Swine flu

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Swine flu (swine influenza) is a respiratory disease caused by viruses (influenza viruses) that infect the respiratory tract of pigs, resulting in nasal secretions, a barking cough, decreased appetite, and listless behavior. Swine flu produces most of the same symptoms in pigs as human flu produces in people. Swine flu can last about one to two weeks in pigs that survive. Swine influenza virus was first isolated from pigs in 1930 in the U.S. and has been recognized by pork producers and veterinarians to cause infections in pigs worldwide. In a number of instances, people have developed the swine flu infection when they are closely associated with pigs (for example, farmers, pork processors), and likewise, pig populations have occasionally been infected with the human flu infection. In most instances, the cross-species infections (swine-origin virus to man; human flu virus to pigs) have remained in local areas and have not caused national or worldwide infections in either pigs or humans. Unfortunately, this cross-species situation with influenza viruses (human infections with swine viruses) has had the potential to change. Investigators decided the 2009 so-called “swine flu” strain, first seen in Mexico, should be termed novel H1N1 flu since it was mainly found infecting people and exhibits two main surface antigens, H1 (hemagglutinin type 1) and N1 (neuraminidase type1). The eight RNA strands from novel H1N1 flu have one strand derived from human flu strains, two from avian (bird) strains, and five from swine strains.

The main swine flu viruses in pigs in recent years are swine triple reassortant (tr; it means a viral strain with genes from three different organisms) H1N1, trH3N2, and trH1N2. However, in August 2018, China first reported a new swine flu outbreak in pigs in Liaoning province. The pig flu strain is known as African swine flu (although some researchers think it originated in Russia), almost 100% fatal to pigs, was the cause. This strain is highly infectious, survives in heat and cold environments, and can remain viable and infectious on surfaces for days to weeks. Currently, there is no effective vaccine or drug to stop its spread, so the disease is treated by the immediate slaughter of infected pigs. China has about 50% of the world’s pig population and relies on pork to provide a large amount of protein for the Chinese population. Culling the pig population in China may result in China needing to import pork that would likely be a large economic blow to China’s economy. This virus has not yet been detected in the U.S. This flu strain reportedly does not spread to humans.

How is swine flu transmitted? Is swine flu contagious?

Swine influenza is transmitted from person to person by inhalation or ingestion of droplets containing virus from people sneezing or coughing; it is not transmitted by eating cooked pork products. The newest swine flu virus that has caused swine flu is influenza A H3N2v (commonly termed H3N2v) that began as an outbreak in 2011. The “v” in the name means the virus is a variant that normally infects only pigs but has begun to infect humans. There have been small outbreaks of H1N1 influenza since the pandemic; a recent one is in India where at least three people have died.

What is the incubation period for swine flu?

The incubation period for swine flu is about one to four days, with the average being two days; in some people, the incubation period may be as long as about seven days in adults and children.

What is the contagious period for swine flu?

The contagious period (human-to-human viral infection) for swine influenza in adults usually begins one day before symptoms develop in an adult and it lasts about five to seven days after the person becomes sick. However, people with weakened immune systems and children may be contagious for a longer period of time (for example, about 10 to 14 days).

How long does the swine flu last?

In uncomplicated infections, swine flu typically begins to resolve after three to seven days, but the malaise and cough can persist two weeks or more in some patients. Severe swine flu may require hospitalization that increases the length of time of infection to about nine to 10 days.

What causes swine flu?

The cause of the 2009 swine flu was an influenza A virus type designated as H1N1. In 2011, a new swine flu virus was detected. The new strain was named influenza A (H3N2)v. Only a few people (mainly children) were first infected, but officials from the U.S. Centers for Disease Control and Prevention (CDC) reported increased numbers of people infected in the 2012-2013 flu season. Currently, there are not large numbers of people infected with H3N2v. Unfortunately, another virus termed H3N2 (note no “v” in its name) has been detected and caused flu, but this strain is different from H3N2v. In general, all of the influenza A viruses have a structure similar to the H1N1 virus; each type has a somewhat different H and/or N structure

What are swine flu symptoms and signs?

Symptoms of swine flu are similar to most influenza infections: fever (100 F or greater), cough (usually dry), nasal secretions, fatigue, and headache, with fatigue being reported in most infected individuals. Some patients may also get a sore throat, rash, body (muscle) aches or pains, headaches, chills, nausea, vomiting, and diarrhea. In Mexico, many of the initial patients infected with H1N1 influenza were young adults, which made some investigators speculate that a strong immune response, as seen in young people, may cause some collateral tissue damage. The incubation period from exposure to first symptoms is about one to four days, with an average of two days. The symptoms last about one to two weeks and can last longer if the person has a severe infection.

Some patients develop severe respiratory symptoms, such as shortness of breath, and need respiratory support (such as a ventilator to breathe for the patient). Patients can get pneumonia (bacterial secondary infection) if the viral infection persists, and some can develop seizures. Death often occurs from secondary bacterial infection of the lungs; appropriate antibiotics need to be used in these patients. The usual mortality (death) rate for typical influenza A is about 0.1%, while the 1918 “Spanish flu” epidemic had an estimated mortality rate ranging from 2%-20%. Swine (H1N1) flu in Mexico had about 160 deaths and about 2,500 confirmed cases, which would correspond to a mortality rate of about 6%, but these initial data were revised and the mortality rate worldwide was estimated to be much lower. Fortunately, the mortality rate of H1N1 remained low and similar to that of the conventional flu (average conventional flu mortality rate is about 36,000 per year; projected H1N1 flu mortality rate was 90,000 per year in the U.S. as determined by the president’s advisory committee, but it never approached that high number).

Fortunately, although H1N1 developed into a pandemic (worldwide) flu strain, the mortality rate in the U.S. and many other countries only approximated the usual numbers of flu deaths worldwide. Speculation about why the mortality rate remained much lower than predicted includes increased public awareness and action that produced an increase in hygiene (especially hand washing), the fairly rapid development of a new vaccine, and patient self-isolation if symptoms developed.

What types of health care professionals treat swine flu?

Almost all uncomplicated patients with swine flu can be treated at home or by the patient’s pediatrician, primary care provider, or emergency-medicine doctor. For more complicated and/or severe swine flu infections, specialists such as critical care specialists, lung specialists (pulmonologists), and infectious-disease specialists may be consulted.

What tests do health care professionals use to diagnose swine flu?

Swine flu is presumptively diagnosed clinically by the patient’s history of association with people known to have the disease and their symptoms listed above. Usually, a quick test (for example, a nasopharyngeal swab sample) is done to see if the patient is infected with the influenza A or B virus. Most of the tests can distinguish between A and B types. The test can be negative (no flu infection) or positive for type A and B. If the test is positive for type B, the flu is not likely to be swine flu. If it is positive for type A, the person could have a conventional flu strain or swine flu. However, the accuracy of these tests has been challenged, and the U.S. Centers for Disease Control and Prevention (CDC) has not completed their comparative studies of these tests. However, a new test developed by the CDC and a commercial company reportedly can detect H1N1 reliably in about one hour; the test was formerly only available to the military. In 2010, the FDA approved a commercially available test that could detect H1N1 within four hours. Most of these rapid tests are based on PCR technology.

Swine flu is definitively diagnosed by identifying the particular antigens (surface proteins) associated with the virus type. In general, this test is done in a specialized laboratory and is not done by many doctors’ offices or hospital laboratories. However, doctors’ offices are able to send specimens to specialized laboratories if necessary. Because of the large number of novel H1N1 swine flu cases that occurred in the 2009-2010 flu season (the vast majority of flu cases [about 95%-99%] were due to novel H1N1 flu viruses), the CDC recommended only hospitalized patients’ flu virus strains be sent to reference labs to be identified. H3N2v flu strains and other flu virus strains are diagnosed with similar methods.

What is the treatment for swine flu?

The best treatment for influenza infections in humans is prevention by vaccination. Work by several laboratories has produced vaccines. The first H1N1 vaccine released in early October 2009 was a nasal spray vaccine that was approved for use in healthy individuals ages 2-49. However, the use of nasal spray has not been recommended since 2016. The injectable vaccine, made from killed H1N1, became available in the second week of October 2009. This vaccine was approved for use in ages 6 months to the elderly, including pregnant females. The CDC approved both of these vaccines only after they had conducted clinical trials to prove that the vaccines were safe and effective

What is the history of swine flu in humans?

In 1976, there was an outbreak of swine flu at Fort Dix. This virus was not the same as the 2009 H1N1 outbreak, but it was similar insofar as it was an influenza A virus that had similarities to the swine flu virus. There was one death at Fort Dix. The government decided to produce a vaccine against this virus, but the vaccine was associated with rare instances of neurological complications (Guillain-Barré syndrome) and was discontinued. Some individuals speculate that formalin, used to inactivate the virus, may have played a role in the development of this complication in 1976. One of the reasons it takes a few months to develop a new vaccine is to test the vaccine for safety to avoid the complications seen in the 1976 vaccine. Individuals with active infections or diseases of the nervous system are also not recommended to get flu vaccines.

Early in the spring of 2009, the H1N1 flu virus was first detected in Mexico, causing some deaths among a “younger” population. It began increasing during the summer 2009 and rapidly circulated to the U.S. and to Europe and eventually worldwide. The WHO declared it first fit their criteria for an epidemic and then, in June 2009, the WHO declared the first flu pandemic in 41 years. There was a worldwide concern and people began to improve in hand washing and other prevention methods while they awaited vaccine development. The trivalent vaccine made for the 2009-2010 flu season offered virtually no protection from H1N1. New vaccines were developed (both live and killed virus) and started to become available in September 2009-October 2009. The CDC established a protocol guideline for those who should get the vaccine first. By late December to January, a vaccine against H1N1 was available in moderate supply worldwide. The numbers of infected patients began to recede and the pandemic ended. However, a strain of H1N1 was incorporated into the yearly trivalent vaccine for the 2010-2011 flu season because the virus was present in the world populations.

As stated in the first section of this article, a new strain of swine flu, (H3N2)v, was detected in 2011; it has not affected any large numbers of people in the current flu season. However, another antigenically distinct virus with the same H and N components (termed H3N2 (note no “v”) has caused flu in humans; viral antigens were incorporated into the 2013-2014 seasonal flu shots and nasal spray vaccines.

In India in 2015-2016, a large outbreak of swine flu killed more than 1,900 people. During 2016, the number of infected people and deaths due to swine flu dropped, but now in 2017, there is a marked resurgence of the disease. The new outbreak of swine flu that began in January 2017 has resulted in 22,186 people being diagnosed with the infection. There have been 1,094 recorded deaths in 8 months, and the spread of the infection shows no signs of slowing. In the first three weeks of August 2017, 342 deaths were due to swine flu. Unfortunately, private hospitals and clinics do not have to report the number of swine flu diagnoses or deaths, so it is possible according to one medical director of a private clinic, that the current statistics represent “possibly just the tip of the iceberg.” In the U.S., the 2017-2018 flu season was termed a high severity season by the CDC because an estimated 80,000 people died of flu and its complications.

What are the risk factors for swine flu?

Vaccination to prevent influenza is particularly important for people who are at increased risk for severe complications from influenza or at higher risk for an influenza-related doctor or hospital visits. When vaccine supply is limited, vaccination efforts should focus on delivering vaccination to the following people since these populations have a higher risk for H1N1 and some other viral infections according to the CDC:

  1. All children 6 months to 4 years (59 months) of age
  2. All people 50 years of age and older
  3. Adults and children who have chronic pulmonary (including asthma) or cardiovascular (except isolated hypertension), renal, hepatic, neurological, hematologic, or metabolic disorders (including diabetes mellitus)
  4. People who have immunosuppression (including immunosuppression caused by medications or by HIV)
  5. Women who are or will be pregnant during the influenza season
  6. Children and adolescents (6 months to 18 years of age) who are receiving long-term aspirin therapy and who might be at risk for experiencing Reye syndrome after influenza virus infection
  7. Residents of nursing homes and other long-term care facilities
  8. American Indians/Alaska natives
  9. People who are morbidly obese (BMI ≥40)
  10. Health care professionals (doctors, nurses, health care personnel treating patients)
  11. Household contacts and caregivers of children under 5 years of age and adults 50 years of age and older, with particular emphasis on vaccinating contacts of children less than 6 months age
  12. Household contacts and caregivers of people with medical conditions that put them at higher risk for severe complications from influenza

Is it possible to prevent swine flu with a vaccine?

The CDC recommends for the 2018-2019 flu season that everyone 6 months old and older should get a flu shot to prevent or reduce the chance of getting the flu. The best way to prevent novel H1N1 swine flu is vaccination. The CDC recommendations that apply to H1N1, H3N2, and other flu viruses are almost identical to those above-mentioned recommendations for patients at risk when vaccine doses are limited and are as follows:

  1. Are aged 6 months through 4 years (59 months)
  2. Are aged 50 years and older
  3. Have chronic pulmonary (including asthma), cardiovascular (except hypertension), renal, hepatic, neurologic, hematologic, or metabolic disorders (including diabetes mellitus)
  4. Are immunosuppressed (including immunosuppression caused by medications or by human immunodeficiency virus)
  5. Are or will be pregnant during the influenza season
  6. Are aged 6 months through 18 years and receiving long-term aspirin therapy and who therefore might be at risk for experiencing Reye’s syndrome after influenza virus infection
  7. Are residents of nursing homes and other chronic-care facilities
  8. Are American Indians/Alaska Natives
  9. Are morbidly obese (body-mass index is 40 or greater)
  10. Are health care personnel
  11. Are household contacts and caregivers of children aged younger than 5 years and adults aged 50 years and older, with particular emphasis on vaccinating contacts of children aged younger than 6 months
  12. Are household contacts and caregivers of people with medical conditions that put them at higher risk for severe complications from influenza
  13. As in previous recommendations, all children aged 6 months to 8 years of age who receive a seasonal influenza vaccine for the first time should receive two doses. Children who received only one dose of a seasonal influenza vaccine in the first influenza season should receive two doses rather than one in the following influenza season.
  14. A newly approved inactivated trivalent vaccine containing 60 mcg of hemagglutinin antigen per influenza vaccine virus strain (Fluzone High-Dose [Sanofi Pasteur]) is an alternative inactivated vaccine for people 65 years of age and older.

The CDC occasionally makes changes and updates its information on vaccines and other recommendations about any current flu pandemics. The CDC states, “for the most accurate health information, visit http://www.cdc.gov or call 1-800-CDC-INFO, 24/7.” Caregivers should check the vaccine package inserts for more detailed information on the vaccines when they become available.

The CDC says that a good way to prevent any flu disease is to avoid exposure to the virus; this is done by frequent hand washing, not touching your hands to your face (especially the nose and mouth), and avoiding any close proximity to or touching any person who may have flu symptoms. Since the virus can remain viable and infectious for about 48 hours on many surfaces, good hygiene and cleaning with soap and water or alcohol-based hand disinfectants are also recommended. Some physicians say face masks may help prevent getting airborne flu viruses (for example, from a cough or sneeze), but others think the better use for masks would be on those people who have symptoms and sneeze or cough.

The use of Tamiflu, Relenza, or other antivirals may help prevent the flu if taken before symptoms develop or reduce symptoms if taken within about 48 hours after symptoms develop. Some investigators say that the administration of these drugs is still useful after 48 hours, especially in high-risk patient populations. However, taking these drugs is not routinely recommended for prevention for the healthy population because investigators suggest that as occurs with most drugs, flu strains will develop resistance to these medications. During the H1N1 pandemic, the CDC made further suggestions about the use of these antiviral medications and developed the interim guidelines for use of Tamiflu, Relenza, and recently updated information for new antivirals peramivir (Rapivab) and Xofluza as follows:

  1. Patients with high-risk factors should discuss flu symptoms and when to use antiviral medications; doctors should provide a prescription for the antiviral drug for the patient to use if the patient is exposed to flu or develops flu-like symptoms without having to go in to see the doctor.
  2. “Watchful waiting” was added as a response to taking antiviral medications, with the emphasis on the fact that those people who develop a fever and have a preexisting health condition should then begin the antiviral medication.
  3. The antiviral medications are the first-line medicines for the treatment of novel H1N1, H3N2, and H3N2v flu, and many viruses are to date susceptible to Tamiflu, Relenza, Rapivab, and Xofluza.

In general, people who have symptoms often undertake preventive measures to prevent the spread of flu. Symptomatic people should stay at home, avoid crowds, and take off from work or school until the disease is no longer transmittable (about two to three weeks) or until medical help and advice are sought. Sneezing, coughing, and nasal secretions need to be kept away from other people; simply using tissues and disposing of them will help others. Quarantining patients is usually not warranted, but such measures depend on the severity of the disease. The CDC recommends that people who appear to have an influenza-like illness upon arrival at work or school or become ill during the day be promptly separated from other people and be advised to go home until at least 24 hours after they are free of fever (100 F [37.8 C] or greater), or signs of a fever, without the use of fever-reducing medications. The novel H1N1 swine flu disease takes about seven to 10 days before fevers stop, but research data suggests waiting until the cough is gone since many people are still infectious about one week after the fever is gone. However, the CDC did not extend their recommendations to stay home for that extra we

Are there home remedies for swine flu?

An array of Herbs and spices with a motar and pestle.

There are many flu “cures” and “treatments” described on the Internet (for example, how cayenne pepper, menthol, or ginseng can be used to treat the flu); before using any of these substances, check with a doctor. However, there are many over-the-counter medications, such as naproxen (Aleve), ibuprofen (Advil and others) and acetaminophen (Tylenol), to reduce fever and discomfort, lozenges to soothe a sore throat, and decongestants to help manage mucus production and coughing. These medications help manage flu symptoms but do not cure the viral disease.

Was swine flu (H1N1) a cause of an epidemic or pandemic in the 2009-2010 flu season?

Yes. An epidemic is defined as an outbreak of a contagious disease that is rapid and widespread, affecting many individuals at the same time. The swine flu outbreak in Mexico fits this definition. A pandemic is an epidemic that becomes so widespread that it affects a region, continent, or the world. On June 11, 2009, WHO officials determined that H1N1 2009 influenza the swine flu reached WHO level 6 criteria (person-to-person transmission in two separate WHO-determined world regions) and declared a swine flu pandemic, the first flu pandemic in 41 years. The H1N1 flu reached over 200 different countries on every continent except Antarctica in the 2009-2010 flu season; fortunately, the severity of the disease did not increase. The following is the CDC data for mortality and morbidity of the 2009 epidemic in the U.S.: Final estimates were published in 2011 and state that from April 12, 2009, to April 10, 2010, approximately 60.8 million cases (range: 43.3-89.3 million), 274,304 hospitalizations (195,086-402,719), and 12,469 deaths (8,868-18,306) occurred in the United States due to H1N1. An outbreak in India that became widespread in that country lasted until late 2016. However, in 2017 another outbreak occurred.

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