Friday, 8 May, 2009

Swine Flu - There's been an outbreak before..

1918 Flu Pandemic

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.

For the following 60 years,swine influenza strains -- H1N1

1997-2002 -- new strains evolved of 3 different Subtypes and 5 different Genotypes

1997-1998 -- H3N2 -- include genes derived by reassortment from human, swine and avian viruses-North America

H1N1 -- Reassortment between H1N1 and H3N2-North America

1999 -- H4N6 -- crossed the species barrier from birds to pigs -contained on a single farm in Canada

The H1N1 form of swine flu is one of the descendants of the strain that caused the 1918 flu pandemic.As well as persisting in pigs,the descendants of the 1918 virus have also circulated in humans through the 20th century, contributing to the normal seasonal epidemics of influenza.However, direct transmission from pigs to humans is rare, with only 12 cases in the U.S. since 2005.

Till today though the exact origin of the 1918 strain remains elusive..
1976 U.S. outbreak

February 5, 1976 -- A/New Jersey/1976 (H1N1)- a U.S army recruit Fort Dix said he felt tired and weak. He died the next day and four of his fellow soldiers were later hospitalized. Two weeks after his death, health officials announced that the cause of death was a new strain of swine flu. The strain, a variant of H1N1, is known as A/New Jersey/1976 (H1N1). It was detected only from January 19 to February 9 and did not spread beyond Fort Dix.

-- A/Victoria/75 (H3N2)-ensuing increased surveillance uncovered another strain in circulation in U.S.

Alarmed public-health officials decided action must be taken to head off another major pandemic, and urged President Gerald Ford that every person in the U.S. be vaccinated for the disease.

About 24% of the population, had received immunizations when three senior citizens died soon after receiving their swine flu shots and there was a media outcry linking the deaths to the immunizations, despite the lack of positive proof. There were also reports of Guillain-Barré syndrome,a paralyzing neuromuscular disorder, affecting some people who had received swine flu immunizations. This syndrome is a rare side-effect of modern influenza vaccines, with an incidence of about one case per million vaccinations.Less than 33% of the population had been immunized by the end of 1976. The National Influenza Immunization Program was effectively halted on Dec. 16.Overall, there were about 500 cases of Guillain-Barré syndrome (GBS), resulting in death from severe pulmonary complications for 25 people,the vaccine killed more Americans than the disease did.

1988 zoonosis

In September 1988, a swine flu virus killed one woman in Wisconsin, and infected at least hundreds of others.
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. This outbreak confirmed that pigs can serve as a crucible where novel influenza viruses emerge as a result of the reassortment of genes from different strains.
Swine Flu - It spreads outside the US

2007 Philippine outbreak in swine

On August 20, 2007 Department of Agriculture officers investigated the outbreak (epizootic) of swine flu in Nueva Ecija and Central Luzon, Philippines.

2009 - Swine Flu

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