massey University, New Zealand, a whole bunch of really good questions:
For those of us who are involved in international work on influenza epidemiology and control and responding to the many media enquiries, there is a very large information gap in relation to diagnosis and epidemiology of the Mexican influenza. What is known of the genetic structure of this virus? It has been called a swine flu, but no evidence has been put forward to allow this statement to be evaluated. I have received information that it is a reassortant, which has genetic components from 4 different sources, but nothing official has been released on this. Where does it fit phylogenetically? Is there any genetic variation of significance among the isolates investigated? Would this help to explain the difference in severity of disease between Mexico and other countries?
It is also stated that it should be diagnosed by RT-PCR, without clarifying which PCR. I have received information that the standard PCR for H1 does not reliably detect this virus. Is this true? What is an appropriate series of diagnostic steps for samples from suspect cases? Could we have an authoritative statement on these issues from one of the laboratories, which has been working with the virus?
In response, here is Professor Paul Rabadan, of Columbia University College of Physicians and Surgeons, who is digging into the flu genome sequences filed at NCBI and finds that the sequence appears to be solely of swine (swinian?) origin:
In relation to the questions posed by Prof. Morris: My group and I are analyzing the recent sequences from the isolates in Texas and California of swine H1N1 deposited in National Center for Biotechnology Information (NCBI) (A/California/ 04/2009(H1N1), A/California/05/2009(H1N1), A/California/ 06/2009(H1N1), A/California/07/2009(H1N1), A/California/09/2009(H1N1), A/Texas/04/2009(H1N1) and A/Texas/05/2009(H1N1).
The preliminary analysis using all the sequences in public databases (NCBI) suggests that all segments are of swine origin. NA and MP seem related to Asian/European swine and the rest to North American swine (H1N2 and H3N2 swine viruses isolated since 1998). There is also interesting substratification between these groups, suggesting a multiple reassortment.
We are puzzled about sources of information that affirm that the virus is a reassortment of avian, human and swine viruses. It is true that the H3N2 swine virus from 1998 and 1999 is a triple reassortant, but all the related isolates are found since then in swine.
In lay English: the virus is composed of pieces of other viruses found in pigs. While the structure of the genome is curious, in that it appears the different viruses exchanged chromosomes multiple times, there isn't any sign that the present genome of concern contains elements of avian or human flu viruses.
(Update: I just stumbled over a 21 April CDC briefing that describes the genomes of H1N1 viruses in pediatric cases in California as entirely of swine origin.)
So it isn't at all clear why the press (and government officials) keep repeating the assertion that the new virus is some sort of amazing Frankenstein strain. The message containing Professor Rabadan's comments also notes that a mess of new sequences from clinical isolates were filed today in the GISAID database. Analysis of those sequences should help clarify the origin -- or at least the composition of the genome -- of the virus in the coming days.
The press also continues to bray about flies as the vector, when there is no evidence I can find in any literature, anywhere, that suggests flies have ever been associated with transmitting the flu. If this particular bug did figure out how to hitch a ride of flies, that would be some seriously scary evolutionary juju. Intelligent design, even. We would all be in deep trouble. But, as there is no evidence to support these assertions other than repeating what other reporters are saying, my recommendation to all you in the press would be simply this: STOP.
Similarly, the notion that at this early date anyone could possibly have identified the index case ("Patient 0") as a young boy in some village in Mexico is -- let me choose my words very carefully here -- COMPLETE PIGSHIT. With so little molecular forensics done on the virus, and no real map of who is actually sick, who has been sick, nor when or where they were sick, publishing the name of an innocent four-year old boy based on cribbing from some other reporter's story is the height of irresponsible journalism. Where the fuck are the editors?
(Update: The New York Times is still repeating this nonesense: "...The Mexican government has identified a young boy as the first person in the country infected with swine flu...". Waaay down in the story it acknowledges that the village the boy is from "may not, in the end, be found to be the source of anything" and then goes on to describe earlier potential cases. Oy.)
Perhaps reporters should try a little, oh, I don't know, reporting. Visit ProMED mail. Check out CIDRAP and Effect Measure. Stop reading what other reporters write, and think for yourseves. We will all be better off.