Important facts about swine flu
What is swine flu?
Swine influenza (also called H1N1 flu, swine flu, hog flu, and pig flu) is an infection by any one of several types of swine influenza virus. Swine influenza virus is common throughout pig populations worldwide. Swine influenza virus (SIV) is any strain of the influenza family of viruses.
How many types of flu viruses are there?
Of the three genera of influenza viruses that cause human flu, two also cause influenza in pigs, with influenza A being common in pigs and influenza C being rare. Influenza B has not been reported in pigs. Swine influenza is known to be caused by influenza A subtypes H1N1, H1N2, H3N1, H3N2 and H2N3. In pigs, three influenza A virus subtypes (H1N1, H3N2, and H1N2) are the most common strains worldwide
Swine influenza was first proposed to be a disease related to human influenza during the 1918 flu pandemic, when pigs became sick at the same time as humans. The first identification of an influenza virus as a cause of disease in pigs occurred about ten years later, in 1930.
1918 pandemic in humans
The 1918 flu pandemic in humans was associated with H1N1 and influenza appearing in pigs; this may reflect a zoonosis either from swine to humans, or from humans to swine. Although it is not certain in which direction the virus was transferred, some evidence suggests that, in this case, pigs caught the disease from humans.
1976 U.S. outbreak
This new strain appeared to be closely related to the strain involved in the 1918 flu pandemic. Moreover, the ensuing increased surveillance uncovered another strain in circulation in the U.S.: A/Victoria/75 (H3N2) spread simultaneously, also caused illness, and persisted until March. On October 1, 1976, the immunization program began and by October 11, approximately 40 million people, or about 24% of the population, had received swine flu immunizations.
In September 1988, a swine flu virus killed one woman and infected others. Influenza-like illness (ILI) was reportedly widespread among the pigs However, there was no community outbreak.
1998 US outbreak in swine
In 1998, swine flu was found in pigs in four U.S. states. Within a year, it had spread through pig populations across the United States. Scientists found that this virus had originated in pigs as a recombinant form of flu strains from birds and humans.
2007 Philippine outbreak in swine
On August 20, 2007 Department of Agriculture officers investigated the outbreak of swine flu in Philippines. The mortality rate is less than 10% for swine flu, unless there are complications like hog cholera.
2009 outbreak in humans
The H1N1 viral strain implicated in the 2009 flu pandemic among humans often is called “swine flu” because initial testing showed many of the genes in the virus were similar to influenza viruses. But further research has shown that the outbreak is due to a new strain of H1N1 not previously reported in pigs.
Transmission of the virus from pigs to humans is not common and does not always lead to human influenza. If transmission does cause human influenza, it is called zoonotic swine flu. People with regular exposure to pigs are at increased risk of swine flu infection. People who work with poultry and swine, especially people with intense exposures, are at increased risk of zoonotic infection with influenza virus endemic in these animals, and constitute a population of human hosts in which zoonosis and reassortment can co-occur. Vaccination of these workers against influenza and surveillance for new influenza strains among this population may therefore be an important public health measure. Other professions at particular risk of infection are veterinarians and meat processing workers, although the risk of infection for both of these groups is lower than that of farm workers
Signs & Symptoms
Symptoms of zoonotic swine flu in humans are similar to those of influenza and of influenza-like illness in general, namely chills, fever, sore throat, muscle pains, severe headache, coughing, weakness and general discomfort. The strains of swine flu rarely pass from human to human. The 2009 H1N1 virus is not zoonotic swine flu, as it is not transmitted from pigs to humans, but from person to person.
The most common cause of death is respiratory failure, other causes of death are pneumonia (leading to sepsis); high fever (leading to neurological problems), dehydration (from excessive vomiting and diarrhea) and electrolyte imbalance. Fatalities are more likely in young children and the elderly.
Prevention of human to human transmission
Influenza spreads between humans through coughing or sneezing and people touching something with the virus on it and then touching their own nose or mouth Swine flu cannot be spread by pork products, since the virus is not transmitted through food. The swine flu in humans is most contagious during the first five days of the illness although some people, most commonly children, can remain contagious for up to ten days
Recommendations to prevent spread of the virus among humans include using standard infection control against influenza. This includes frequent washing of hands with soap and water or with alcohol-based hand sanitizers, especially after being out in public. Chance of transmission is also reduced by disinfecting household surfaces, which can be done effectively with a diluted chlorine bleach solution
Social distancing is another tactic. It means staying away from other people who might be infected and can include avoiding large gatherings
Vaccines are available for different kinds of Swine Flu.
The blue surgical masks you’ve seen being passed out to Mexican pedestrians are better than nothing but probably only marginally useful, said Andrew Pekosz, associate professor of microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland.
While such masks block the relatively large, virus-carrying droplets sneezed out by infected people, the viruses themselves are much smaller and could easily pass through. Specialty masks, designated N-95 or N-99, are better filters but still not perfect.
For better protection, Pekosz recommends combining a mask with regular hand washing and keeping 3 to 4 feet (90 to 120 centimeters) away from other people
The WHO’s pandemic alert level has been raised a notch to level 4. Level 5 is considered a pandemic – with “sustained community-level transmission” in at least two countries – and level 6 a full-scale global pandemic affecting more than one region in the world.