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“Swine flu”. Human cases due to H1N1 Influenza virus, an issue that so far only affects Public Health

Joaquín Goyache
April 27th, 2009

Swine Influenza (also known as “swine flu”) is an acute respiratory disease of pigs caused by type A Influenza virus. Its characteristic symptoms are cough, respiratory problems, fever and depression, and although the disease usually has a sudden start animals rapidly recover from the disease. Typically, mortality levels are very low. Swine influenza was first described as an animal disease during the 1918-1919 pandemic known as “Spanish flu”.

The subtypes of the virus that are commonly found worldwide in the swine population are H1N1, H1N2 and H1N3. It is not unusual to find swine strains infecting humans, although it is considered an occupational disease that usually affects people that are in close contact with pigs. However, so far no epidemiological link between pigs and the cases infected with the subtype H1N1 reported in Mexico and USA has been found. In fact, no evidence of contacts between patients and swine has been described. The genetic analysis of the virus isolated in these outbreaks has demonstrated it has fragments described on human Influenza viruses, as well as segments from swine and avian Influenza viruses from North America. In addition it harbors fragments from Eurasian swine viruses. This is a very unusual fact, and actually constitutes the first report of such a quadruple genetic combination in the world.

To date what has been confirmed is the spatial and temporal coincidence between the outbreak in Mexico and the cases in the USA. Anyway, these are very unusual facts, and therefore the implementation of surveillance systems, not only in the affected countries but all over the world, is a rational approach.  Due to the likely person-to-person transmission of this virus, and because of the short space of time required to travel very long distances, the pathogen could be introduced in countries located far away from the affected regions in a few hours. Measures adopted after the emergence of SARS (Severe Acute Respiratory Syndrome)and its fast spread  in November 2002, and of subtype H5N1 of Avian Influenza in 1997, 2003 and the following ones, have allowed the National and International authorities to give a rapid and efficient response. At this moment they only have to adapt these measures to the current needs.

The fact that the food-borne transmission of this virus has not been demonstrated so far must be highlighted, and thus consumption of pork derived food products is still as safe as it has always been. Moreover, if this virus would be transmitted from human to swine, and would spread in our pig population, sanitary control systems already put in place in Spain (and in the European Union) would prevent any contaminated food product derived from an infected animal to enter to the consumption chain. In addition, this virus is extremely sensitive to high temperatures, and thus normal cooking of food products would inactive it.

Therefore, the name “swine flu” given to the outbreak reported in Mexico and in USA these days has been used just because of the history of the evolution of this virus combined with the discovery of elements typically found in swine Influenza viruses isolated from pigs. The fact that the origin of this strain and how it has reached human population is still unknown, added to the lack of evidence of contact between infected patients and swine, demonstrate that, from an epidemiological point of view, this pathogen should be named exclusively as a H1N1 type A Influenza virus, thus removing the term “swine flu”.


Joaquín Goyache

VISAVET Health Surveillance Centre
Complutense University






Article data

Title:
“Swine flu”. Human cases due to H1N1 Influenza virus, an issue that so far only affects Public Health
Author:
Joaquín Goyache
Online publication date:
April 27th, 2009
Keythems:
Innate response, Inmune recognition, Tuberculosis, Mycobacterium bovis

Author data
Joaquín Goyache
VISAVET. Health Surveillance Centre
Complutense University
Madrid (Spain)
Joaquín Goyache BiographyDatos de contactoI+D+i data
More informatión

1 CDC Swine Influenza

2 ECDC

3 WHO Swine Influenza

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