Swine influenza

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Swine influenza
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 Swine influenza

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El Helalya
المؤسسة

المؤسسة
El Helalya


المشاركات :
22515


تاريخ التسجيل :
08/08/2008


الجنس :
انثى

البلد :
مصر

sms :
سبحان الله

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Swine influenza  _
مُساهمةموضوع: Swine influenza    Swine influenza  Emptyالخميس 10 نوفمبر 2011 - 4:47 




Swine influenza


Swine influenza  800px-Sow_with_piglet

Swine influenza (also swine flu) refers to influenza caused by any strain of the influenza virus endemic in pigs (swine). Strains endemic in swine are called swine influenza virus (SIV). Swine flu is common in swine and rare in humans.
SIV
can mutate into a form that allows it to pass from human to human. The
strain responsible for the 2009 swine flu outbreak is believed to have
undergone such a mutation.[1] People who work with poultry
and swine, especially people with intense exposures, are at risk of
infection with influenza from these animals if the animals carry a
strain that is also able to infect humans. However, these strains rarely
are transmitted from human to human.
In humans, the symptoms of
swine flu 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 strain
responsible for the 2009 swine flu outbreak in most cases causes only
mild symptoms and the infected person recovers fully.
Of the three genera of human flu, two are endemic also in swine: Influenzavirus A (common) and Influenzavirus C (rare).[2]
Influenzavirus B has not been reported in swine. Within Influenzavirus A
and Influenzavirus C, the strains endemic to swine and humans are
largely distinct


Background

The swine flu is a descendant of the infamous "Spanish flu" that caused a devastating pandemic in humans in 1918-1919.[3]
In less than a year, that pandemic killed more than 500,000 Americans
and some 20 million people worldwide - the greatest number ever killed
in so short a period by any natural or man-made catastrophe. It also
killed and sickened large numbers of hogs. Within a decade, the disease
stopped circulating among humans, but it has infected swine ever since.
Although hogs had initially caught the virus from humans, it has
undergone slight changes over the years, emerging occasionally to infect
individuals who work closely with pigs. However, there have only been
12 cases in the U.S. since 2005 in which humans caught swine flu after
being in contact with pigs and there is currently no requirement that
pigs be vaccinated against swine flu. [4]
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.[5]
Even during the Spanish flu pandemic, the initial wave of the disease
was relatively mild and the second wave was highly lethal.[3]
In
1957 there was an Asian flu pandemic that infected some 45 million
Americans and killed 70,000 of them. Eleven years later, lasting from
1968 to 1969, the Hong Kong 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 the
virus had "mysteriously disappeared" and there were no more signs of
swine flu anywhere on the post. [3] There were isolated cases around the U.S. but those cases were supposedly to individuals who caught the virus from pigs.
Medical
researchers worldwide remain vigilant knowing that the swine flu virus
might again mutate into something as deadly as the Spanish flu. They are
carefully watching the latest 2009 outbreak of swine flu and making
contingency plans for a possible global pandemic



Classification
SIV
strains isolated to date have been classified either as Influenzavirus C
or one of the various subtypes of the genus Influenzavirus A.[6]


Influenza A
Swine influenza is known to be caused by influenza A subtypes H1N1,[7] H1N2,[7] H3N1,[8] H3N2,[7] and H2N3.[9]
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.[10]


Interaction with H5N1

Avian
influenza virus H3N2 is endemic in pigs in China and has been detected
in pigs in Vietnam, increasing fears of the emergence of new variant
strains.[11] Health experts[who?] say pigs
can carry human influenza viruses, which can combine (i.e. exchange
homologous genome sub-units by genetic reassortment) with H5N1, passing
genes and mutating into a form which can pass easily among humans.[12] H3N2 evolved from H2N2 by antigenic shift.[13] In August 2004, researchers in China found H5N1 in pigs.[14]
Nature
magazine reported that Chairul Nidom, a virologist at Airlangga
University's tropical disease center in Surabaya, East Java, conducted
an independent research study in 2005. He tested the blood of 10
apparently healthy pigs housed near poultry farms in West Java where
avian flu had broken out. Five of the pig samples contained the H5N1
virus. The Indonesian government has since found similar results in the
same region. Additional tests of 150 pigs outside the area were
negative.[15][16]


Signs and symptoms

Main symptoms of swine flu in humans.[17]


According
to the Centers for Disease Control and Prevention (CDC), in humans the
symptoms of swine flu are similar to those of influenza and of
influenza-like illness in general. Symptoms include fever, cough, sore
throat, body aches, headache, chills and fatigue. The 2009 outbreak has
shown an increased percentage of patients reporting diarrhea and
vomiting.[18]
Because these symptoms are not specific to swine flu, a differential diagnosis of probable
swine flu requires not only symptoms but also a high likelihood of
swine flu due to the person's recent history. For example, during the
2009 swine flu outbreak in the United States, CDC advised physicians to
"consider swine influenza infection in the differential diagnosis of
patients with acute febrile respiratory illness who have either been in
contact with persons with confirmed swine flu, or who were in one of the
five U.S. states that have reported swine flu cases or in Mexico during
the 7 days preceding their illness onset."[19] A diagnosis of confirmed swine flu requires laboratory testing of a respiratory sample (a simple nose and throat swab).[19]

Pathophysiology
Influenza
viruses bind through hemagglutinin onto sialic acid sugars on the
surfaces of epithelial cells; typically in the nose, throat and lungs of
mammals and intestines of birds (Stage 1 in infection figure).[20]


Swine flu in humans

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.[21]
Transmission of influenza from swine to humans who work with swine was
documented in a small surveillance study performed in 2004 at the
University of Iowa.[22] This study among others forms the
basis of a recommendation that people whose jobs involve handling
poultry and swine be the focus of increased public health surveillance.[21]
The 2009 swine flu outbreak is an apparent reassortment of several
strains of influenza A virus subtype H1N1, including a strain endemic in
humans and two strains endemic in pigs, as well as an avian influenza.[23]
The
CDC reports that the symptoms and transmission of the swine flu from
human to human is much like that of seasonal flu. Common symptoms
include fever, lethargy, lack of appetite and coughing, while runny
nose, sore throat, nausea, vomiting and diarrhea have also been
reported.[24] It is believed to be spread between humans
through coughing or sneezing of infected people and touching something
with the virus on it and then touching their own nose or mouth.[25] Swine flu cannot be spread by pork products, since the virus is not transmitted through food.[25]
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. Diagnosis can be made by sending a
specimen, collected during the first five days, to the CDC for analysis.[26]
The
swine flu is susceptible to four drugs licensed in the United States,
amantadine, rimantadine, oseltamivir and zanamivir; however, for the
2009 outbreak it is recommended it be treated under medical advice only
with oseltamivir and zanamivir to avoid drug resistance.[27]
The vaccine for the human seasonal H1N1 flu does not protect against the
swine H1N1 flu, even if the virus strains are the same specific
variety, as they are antigenically very different.[28]
 الموضوع : Swine influenza   المصدر :منتديات تقى الإسلامية  الكاتب:  El Helalya

 توقيع العضو/ه:El Helalya

الرجوع الى أعلى الصفحة اذهب الى الأسفل

El Helalya
المؤسسة

المؤسسة
El Helalya


المشاركات :
22515


تاريخ التسجيل :
08/08/2008


الجنس :
انثى

البلد :
مصر

sms :
سبحان الله

ـــــــــــ


ــــــــــــــ


Swine influenza  _
مُساهمةموضوع: رد: Swine influenza    Swine influenza  Emptyالخميس 10 نوفمبر 2011 - 4:47 

Prevention

Prevention
of swine influenza has three components: prevention in swine,
prevention of transmission to humans, and prevention of its spread among
humans.


Prevention in swine

Swine
influenza has become a greater problem in recent decades as the
evolution of the virus has resulted in inconsistent responses to
traditional vaccines. Standard commercial swine flu vaccines are
effective in controlling the infection when the virus strains match
enough to have significant cross-protection, and custom (autogenous)
vaccines made from the specific viruses isolated are created and used in
the more difficult cases.[29][30]
Present
vaccination strategies for SIV control and prevention in swine farms,
typically include the use of one of several bivalent SIV vaccines
commercially available in the United States. Of the 97 recent H3N2
isolates examined, only 41 isolates had strong serologic cross-reactions
with antiserum to three commercial SIV vaccines. Since the protective
ability of influenza vaccines depends primarily on the closeness of the
match between the vaccine virus and the epidemic virus, the presence of
nonreactive H3N2 SIV variants suggests that current commercial vaccines
might not effectively protect pigs from infection with a majority of
H3N2 viruses.[31][32]

Prevention of transmission to humans

This section requires expansion.

Prevention of spread in humans
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.[33] Vaccines against the H1N1 strain in the 2009 human outbreak are being developed and could be ready as early as June 2009.[34]
Experts
agree that hand-washing can help prevent viral infections, a
surprisingly effective way to prevent all sorts of diseases, including
ordinary influenza and the new swine flu virus. Influenza can spread in
coughs or sneezes, but an increasing body of evidence shows little
particles of virus can linger on tabletops, telephones and other
surfaces and be transferred via the fingers to the mouth, nose or eyes.
Alcohol-based gel or foam hand sanitizers work well to destroy viruses
and bacteria. Anyone with flu-like symptoms such as a sudden fever,
cough or muscle aches should stay away from work or public
transportation and should see a doctor to be tested.
Social
distancing is another tactic. It means staying away from other people
who might be infected and can include avoiding large gatherings,
spreading out a little at work, or perhaps staying home and lying low if
an infection is spreading in a community.

Treatment

The
CDC recommends the use of Tamiflu (oseltamivir) or Relenza (zanamivir)
for the treatment and/or prevention of infection with swine influenza
viruses. The virus isolates that have been tested from the US and Mexico
are however resistant to amantadine and rimantadine.[35] If a
person gets sick, antiviral drugs can make the illness milder and make
the patient feel better faster. They may also prevent serious flu
complications. For treatment, antiviral drugs work best if started soon
after getting sick (within 2 days of symptoms).

Preparedness
To
maintain a secure household during a pandemic flu, the Water Quality
& Health Council recommends keeping as supplies food and bottled
water, portable power sources and chlorine bleach as an emergency water
purifier and surface sanitizer.[36]

Epidemiology

Outbreaks in swine

2007 Philippine outbreak
On
August 20, 2007 Department of Agriculture officers investigated the
outbreak of swine flu in Nueva Ecija and Central Luzon, Philippines. The
mortality rate is less than 10% for swine flu, unless there are
complications like hog cholera. On July 27, 2007, the Philippine
National Meat Inspection Service (NMIS) raised a hog cholera "red alert"
warning over Metro Manila and 5 regions of Luzon after the disease
spread to backyard pig farms in Bulacan and Pampanga, even if these
tested negative for the swine flu virus.[37][38]

Outbreaks in humans
Swine
flu has been reported numerous times as a zoonosis in humans, usually
with limited distribution, rarely with a widespread distribution. The
1918 flu pandemic in humans was associated with H1N1,[39]
thus may reflect a zoonosis either from swine to humans or from humans
to swine. Evidence available from that time is not sufficient to resolve
this question. The "Spanish" influenza pandemic of 1918–19 infected one
third of the world's population (or around 500 million persons at that
time) and caused around 50 million deaths.[39]

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.[40]
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.[5]
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.[41] 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.[42][43]

2009 swine flu outbreak

Main article: 2009 swine flu outbreak

Confirmed cases followed by death Confirmed cases Unconfirmed or suspected cases See also: Live map of swineflu, H1N1 live map


The
new strain of influenza involved in the 2009 swine flu outbreak is a
reassortment of several strains of influenza A virus subtype H1N1 that
are, separately, endemic in humans and 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.[44]
The
origins of this new strain remain unknown. One theory is that Asian and
European strains traveled to Mexico in migratory birds or in people,
then combined with North American strains in Mexican pig factory farms
before jumping over to farm workers.[45]
The earliest
known human case was at a Mexican pig farm whose nearby neighbors had
been complaining about the manure smell and flies.[46] Edgar
Hernandez, 4, 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.[47]
The Mexican health agency
acknowledged that the original disease vector of the virus may have been
flies multiplying in manure lagoons of pig farms near Perote, Veracruz,
owned by Granjas Carroll,[48] a subsidiary of Smithfield Foods.[49]
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."[50] Pigs have been
shown to act as a potential "mixing vessel" in which reassortment can
occur between flu viruses of several species.[51][52] 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 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 H274Y by the swine flu via recombination or reassortment.
Swine H1N1 with human H1 and N1 have been reported.
The 1918
pandemic strain has 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.[53]
 الموضوع : Swine influenza   المصدر :منتديات تقى الإسلامية  الكاتب:  El Helalya

 توقيع العضو/ه:El Helalya

الرجوع الى أعلى الصفحة اذهب الى الأسفل

El Helalya
المؤسسة

المؤسسة
El Helalya


المشاركات :
22515


تاريخ التسجيل :
08/08/2008


الجنس :
انثى

البلد :
مصر

sms :
سبحان الله

ـــــــــــ


ــــــــــــــ


Swine influenza  _
مُساهمةموضوع: رد: Swine influenza    Swine influenza  Emptyالخميس 10 نوفمبر 2011 - 4:48 

thank you for this important subject

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Distribution Map

أنقر على الرابط لغرض عرض صورة مكبرة عن توزيع حالات المرض في كل أنحاء العالم
عدد الحالات في كل دولة مع عدد الوفيات


[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]
 الموضوع : Swine influenza   المصدر :منتديات تقى الإسلامية  الكاتب:  El Helalya

 توقيع العضو/ه:El Helalya

الرجوع الى أعلى الصفحة اذهب الى الأسفل

El Helalya
المؤسسة

المؤسسة
El Helalya


المشاركات :
22515


تاريخ التسجيل :
08/08/2008


الجنس :
انثى

البلد :
مصر

sms :
سبحان الله

ـــــــــــ


ــــــــــــــ


Swine influenza  _
مُساهمةموضوع: رد: Swine influenza    Swine influenza  Emptyالخميس 10 نوفمبر 2011 - 4:49 

المعلومات مأخوذة من موقع طبي حكومي أمريكي يسمى :
المراكز الأمريكية للسيطرة والوقاية من الأمراض .
centers for disease control and prevension
[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]
 الموضوع : Swine influenza   المصدر :منتديات تقى الإسلامية  الكاتب:  El Helalya

 توقيع العضو/ه:El Helalya

الرجوع الى أعلى الصفحة اذهب الى الأسفل

 

Swine influenza

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