How did swine flu spread from pigs to humans

how did swine flu spread from pigs to humans

What People Who Raise Pigs Need To Know About Influenza (Flu)

Spread of flu viruses between pigs and people is thought to occur in one of three ways: not available, use an alcohol-based hand main way is when an infected pig (or person) coughs or sneezes, and droplets containing virus spread through the Size: 1MB. May 02, The cause was a type of H1N1 that was a close match to the Wisconsin strain, and may have been spread from human to Newsweek Staff.

Note: This page contains background information about swine influenza infections in pigs. For information about human seasonal influenza, visit the CDC seasonal flu website. Swine Influenza swine flu what is a discussion in science a respiratory disease of pigs caused by type A influenza virus that regularly causes outbreaks of influenza in pigs.

Swine flu viruses do not usually infect humans, but rare human infections have occurred. For more information about swine influenza infections in humans, see Variant Influenza Viruses in Humans. Swine flu viruses can cause high levels of illness in pig herds, but cause few deaths in pigs. Swine influenza viruses can circulate among swine throughout the year, but most outbreaks occur during the late fall and winter months similar to outbreaks in humans.

Like influenza viruses in humans and other animals, swine flu viruses change constantly. Pigs can be infected by avian influenza and human influenza viruses as well as swine influenza viruses. When influenza viruses from different species infect pigs, the viruses can reassort i. Over the years, different variations of swine flu viruses have emerged. Swine flu viruses are thought to be spread among pigs mostly through close contact and possibly from contaminated objects moving between infected and uninfected pigs.

Infected swine herds, including those vaccinated against swine flu, may have sporadic disease, or may show only mild or no symptoms of infection. Signs of swine flu in pigs can include fever, depression, coughing barkingdischarge from the nose or eyes, sneezing, breathing difficulties, eye redness or inflammation, and going off feed. Some pigs infected with influenza, however, may show no signs of illness at all.

H1N1 and H3N2 swine flu viruses are endemic among pig populations in the United States and something that the industry deals with routinely. Outbreaks among pigs normally occur in colder weather months late fall and winterbut can occur year round. While H1N1 swine viruses have been known to circulate among pig populations since at leastH3N2 influenza viruses did not begin circulating among pigs in the United States until about The H3N2 viruses initially were introduced into the pig population from humans.

However, since then the H3N2 viruses circulating in pigs have changed. The H3N2 viruses circulating in pigs now are very different from the seasonal H3N2 viruses that circulate in humans. Just as there are influenza vaccines for people, there are specific swine influenza vaccines available for pigs.

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Apr 23, How does swine flu spread? Influenza viruses can be directly transmitted from pigs to people and from people to pigs. Human infection with flu viruses from pigs are most likely to occur when people are in close proximity to infected pigs, such as in pig barns and livestock exhibits housing pigs at fairs. Human-to-human transmission of swine flu can. Nov 25, The mixing of influenza genes in pigs can result in the emergence of viruses with pandemic potential in humans. Improved surveillance of influenza in pigs and other animals may help to detect the emergence of influenza viruses with the potential to cause illness and spread among people, possibly resulting in a pandemic. Sep 07, While it is now accepted that the swine flu pandemic was caused by H1N1 jumping from pigs to humans, what happened to the virus next is not often considered.

The swine flu pandemic was an influenza pandemic that lasted about 19 months, from January to August , and was the most recent flu pandemic involving H1N1 influenza virus the first being the Spanish flu pandemic and the second being the Russian flu. Some studies estimated that the actual number of cases including asymptomatic and mild cases could be million to 1.

The number of lab-confirmed deaths reported to the World Health Organization WHO is 18,, [10] though the H1N1 flu pandemic is estimated to have actually caused about , range from , to , deaths. This manifests itself as increased breathing difficulty and typically occurs three to six days after initial onset of flu symptoms. A November New England Journal of Medicine article recommended that flu patients whose chest X-ray indicates pneumonia receive both antivirals and antibiotics.

The World Health Organization uses the term " H1N1 pandemic" when referring to the event, and officially adopted the name "A H1N1 pdm09" for the virus in , after the conclusion of the pandemic. Controversy arose early on regarding the wide assortment of terms used by journalists, academics, and officials. Labels like "H1N1 flu", "Swine flu", "Mexican flu", and variations thereof were typical.

Criticism centered on how these names may confuse or mislead the public. It was argued that the names were overly technical e. Some academics of the time asserted there is nothing wrong with such names, [27] while research published years later in concluded that Mexican Americans and Latino Americans had indeed been stigmatized due to the frequent use of term "Mexican flu" in the news media. Official entities adopted terms with varying consistency over the course of the pandemic. Officials in Taiwan suggested use of the names "H1N1 flu" or "new flu".

Officials in Israel and South Korea briefly considered adoption of the name "Mexican virus" due to concern about the use of the word "swine". As terminology changed to deal with these and other such issues, further criticism was made that the situation was unnecessarily confusing.

Analysis of the genetic divergence of the virus in samples from different cases indicated that the virus jumped to humans in , probably after June, and not later than the end of November, [35] likely around September Initially called an "outbreak", widespread H1N1 infection was first recognized in the state of Veracruz , Mexico, with evidence that the virus had been present for months before it was officially called an "epidemic". The new virus was first isolated in late April by American and Canadian laboratories from samples taken from people with flu in Mexico, Southern California, and Texas.

Soon the earliest known human case was traced to a case from 9 March in a 5-year-old boy in La Gloria, Mexico, a rural town in Veracruz. CDC stopped counting cases and declared the outbreak a pandemic. Despite being informally called "swine flu", the H1N1 flu virus cannot be spread by eating pork products; [43] [44] similar to other influenza viruses, it is typically contracted by person to person transmission through respiratory droplets.

The pandemic began to taper off in November , [48] and by May , the number of cases was in steep decline.

The majority of these deaths occurred in Africa and Southeast Asia. Experts, including the WHO, have agreed that an estimated , people were killed by the disease, much higher than the initial death toll.

The symptoms of H1N1 flu are similar to those of other influenzas , and may include fever, cough typically a "dry cough" , headache, muscle or joint pain, sore throat , chills , fatigue , and runny nose. Diarrhea , vomiting, and neurological problems have also been reported in some cases. In September , the CDC reported that the H1N1 flu "seems to be taking a heavier toll among chronically ill children than the seasonal flu usually does". The World Health Organization reports that the clinical picture in severe cases is strikingly different from the disease pattern seen during epidemics of seasonal influenza.

While people with certain underlying medical conditions are known to be at increased risk, many severe cases occur in previously healthy people. In severe cases, patients generally begin to deteriorate around three to five days after symptom onset. Deterioration is rapid, with many patients progressing to respiratory failure within 24 hours, requiring immediate admission to an intensive care unit.

Upon admission, most patients need immediate respiratory support with mechanical ventilation. Most complications have occurred among previously unhealthy individuals, with obesity and respiratory disease as the strongest risk factors.

Pulmonary complications are common. Primary influenza pneumonia occurs most commonly in adults and may progress rapidly to acute lung injury requiring mechanical ventilation. Secondary bacterial infection is more common in children. Staphylococcus aureus , including methicillin-resistant strains, is an important cause of secondary bacterial pneumonia with a high mortality rate; Streptococcus pneumoniae is the second most important cause of secondary bacterial pneumonia for children and primary for adults.

Neuromuscular and cardiac complications are unusual but may occur. Non-white and pregnant patients were over-represented. Three out of the four cases of H1N1-associated myocarditis were classified as fulminant, and one of the patients died.

An article published in JAMA in September [74] challenged previous reports and stated that children infected in the flu pandemic were no more likely to be hospitalised with complications or get pneumonia than those who catch seasonal strains. Researchers found that about 1. Confirmed diagnosis of pandemic H1N1 flu requires testing of a nasopharyngeal , nasal, or oropharyngeal tissue swab from the patient.

CDC recommend testing only for people who are hospitalized with suspected flu, pregnant women, and people with weakened immune systems. It uses a molecular biology technique to detect influenza A viruses and specifically the H1N1 virus. The new test will replace the previous real-time RT-PCR diagnostic test used during the H1N1 pandemic, which received an emergency use authorization from the U.

Food and Drug Administration in April The virus was found to be a novel strain of influenza for which existing vaccines against seasonal flu provided little protection. A study at the U. Centers for Disease Control and Prevention published in May found that children had no preexisting immunity to the new strain but that adults, particularly those older than 60, had some degree of immunity.

Analyses of the genetic sequences of the first isolates, promptly shared on the GISAID database according to Nature and WHO, [85] [86] soon determined that the strain contains genes from five different flu viruses: North American swine influenza, North American avian influenza, human influenza, and two swine influenza viruses typically found in Asia and Europe. Further analysis has shown that several proteins of the virus are most similar to strains that cause mild symptoms in humans, leading virologist Wendy Barclay to suggest on 1 May , that the initial indications are that the virus was unlikely to cause severe symptoms for most people.

The virus was less lethal than previous pandemic strains and killed about 0. With deaths of 1, children and 7, adults 18 to 64, these figures were deemed "much higher than in a usual flu season" during the pandemic.

In June , scientists from Hong Kong reported discovery of a new swine flu virus: a hybrid of the pandemic H1N1 virus and viruses previously found in pigs. It was the first report of a reassortment of the pandemic virus, which in humans had been slow to evolve.

Nancy Cox , head of the influenza division at the U. Centers for Disease Control and Prevention, has said, "This particular paper is extremely interesting because it demonstrates for the first time what we had worried about at the very onset of the pandemic, and that is that this particular virus, when introduced into pigs, could reassort with the resident viruses in pigs and we would have new gene constellations.

And bingo, here we are. When pigs become simultaneously infected with more than one virus, the viruses can swap genes, producing new variants which can pass to humans and sometimes spread amongst them.

With pigs it's very much a two-way street. Spread of the H1N1 virus is thought to occur in the same way that seasonal flu spreads. Flu viruses are spread mainly from person to person through coughing or sneezing by people with influenza. Sometimes people may become infected by touching somethingsuch as a surface or objectwith flu viruses on it and then touching their face. The basic reproduction number the average number of other individuals whom each infected individual will infect, in a population which has no immunity to the disease for the novel H1N1 is estimated to be 1.

Most transmissions occur soon before or after the onset of symptoms. The H1N1 virus has been transmitted to animals, including swine , turkeys , ferrets , household cats, at least one dog, and a cheetah. Because the H1N1 vaccine was initially in short supply in the U. Although it was initially thought that two injections would be required, clinical trials showed that the new vaccine protected adults "with only one dose instead of two;" thus the limited vaccine supplies would go twice as far as had been predicted.

Officials also urged communities, businesses, and individuals to make contingency plans for possible school closures, multiple employee absences for illness, surges of patients in hospitals, and other effects of potentially widespread outbreaks. The vaccine will protect against the H1N1 pandemic virus and two other flu viruses. On 27 April , the European Union health commissioner advised Europeans to postpone nonessential travel to the United States or Mexico.

This followed the discovery of the first confirmed case in Spain. The system was expected to reduce the burden on general practitioners. President Obama declared swine flu a national emergency, giving Secretary of Health and Human Services Kathleen Sebelius authority to grant waivers to requesting hospitals from usual federal requirements. By 19 November , doses of vaccine had been administered in over 16 countries. A review by the U. The effectiveness was based on European and Asian studies and expert opinion.

The delay in vaccine administration demonstrated the shortcomings of the world's capacity for vaccine-production, as well as problems with international distribution. Some manufacturers and wealthy countries had concerns regarding liability and regulations, as well as the logistics of transporting, storing, and administering vaccines to be donated to poorer countries. In January , Wolfgang Wodarg , a German deputy who trained as a physician and chaired the health committee at the Council of Europe , claimed that major firms had organized a "campaign of panic" to put pressure on the World Health Organization WHO to declare a "false pandemic" to sell vaccines.

Wodarg said the WHO's "false pandemic" flu campaign is "one of the greatest medicine scandals of the century". He said that the "false pandemic" campaign began in May in Mexico City , when a hundred or so "normal" reported influenza cases were declared to be the beginning of a threatening new pandemic, although he said there was little scientific evidence for it.

Nevertheless, he argued that the WHO, "in cooperation with some big pharmaceutical companies and their scientists, re-defined pandemics," removing the statement that "an enormous amount of people have contracted the illness or died" from its existing definition and replacing it by stating simply that there has to be a virus, spreading beyond borders and to which people have no immunity.

The WHO responded by stating that they take their duty to provide independent advice seriously and guarded against interference from outside interests. We expect and indeed welcome criticism and the chance to discuss it". The description of it as a fake is wrong and irresponsible". On 12 April , Keiji Fukuda, the WHO's top influenza expert, stated that the system leading to the declaration of a pandemic led to confusion about H1N1 circulating around the world and he expressed concern that there was a failure to communicate in regard to uncertainties about the new virus, which turned out to be not as deadly as feared.

She told them, "We want a frank, critical, transparent, credible and independent review of our performance. In June , Fiona Godlee , editor-in-chief of the BMJ , published an editorial which criticised the WHO, saying that an investigation had disclosed that some of the experts advising WHO on the pandemic had financial ties with drug companies which were producing antivirals and vaccines.

The bottom line, however, is that decisions to raise the level of pandemic alert were based on clearly defined virological and epidemiological criteria. It is hard to bend these criteria, no matter what the motive".

On 7 May , the WHO stated that containment was not feasible and that countries should focus on mitigating the effect of the virus. They did not recommend closing borders or restricting travel. According to studies conducted in Australia and Japan, screening individuals for influenza symptoms at airports during the H1N1 outbreak was not an effective method of infection control. Rather than closing schools, the CDC recommended that students and school workers with flu symptoms should stay home for either seven days total, or until 24 hours after symptoms subsided, whichever was longer.

They also urged schools to suspend rules, such as penalties for late papers or missed classes or requirements for a doctor's note, to enforce "self-isolation" and prevent students from venturing out while ill; [] schools were advised to set aside a room for people developing flu-like symptoms while they waited to go home and to have ill students or staff and those caring for them use face masks.

In California, school districts and universities were on alert and worked with health officials to launch education campaigns. Many planned to stockpile medical supplies and discuss worst-case scenarios, including plans to provide lessons and meals for low-income children in case elementary and secondary schools closed.

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