[Updates have been added to this post (see end) - note particularly the 11th May update suggesting that "swine-origin" is justified.]
The new strain of the H1N1 influenza virus that has emerged in Mexico, with particular virulence, and is now spreading to other parts of the globe is almost universally reported as swine flu. The name suggests a clear and direct link with pigs, but is it really that simple?
What’s the connection with pigs?
ProMED explains that the term “swine flu” refers to the history and evolution of H1N1 viruses in general. (Thanks to the always excellent and sober Warmwell, a first point of reference for any question of livestock disease, for pointing me to this source)
Although H1N1 may have first originated in birds, earlier strains have circulated and resulted in mortality in pig and human populations, with frequent transmission demonstrated from pigs to humans.
In the particular case of the current, new strain of H1N1, New Scientist reports that the genetic make-up is a combination of pig, bird and human flu viruses.
A more accurate name: Influenza A (H1N1) virus, human
ProMED prefers the description “Influenza A (H1N1) virus, human”, fearing that “swine flu” is infelicitous, because:
there really does appear to be no exposure to swine and some evidence (father, daughter pair in the US) of transmission without exposure to animals
and, worse, dangerously misleading, because it:
will imply a simple, zoonotic transmission between swine and people, when in reality is origin and epidemiology is likely to be much more complex
(ProMED update, 26th April 2009)
The key unanswered question is when and where the new strain emerged and was first transmitted to a human patient. At least until some new epidemiological evidence comes to light, the strain appears to be more a human flu than a swine flu.
The FAO has issued a press release stating that it is mobilising experts to ascertain whether there is any direct connection between the new strain of H1N1 and pigs. There is currently no evidence of the virus circulating in pigs or having been transmitted from pigs to humans. It is not even clear whether the new strain could infect a pig. The FAO chief veterinary officer explained: There is no evidence of a threat to the food chain; at this stage it is a human crisis and not an animal crisis, but we have to be alerted and prepared. The first actions FAO and others must take are to ascertain if the new strain is circulating in pigs, establish if there are any direct linkages between the illness in the human population and animals and explain how this new virus has obtained genetic materials from human, bird and pig influenza strains.
Update (later on 28th April) – FAO mobilising experts to ascertain whether any link to pigs
Moves to drop the name “swine flu” have been widely criticised as motivated purely by the interests of pork producers. It’s undeniable that pork producers don’t like the “swine flu” name but this doesn’t, in itself, counter the arguments for an alternative name. As the origins of the novel H1N1 strain become better understood, it’s increasingly clear that the virus is actually of relatively recent swine origin, the reassortment of swine, avian and human viruses having most likely occurred some time ago in pigs. Furthermore, there’s some scientific consensus that the nature of pigs and modern pig production played an important role in the development of this novel strain (and others). The link with swine is important. Although the exact source is yet to be identified, it seems reasonable to call the virus “swine-origin”: in full “novel swine-origin influenza A (H1N1) virus, human“.
Further update (11th May)
