Swine flu facts and fallacies

• What is swine flu?

Swine flu is a respiratory illness caused by a type A influenza virus, usually of the subtype H1N1, that triggers outbreaks in pigs fairly regularly. It can also be transferred from pigs to humans, from humans to pigs, and from humans to other humans.

Four main virus subtypes – H1N1, H1N2, H3N2 and H3N1 – have been isolated in pigs, though the virus, like all influenza viruses, constantly mutates. When influenza viruses from different species infect pigs, the viruses can trade genes to create new versions that mix swine, human and/or avian influenza.

The swine H1N1 virus is not the same as the human H1N1 virus, so vaccines for the latter won't protect from the former.

• Can humans catch swine flu?

Yes, but it is not common. Usually, this happens to people who are in contact with pigs, though there are some documented cases of human-to-human transfer. Human-to-human transmission is believed to occur much like the regular flu, through coughing, sneezing and other contact. Eating pork does not transmit the virus. The symptoms resemble those of the regular flu virus.

• How can swine flu be diagnosed and treated?

Diagnosing requires a respiratory specimen taken during the first four or five days of infection, to be analyzed in a lab. The virus seems to respond to antiviral drugs, including those Canadian health authorities have been stockpiling in case of a flu pandemic.

• When has it happened before?

The best-known case of swine flu is a 1976 outbreak at an army barracks in Fort Dix, N.J., which sickened four soldiers and killed one. There have been no major outbreaks of swine flu recorded in Canada.

• How is swine flu H1N1 virus different from SARS and avian flu H5N1 virus?

All three come from animals, but SARS, a corona virus, and the avian flu are poorly adapted to infecting humans. As a result, it is fairly difficult for humans to catch either virus or pass them on to others, though the effects can prove deadly when infection occurs.

SOURCES: Centers for Disease Control; World Health Organization; Ontario Agency for Health Protection and Promotion

Influenza A virus subtype H1N1

H1N1 is a subtype of the species Influenza A virus. The "H" refers to the Hemagglutinin protein, and the "N" refers to the Neuraminidase protein. H1N1 has mutated into various strains including the Spanish Flu strain (now extinct in the wild), mild human flu strains, endemic pig strains, and various strains found in birds. A variant of H1N1 was responsible for the Spanish flu pandemic that killed some 50 million to 100 million people worldwide from 1918 to 1919. A different variant exists in pig populations.

Low pathogenic H1N1 strains still exist in the wild today, causing roughly half of all flu infections in 2006.^[2] When the 1918 virus was compared with human flu viruses in 2005, it was noticed that it had alterations in just 25 to 30 of the virus's 4,400 amino acids. These changes were enough to turn a bird virus into a version that was human-transmissible.

In April of 2009, an H1N1 outbreak killed over eighty in Mexico, and was believed to have infected more than 1500 individuals worldwide as of April 26, 2009. The U.S. Centers for Disease Control warned that it was possible the outbreak could develop into a pandemic.

From Wikipedia, the free encyclopedia