Outbreaks in humans - 1976 U.S. outbreak
On February 5, 1976, an army recruit at 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 swine flu was the cause of death and that this strain of flu appeared to be closely related to the strain involved in the 1918 flu pandemic. Alarmed public-health officials decided that action must be taken to head off another major pandemic, and they urged President Gerald Ford that every person in the U.S. be vaccinated for the disease.
However, the vaccination program was plagued by delays and public relations problems. But on Oct. 1, 1976, the immunization program began and by Oct. 11, approximately 40 million people, or about 24% of the population, had received swine flu immunizations. That same day, three senior citizens died soon after receiving their swine flu shots and there was a media outcry linking the deaths to the immunizations, despite not having any positive proof. According to science writer Patrick Di Justo, however, by the time the truth was known — that the deaths were not proven to be related to the vaccine — it was too late. "The government had long feared mass panic about swine flu — now they feared mass panic about the swine flu vaccinations." This became a strong setback to the program.
There were 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 influenza vaccines, with an incidence of about one case per million vaccinations. As a result, Di Justo writes that "the public refused to trust a government-operated health program that killed old people and crippled young people." In total, less than 33 percent of the population had been immunized by the end of 1976. The National Influenza Immunization Program was effectively halted on Dec. 16.
Overall, about 500 cases of Guillain-Barré syndrome (GBS), resulting in death from severe pulmonary complications for 25 people, which, according to Dr. P. Haber, were probably caused by an immunopathological reaction to the 1976 vaccine. Other influenza vaccines have not been linked to GBS, though caution is advised for certain individuals, particularly those with a history of GBS. Still, as observed by a participant in the immunization program, the vaccine killed more Americans than the disease did.
Outbreaks in humans - 1988 swine flu outbreak
In September 1988, a swine flu virus killed one woman in Wisconsin, and infected at least hundreds of others. 32-year old Barbara Ann Wieners was eight months pregnant when she and her husband, Ed, became ill after visiting the hog barn at the Walworth County Fair. Barbara died eight days later, though doctors were able to induce labor and deliver a healthy daughter before she passed away. Her husband recovered from his symptoms.
Influenza-like illnesses were reportedly widespread among the pigs at the fair they had visited, and 76% of the swine exhibitors there tested positive for the swine flu antibody but no serious illnesses were detected among this group. Additional studies suggested between one and three health care personnel who had contact with the patient developed mild influenza-like illnesses with antibody evidence of swine flu infection.
Outbreaks in humans - 2009 swine flu outbreak
The new strain of swine influenza A (H1N1) involved in the 2009 flu outbreak in humans is a reassortment of several strains of influenza A virus subtype H1N1 that are, separately, endemic in humans, endemic in birds, and endemic in swine. Preliminary genetic characterization found that the hemagglutinin (HA) gene was similar to that of swine flu viruses present in United States pigs since 1999, but the neuraminidase (NA) and matrix protein (M) genes resembled versions present in European swine flu isolates. Viruses with this genetic makeup had not previously been found to be circulating in humans or pigs, but there is no formal national surveillance system to determine what viruses are circulating in pigs in the United States. The origins of this new strain remain unknown.
The earliest known human case, 5 year old Edgar Hernandez, was near a pig farm in La Gloria, Veracruz state, Mexico, that raises almost 1 million pigs a year. Residents of La Gloria have long complained about the clouds of flies that are drawn to the so-called 'manure lagoons' created by such mega-farms. Edgar Hernandez was thought to be suffering from ordinary influenza but laboratory testing revealed he had contracted swine flu. The boy went on to make a full recovery.
"If the people who are supposed to be familiar with this didn't know what it was, how will we ever know how my son got it?" Edgar's mother, Hernandez said.
La Gloria, Perote, Veracruz is a small community, surrounded by large pig farms. Reports indicate that during February 2009 over 400 persons in the town had flu like symptoms and 2 infants died of 'pneumonia'.
Juan Rodriguez died of 'pneumonia' February 9th at age 7 months.
Yovanni Apolinar died of 'pneumonia' March 12th at age 2 months.
Unidentified mexican toddler contracted swine flu in Brownsville, Texas, United States and died of swine flu April 29th in Houston, Texas, United States at age 23 months.
The United States Department of Agriculture researchers say that while pig vaccination keeps pigs from getting sick, it does not block infection or shedding of the virus.
Dr. Anne Schuchat, interim Deputy Director for CDC Science and Public Health, said that the American cases were found to be made up of genetic elements from four different flu viruses – North American swine influenza, North American avian influenza, human influenza, and swine influenza virus typically found in Asia and Europe – "an unusually mongrelised mix of genetic sequences." Pigs have been shown to act as a potential "mixing vessel" in which reassortment can occur between flu viruses of several species. This new strain appears to be a result of reassortment of human influenza and swine influenza viruses, presumably due to superinfection in an individual human. Influenza viruses readily undergo reassortment due to antigenic shift because their genome is split between eight pieces of RNA (see Orthomyxoviridae).
The current strain of swine flu can adapt to humans and spread more efficiently than previously known swine H1N1 strains. Moreover, co-infection of H1N1 swine flu and Oseltamivir resistant H1N1 season flu can lead to acquisition of the H274Y mutation by the swine flu via recombination or reassortment. Swine H1N1 with human H1 and N1 have been reported.
The 1918 flu pandemic strain had undergone polymorphism from swine and human H1N1 in all eight pieces of RNA gene segments. Similar swapping of gene segments in humans co-infected with seasonal human influenza and swine H1N1 can lead to rapid evolution.
The new strain of swine influenza A (H1N1) is currently listed by the United States and World Health Organization as a Stage 5 pandemic virus
Source: Swine Influenza Top News
Showing posts with label The H1N1. Show all posts
Showing posts with label The H1N1. Show all posts
The H1N1 Background (Swine influenza)
The H1N1 form of swine flu is one of the descendants of the Spanish flu that caused a devastating pandemic in humans in 1918–1919. 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 12 cases in the U.S. since 2005.
The flu virus is perhaps the trickiest known to medical science; it constantly changes form to elude the protective antibodies that the body has developed in response to previous exposures to influenza or to influenza vaccines. Every two or three years the virus undergoes minor changes. Then, at intervals of roughly a decade, after the bulk of the world's population has developed some level of resistance to these minor changes, it undergoes a major shift that enables it to tear off on yet another pandemic sweep around the world, infecting hundreds of millions of people who suddenly find their antibody defenses outflanked. Even during the Spanish flu pandemic, the initial wave of the disease was relatively mild, while the second wave was highly lethal.
In 1957, an Asian flu pandemic infected some 45 million Americans and killed 70,000. Eleven years later, lasting from 1968 to 1969, the Hong Kong flu pandemic afflicted 50 million Americans and caused 33,000 deaths, costing approximately $3.9 billion. In 1976, about 500 soldiers became infected with swine flu over a period of a few weeks. However, by the end of the month investigators found that the virus had "mysteriously disappeared", and there were no more signs of swine flu anywhere on the post. There were isolated cases around the U.S., but those cases were supposedly to individuals who caught the virus from pigs.
Medical researchers worldwide, recognizing that the swine flu virus might again mutate into something as deadly as the Spanish flu, were carefully watching the latest 2009 outbreak of swine flu and making contingency plans for a possible global pandemic.
Swine influenza Classification
SIV strains isolated to date have been classified either as Influenzavirus C or one of the various subtypes of the genus Influenzavirus A.
Influenza A, Swine influenza is known to be caused by influenza A subtypes H1N1, H1N2, H3N1, H3N2, and H2N3.
In swine, three influenza A virus subtypes (H1N1, H3N2, and H1N2) are circulating throughout the world. In the United States, the H1N1 subtype was exclusively prevalent among swine populations before 1998; however, since late August 1998, H3N2 subtypes have been isolated from pigs. As of 2004, H3N2 virus isolates in US swine and turkey stocks were triple reassortants, containing genes from human (HA, NA, and PB1), swine (NS, NP, and M), and avian (PB2 and PA) lineages.
Source: Swine Influenza Top News
The flu virus is perhaps the trickiest known to medical science; it constantly changes form to elude the protective antibodies that the body has developed in response to previous exposures to influenza or to influenza vaccines. Every two or three years the virus undergoes minor changes. Then, at intervals of roughly a decade, after the bulk of the world's population has developed some level of resistance to these minor changes, it undergoes a major shift that enables it to tear off on yet another pandemic sweep around the world, infecting hundreds of millions of people who suddenly find their antibody defenses outflanked. Even during the Spanish flu pandemic, the initial wave of the disease was relatively mild, while the second wave was highly lethal.
In 1957, an Asian flu pandemic infected some 45 million Americans and killed 70,000. Eleven years later, lasting from 1968 to 1969, the Hong Kong flu pandemic afflicted 50 million Americans and caused 33,000 deaths, costing approximately $3.9 billion. In 1976, about 500 soldiers became infected with swine flu over a period of a few weeks. However, by the end of the month investigators found that the virus had "mysteriously disappeared", and there were no more signs of swine flu anywhere on the post. There were isolated cases around the U.S., but those cases were supposedly to individuals who caught the virus from pigs.
Medical researchers worldwide, recognizing that the swine flu virus might again mutate into something as deadly as the Spanish flu, were carefully watching the latest 2009 outbreak of swine flu and making contingency plans for a possible global pandemic.
Swine influenza Classification
SIV strains isolated to date have been classified either as Influenzavirus C or one of the various subtypes of the genus Influenzavirus A.
Influenza A, Swine influenza is known to be caused by influenza A subtypes H1N1, H1N2, H3N1, H3N2, and H2N3.
In swine, three influenza A virus subtypes (H1N1, H3N2, and H1N2) are circulating throughout the world. In the United States, the H1N1 subtype was exclusively prevalent among swine populations before 1998; however, since late August 1998, H3N2 subtypes have been isolated from pigs. As of 2004, H3N2 virus isolates in US swine and turkey stocks were triple reassortants, containing genes from human (HA, NA, and PB1), swine (NS, NP, and M), and avian (PB2 and PA) lineages.
Source: Swine Influenza Top News
Subscribe to:
Posts (Atom)
Posts
