Details About Swine Flu And Its Prevention

What is Swine Flu?;How To Prevent & Treatment Swine Flu ;History Of Swine Flu

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. People who work with swine, especially people with intense exposures, are at risk of catching swine influenza if the swine carry a strain able to infect humans. However, these strains rarely are able to pass from human to human. Rarely, SIV mutates into a form able to pass easily from human to human. The strain responsible for the 2009 swine flu outbreak is believed to have undergone such a mutation.

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 in a few days.

Of the three genera of human flu, two are endemic also in swine: Influenzavirus A (common) and Influenzavirus C (rare). 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. 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.

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 and 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 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 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.

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.

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.H3N2 evolved from H2N2 by antigenic shift. In August 2004, researchers in China found H5N1 in pigs.

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.

Signs and symptoms

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.

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." A diagnosis of confirmed swine flu requires laboratory testing of a respiratory sample (a simple nose and throat swab).
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).

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.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.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. 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.

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. 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.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. Diagnosis can be made by sending a specimen, collected during the first five days, to the CDC for analysis.

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.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.

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.

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.

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.Vaccines against the H1N1 strain in the 2009 human outbreak are being developed and could be ready as early as June 2009.

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. 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.
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.

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, 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.
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.
2009 swine flu outbreak

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.

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.

The earliest known human case was at a Mexican pig farm whose nearby neighbors had been complaining about the manure smell and flies.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. 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,a subsidiary of Smithfield Foods.
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 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

Eating fish cuts heart failure risk

Times Of India

Eating salmon or other fatty fish just once a week can help reduce men’s risk of heart failure, says a new study. However, the effect of fatty fish and marine omega-3 fatty acids can be seen only in men. The study provided no evidence that taking food supplements containing marine omega-3 fatty acids made any difference. The men in this study, which is published in Europe’s leading cardiology journal, the European Heart Journal, obtained most of their marine omega-3 fatty acids from the food they ate.

Researchers in the USA and Sweden followed 39,367 Swedish men, aged between 45-79, from 1998 to 2004. They recorded details of the men’s diet and tracked the men’s outcome through Swedish inpatient and cause-of-death registers. During the period, 597 men without a history of heart disease or diabetes developed heart failure, of which 34 died.

The researchers found that men who eat fatty fish, such as herring, mackerel, salmon, whitefish and char, once a week were 12 percent less likely to develop heart failure compared to men who never eat fatty fish.

Although this association with fatty fish did not reach statistical significance, the researchers also found a statistically significant association with the intake of marine omega-3 fatty acids (found in cod livers and other fish oils); men who consumed approximately 0.36 grams a day were 33 percent less likely to develop heart failure than men who consumed little or no marine omega-3 fatty acids (0.15-0.22 grams a day).

The men were divided into five groups depending on their intake of fatty fish, with the first group consuming none, or very little, and the fifth group consuming the most - three of more servings of fatty fish a week. The researchers found that while the middle group, which eat one serving of fatty fish a week, had a 12 percent reduced risk compared to the men who never eat fatty fish, the men in the next two groups, who eat either two servings a week or three or more servings a week, had nearly the same risk as the men who eat none.

The researchers also divided the men into five groups based on their intake of marine omega-3 fatty acids. Again, the same U-shape was seen, with the middle group who consumed 0.36 grams a day of fatty acids having a 33 percent reduced risk of heart failure, while the men who consumed more (either approximately 0.46 grams per day or approximately 0.71 grams per day) had a risk similar to men who consumed none or very little.

Dr Emily Levitan, a cardiology research fellow at Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, USA, who led the research, said: "Our study shows that a moderate intake of fatty fish and marine omega-3 fatty acids is associated with lower rates of heart failure in men, but that the men did not gain a greater benefit by eating more of these foods.

"The apparent U-shaped relationship of fatty fish and marine omega-3 fatty acids with heart failure was unexpected. The higher rate of heart failure in men who consumed the most fatty fish or marine omega-3 fatty acids compared with moderate consumption may be due to chance. Alternatively, these may be men in poor health who ate more fish to try to improve their ill-health, and therefore the fatty fish and fatty acids appear to be risk factors for heart failure. I suspect this is the most likely explanation, but we cannot be certain from our data."

Alcohol flush 'shows cancer risk'

BBC News

People who get a flushed face when they drink alcohol should be particularly wary of gullet cancer, experts warn.

About 8% of the population - mostly people of East Asian descent - have an enzyme deficiency that causes their skin to redden when they drink alcohol.

National Institute on Alcohol Abuse and Alcoholism research found even moderate drinkers with this deficiency were more at risk of oesophageal cancer.

The report authors told PLoS Medicine such people may benefit from screening.

Alcohol-induced flush is predominantly down to an inherited deficiency in an enzyme called aldehyde dehydrogenase 2 (ALDH2).

Although this is widely known, few are aware of the accumulating evidence that ALDH2-deficient individuals are at much higher risk of oesophageal cancer from alcohol consumption, say the researchers.

Dr Philip Brooks and his team from the National Institute on Alcohol Abuse and Alcoholism, working with Japanese colleagues, assessed how big the extra risk is.

They found individuals with one copy of the inactive gene causing ALDH2-deficiency were 6-10 times more likely to develop oesophageal cancer than individuals with the fully active ALDH2 enzyme who drank comparable amounts of alcohol.

They said if moderate or heavy drinking people with this deficiency were to become light drinkers instead, 53% of oesophageal cancers might be prevented among Japanese men.

They based their calculations on light consumption being fewer than 25 UK units of alcohol per week, moderate being fewer than 50 UK units and heavy being more than 50 UK units per week.

Raising awareness

In the UK, a unit of alcohol is 8g and the Department of Health recommends men should not drink more than three to four units of alcohol a day, and women should drink no more than two to three.

Dr Brooks said: "Cancer of the oesophagus is particularly deadly, with five-year survival rates ranging from 12% to 31% throughout the world.

"And we estimate that at least 540 million people have this alcohol-related increased risk for oesophageal cancer.

"We hope that, by raising awareness of this important public health problem, affected individuals who drink will reduce their cancer risk by limiting their alcohol consumption."

He said doctors could determine ALDH2 deficiency simply by asking about previous episodes of flushing.

Then people could be counselled to reduce alcohol consumption, and those high-risk patients could be assessed for endoscopic cancer screening.

Oliver Childs, of the charity Cancer Research UK, said: "We know that drinking alcohol increases the risk of several different cancers, and that the more you cut down on your drinking, the more you reduce your cancer risk.

"This research helps us better understand how our environment and genes work in tandem to influence our risk of cancer."