A better name for the influenza virus causing alarm around the world may be 'North-American influenza' rather than 'swine influenza' the World Organisation for Animal Health (OIE) has suggested. The reason for this proposal is that the virus has not actually been isolated from pigs to date. OIE points out that in the past, many human influenza epidemics with animal origin have been named using their geographic name, eg Spanish influenza or Asiatic influenza, thus it would be logical to call this disease "North-American influenza".
The virus causing fear of a pandemic is a new strain of H1N1 influenza A virus that has components of swine, avian and human viruses. Evidence that the new strain of influenza A virus has entered the human population directly from pigs has not been established, but this is being investigated by FAO. It is also not known if animals are susceptible to this new virus – another urgent area for research.
Looking through the CAB Abstracts database, reports of swine influenza viruses in humans (and also human influenza viruses in pigs), although not common, are not new. Previously, however, most cases have been due to direct contact with pigs and spread has been limited. Interestingly, swine influenza was first recognized in 1918 during the great human influenza pandemic and it is still unknown whether the virus originated in humans, pigs or another species1. What is known is that pigs can be infected with more than one influenza virus at a time and this provides an opportunity for genes from these viruses to mix. A paper published last year in Journal of Infectious Diseases highlighted that 'control of influenza virus infection in poultry and swine is critical to the reduction of potential cross-species adaptation and spread of influenza viruses, which will minimize the risk of animals being the source of the next pandemic2'.
1. Reicks, D. L. (2003) Swine flu (what should we know and how to control in herds). The North American Veterinary Conference Large Animal. Orlando, Florida, USA, 18-22 January, 2003, pp. 333-334
2. Thacker, E. , Janke, B. (2008) Swine influenza virus: zoonotic potential and vaccination strategies for the control of avian and swine influenzas. Journal of Infectious Diseases, Vol. 197, Suppl. 1, pp. S19-S24