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Swine Influenza Swine Flu H1N1 Fever

Swine Influenza, Swine Flu or H1N1

Definition of Swine Flu: Swine flu generally refers to swine influenza which is an acute, infectious respiratory disease of pigs.

Meaning of Swine Flu: Swine influenza is an acute, infectious respiratory disease of pigs. It is characterized by a sudden onset, coughing, difficulty breathing, fever and rapid turnaround. Swine flu is caused by influenza A virus (influenza A virus), usually between pigs, and is highly contagious but usually does not cause death. Autumn and winter is a high incidence period, but can be spread throughout the year. Swine flu is often recognized as one of the subtypes of influenza C virus (influenza C virus) or influenza A virus. The virus can cause influenza outbreaks in pigs. Generally, humans are rarely infected with swine flu virus.

Disease name:    Swine Influenza
Medical Name: H1N1 / Swine Influenza

Emerge:    Pig

Types of Illness: Flu

Table of Content

    1 Introduction to swine influenza virus

    2 History

    3 Clinical symptoms

    4 Pathology

     5 Diagnosis

    6 Categories

    ▪ Influenza C

    ▪ Influenza A

    7 Preventive measures

     8 Alert level of swine flu

    9 people infected with swine flu

    ▪ Symptoms

    ▪ Spread

    ▪ Susceptible people

    ▪ Incubation period

    ▪ Prevention

    ▪ Treatment

Introduction to swine flu virus

Swine influenza virus is a positive mucous virus in swine that can cause endemic influenza. The World Health Organization renamed the new deadly virus previously known as swine flu H1N1 influenza A on April 30, 2009. 

Swine influenza is a highly contagious infectious disease of the respiratory system of pigs, which is characterized by a sudden onset, sudden fever and other symptoms of colds, and recovers as fast as it occurs. 

Swine influenza is caused by an influenza virus and belongs to the same genus of influenza virus that infects humans. This virus has the characteristics of co-infection by humans and animals. Swine influenza in pigs is usually related to the introduction of new pigs on the farm.

Influenza A H1N1 virus is an influenza A virus, carrying the H1N1 subtype swine influenza virus strain, containing ribonucleic acid gene fragments of three influenza viruses, avian influenza, swine influenza and human influenza. It also has Asian swine flu and African swine Influenza virus characteristics.

There are many different types of influenza A, including:
Subtypes of influenza A viruses can cause influenza A H1N1 infection. 

Unlike bird flu, H1N1 flu can spread from person to person. There have been human infections with H1N1 flu in the past, but there have been no cases of human-to-human transmission.

What is the History of Swine Flu Virus?

Swine flu was first identified as a human flu-related illness during the 1918 outbreak, when pigs and humans developed the disease at the same time.

Ten years later, in 1930, it was first confirmed that it was an influenza virus that caused swine disease. For the next six decades, almost all swine flu strains were H1N1.

Then, from 1997 to 2002, three new strains of different subtypes and five different prototypes emerged as the cause of different swine flu in North America. 

From 1997 to 1998, several H3N2 strains appeared. These strains, including new strains that have evolved from the recombination of viral genes in humans, pigs, and birds, have become the main cause of swine flu in North America. The genetic recombination of H1N1 and H3N2 produced H1N2.

In 1999, in Canada, an H4N6 strain was cross-recombined between poultry and pigs, but was controlled on a farm.

H1N1 swine flu is one of the descendants of the Spanish flu that caused the outbreak from 1918 to 1919. 

In 1918, the offspring of the virus circulated in pigs, and they circulated among humans throughout the twentieth century, causing common seasonal influenza. However, it is not common to pass directly from pigs to humans. 

Since 2002, there have only been 12 cases in the United States. Nonetheless, after these strains disappear among humans, the influenza virus that remains in the pigs can make the pigs their depots and infect humans again in the future when human immunity is weakened.

The flu that broke out among humans in 1918

Influenza that was circulating among humans in 1918 was related to H1N1 and swine flu, and thus may be a human-to-animal infectious disease transmitted from pig-to-human or pig-to-pig. 

Although it is not certain from which direction the virus is transmitted, the available evidence suggests that pigs get sick from humans. For example, after the outbreak of influenza in humans in 1918, swine flu was first recognized as a new swine disease.

Human flu in the United States in 1976

On February 5, 1976, a recruit recruited at FortDix in the United States said he felt tired and powerless. He died the next day. Later, his four fellow soldiers were admitted to the hospital. Two weeks after his death, the health officer announced his death because of a new influenza strain.

The strain is a variation of the bird species H1N1 and is called H1N1. It was detected only from January 19th to February 9th, and did not spread outside FortDix. 
This new strain seems to be closely related to the 1918 flu. In addition, with increased surveillance, it was discovered that another strain of H3N2 was also spreading in the United States at the same time, which also caused disease and persisted until March of that year. 
The alert public health officer decided to take action against another outbreak, and urged President Ford to require all American citizens to be vaccinated.
The vaccination plan was hindered by delays and public relations issues. 

On October 1, 1976, the immunization injection operation began. By October 11, about 40 million people, or about 24% of the population, had received swine flu vaccine. On the same day, the three elders died shortly after receiving the flu vaccine.

A media announced that their death was related to the vaccine, although there is no definite evidence.

However, according to popular science writer Patrick DiJusto, it was too late when people learned that the death was not confirmed by the vaccine. He also said: 
"The government has long feared that the public will panic about the flu. They are afraid that the public will panic about the swine flu vaccine." This caused the prevention plan to be blocked. 

At the same time, there are some reports of Guillain-Barré syndrome symptoms. It is a disease that paralyzes muscles and nerves and affects some people who receive flu immunization.

This symptom is a kind of modern flu vaccine A rare reaction, only one out of every million vaccine injections. 

DiJusto wrote: "The public refuses to believe that the government has implemented a plan to slaughter the elderly and harm the health of young people."
As a result, by the end of 1976, there were only a total of Thirty-three percent of the population received vaccination. By December 6, the national influenza epidemic prevention plan had basically stopped.

In total, there were 500 cases of GBS. Twenty-five people died of pulmonary complications. According to Dr. P. Haber, this may be caused by the body's strong immune response to the 1976 vaccine. 

Other flu vaccines are not linked to GBS, although for some people, especially those with a history of GBS, doctors are cautioned to handle them with caution. Nonetheless, according to the observation of an immunization program participant, this vaccine killed more Americans than the flu.

In 1988, human-animal transmission of influenza

In September 1988, a swine flu virus killed a woman in Wisconsin and infected at least a few hundred people. Barbara Ann Wieners, 32, who was eight months pregnant, and her husband Ed visited the pigsty of the Farming and Animal Husbandry Fair in Walworth County, Wisconsin, and became sick after contracting pneumonia. He died eight days later.

The pathogen detected was a swine flu H1N1 virus. The doctor successfully helped her give birth to a healthy baby girl before her death. Her husband managed to overcome the symptoms and healed.

According to reports, similar flu diseases spread in the pig herds they visited; and 76% of the staff who participated in the pig exhibition between the ages of 9 and 19 were found to have SIV antibodies, but this group of people was not diagnosed seriously Condition. 

Another study proposed that one to three medical staff who had contact with the patient developed mild flu-like symptoms and was confirmed to have antibodies produced after swine flu infection. However, this incident did not cause a flu outbreak in the community.

Influenza among American swine herds in 1998

In 1998, swine flu was circulating among swine herds in four US provinces. Within a year, it spread throughout the US herd. Scientists found that the virus originated from the genetic recombination of two influenza strains in pigs and humans.
This outbreak confirmed that pigs can be a combination pot, where the genes of different strains can be recombined to form a new influenza virus.

Philippine Swine Flu

On July 27, 2007, when swine cholera spread to the backyard pig farms of Bragan and Pampanga provinces in the Philippines, the Philippine National Meat Inspection Bureau in Manila and Luzon, although there were no swine flu viruses, The region issued a "red warning sign" of pig cholera. 

On August 20, officials of the Ministry of Agriculture set out to investigate the swine flu that occurred in Nues Ecija and central Luzon. If there is no concurrent swine cholera, the swine flu mortality rate is less than 10%.

Influenza among humans in 2009

The 2009 influenza outbreak was caused by a new H1N1 influenza strain that has not been found in pigs before. 

In late April, when the first H1N1 virus was discovered in the United States, the WHO president announced the "urgent warning of an international public health threat" in accordance with the agency's new international health regulations. 

Following the outbreak of the flu, on May 2, 2009, the swine herd was found on a farm in Alberta, Canada, which was linked to the Mexican outbreak.

The pigs were suspected to have flu-like symptoms after being infected with this new virus by a worker who had just returned from Mexico. This may be the case, but it must be further confirmed by laboratory test results.

According to the original statement, the new strain appears to be a combination of at least four types of H1N1 influenza A viruses, including a strain of viruses that are prevalent in a group of people, a strain of viruses that are prevalent in a class of birds, and Virus strains prevalent in two types of pigs. 

The results of subsequent analyses suggested that it was simply the result of genetic recombination of two strains of pigs. 

Although the initial report identified the new strain as a swine flu strain (that is, a human-to-animal transmission strain that originated in pigs), it was later discovered that most of its genetic genes were derived from the first emergence of industrial farms in 1998 by the three strain of genetically recombined virus. 

Some countries have taken preventive measures to reduce the chance of disease spreading around the world.

Swine Flu in St. Petersburg in 2016

According to the Russian Satellite Network report, Tatiana Zasukhina, deputy chairman of the St. Petersburg City Health Committee in Russia, said on the 22nd that 15 people in St. Petersburg had died from complications after the flu, two of whom were pregnant.

The report said that on the 20th, there had been news that there were 4 death cases of "swine flu" in Leningrad Oblast.
Zushinna said: "We have confirmed that 15 people have died. Almost all of them have been confirmed to have died from a concurrent certificate of 'swine flu', especially pneumonia."
According to her, these deaths all suffer from other serious diseases, such as diabetes and obesity. 
She pointed out: "One of them is over 80 years old. There are two pregnant women in the death case."

Swine Flu Virus Fever H1N1

What are  the Clinical Symptoms of Swine Flu H1N1?

The incidence of the disease is high, with an incubation period of 2 to 7 days and a course of about 1 week. Sick pigs suddenly developed fever, lack of energy, loss of appetite or abolition at the beginning of the disease, often lying on their backs together, unwilling to move, difficulty breathing, intense coughing and mucus from the eyes and nose. 

If the treatment is not timely in the onset period, it is easy to complicated with bronchitis, pneumonia and pleurisy, etc., increasing the mortality of pigs.

Sick pigs have a temperature rise of up to 40 ° C to 41.5 ° C, depression, loss of appetite or no food, muscle pain, unwillingness to stand, viscous fluid from the eyes and nose, conjunctival congestion of the eye, difficulty breathing, gasping, coughing, etc. 

There is abdominal breathing, dog sitting posture and the sound of asthma in sick pigs can be heard at night. The joint pain of some sick pigs, especially the pigs with better fatness are more serious.

Post-mortem examination revealed that the larynx, trachea, and bronchus were filled with mucus containing air bubbles, congested and swollen mucosa, sometimes mixed with blood, enlarged interstitial lung, enlarged lymph nodes, hyperemia, splenomegaly, and catarrhal hemorrhagic inflammation of the gastrointestinal mucosa. The chest, abdominal cavity, and pericardial cavity accumulate fluid containing cellulose.

Epidemic characteristics Pigs of all ages, genders and breeds are susceptible to this virus. The epidemic of this disease has obvious seasonality, and the weather is prone to occur in late autumn, early spring and cold winter. 

The disease spreads rapidly, often endemic or pandemic. The disease has a high morbidity rate and a low mortality rate (4% -10%). Sick pigs and poisoned pigs are the source of swine flu infection, and the pigs are poisoned for 6-8 weeks after the disease is cured.

What are the Clinical Features of Swine Flu?

 The incubation period of this disease is very short, ranging from a few hours to several days. The average onset is 4 days. 

In the early stage of the disease, the body temperature of the sick pig suddenly increased to 40.3 - 41.5 , anorexia or loss of appetite, extreme weakness and even prolapse, often lying on the ground. 
There is shortness of breath, abdominal breathing, paroxysmal cough. 
Mucus flows from the eyes and nose, and nasal discharge is sometimes bloody. 

Sick pigs are huddled together, difficult to move, stiff and painful muscles, diaphragmatic spasms, and there are breathing convulsions, commonly known as hiccups.

If there is a secondary infection, the condition is aggravated and cellulose hemorrhagic pneumonia or enteritis occurs.

Sows are infected during pregnancy, and the piglets born are severely ill 2 to 5 days after delivery, and some die during lactation and before and after weaning.

H1N1 Swine Flu Virus and Other Viruses Comparison

What is the Pathology for H1N1 Swine Flu?

The pathological changes of swine flu are mainly in the respiratory organs. The mucous membranes of the nose, pharynx, larynx, trachea and bronchus are hyperemic and swollen, and the surface is covered with viscous liquid. 

The small bronchus and bronchioles are filled with foam-like exudate. The chest cavity and pericardial cavity accumulate a lot of slurry mixed with cellulose.

Lung lesions often occur on the back and base of the sharp lobes, heart lobes, interlobar lobes, and diaphragm, with a clear boundary with the surrounding tissues.

The color changes from red to purple, collapsed, solid, tough like leather and splenomegaly.

The neck lymph nodes, mediastinal lymph nodes, and bronchial lymph nodes are mostly swollen.

Syndrome identification Because influenza in pigs does not always appear in a typical form and is very similar to other respiratory diseases, clinical diagnosis can only be presumptive. In autumn or early winter, respiratory diseases in pigs can be suspected to be influenza.

Outbreaks of upper respiratory tract syndrome, including conjunctivitis, sneezing and coughing, and low mortality, can distinguish swine influenza from other upper respiratory tract diseases of swine, and should pay attention to swine asthma and this disease during differential diagnosis. The difference between the two is the most confusing.

What are the Prevention and Treatment Measures for Swine Flu?

There is no effective vaccine and special treatment for this disease. It is important to take good care and keep the pig house clean, dry, warm and free from wind attack. 
Supply sufficient clean drinking water, and during the first few days of recovery, feed should be restricted. Sick pigs should not be harassed or moved during the onset to reduce stress death.

The swine influenza is characterized by a sudden onset and rapid spread to the whole group. The main symptom is upper respiratory tract infection. It usually occurs in winter and spring and when the climate changes suddenly. The disease is also often secondary to H. parasuis.

What is the Diagnosis for Swine Flu?

Based on the epidemic history, morbidity, clinical symptoms, and pathological changes, the herd can be preliminarily diagnosed as influenza-associated swine parahaemophilus.


Two of the three viruses that infect humans also infect pigs. Among them, influenza A virus is commonly seen in pigs, while type C is rare, and there has been no report of influenza B virus infection in pigs. 

In influenza A and C viruses, there is a big difference between the disease types of pigs and humans, although due to genetic recombination, there have been gene series that cross between strains of pigs, poultry, and humans. Pass each other.

Influenza C Virus

Influenza C virus can infect both humans and swine, but not poultry. Cross-infection in humans and pigs has occurred. For example, influenza C has caused small-scale mild pediatric influenza in Japan and California. 

In view of the limits of the host (ie, foster population) of influenza C virus and the scarcity of its genetic variants, this influenza has not caused outbreaks in humans.

Influenza A

Swine flu has been confirmed to be caused by variants of H1N1, H1N2, H3N1, H3N2, and H2N3 subtypes of influenza A. The three most common viruses in the world are influenza A (H1N1, H3N2, and H1N2). 

Before 1988, the H1N1 subtype virus was prevalent among pigs in the United States. 

Since the end of August 1998, the H3N2 subtype virus has been extracted from pigs. 

As of 2004, the H3N2 virus extracted from American pigs and turkeys contains three types of strain genes of humans (HA, NA and PB1), pigs (NS, NP and M) and poultry (PB2 and PA) Triple cross combination.

What is the Precaution against Swine Flu Virus?

  • In order to avoid zoonotic infections, breeding managers and people who are in direct contact with live pigs should take effective protective measures and pay attention to personal hygiene.
  • Wash hands with soap or water frequently to avoid contact with affected pigs, and usually avoid exposure to flu-like symptoms (fever, cough) , Runny nose, etc.) or pneumonia and other respiratory patients especially after coughing or sneezing.
  • Avoid contact with pigs or places with pigs in front.
  • Avoid going to crowded places.
  • Cover your mouth and nose with tissues when coughing or sneezing and then throw paper towels in the trash. 
  • All pigs whose cause of death is unknown are burned and buried deeply before disinfection treatment.

 If a person is accidentally infected with the swine flu virus, they should immediately report to the higher health authorities, and the people who catch the disease should be observed for 7 days of medical isolation.

1. Lay bedding and change hay frequently, and disinfect the pig house regularly with 5% caustic soda.
2. Pay close attention to changes in the weather. Once the temperature drops, keep warm and keep warm in time.
3. Prevent susceptible pigs from contacting infected animals. When a person has influenza A, they should not be in contact with pigs.
4. The pigs were inoculated twice with swine flu adjuvant inactivated vaccine, and the immunization period can reach 8 months.

What are the Swine Flu Alert Levels?

Level 1 alert: In nature, influenza viruses are spread by animals, especially birds, but the virus has not yet spread among animals or transmitted to humans.
Level 2 alert: Influenza viruses from animals form spread to domestic or wild animals and begin to threaten humans.
Level 3 alert: The influenza virus carried by animals has infected a small number of people, but it is only a limited infection, and there is no sign of the possibility of widespread transmission. Bird flu is a three-level alert.
Level 4 vigilance: It is characterized by the infection of humans caused by the spread of animals that have been verified to humans and the outbreak at the community level. Its infection capacity is sufficient to have a significant impact on society. Any country that has such a situation must evaluate with WHO.
Level 5 alert: In at least two countries or regions, humans are spreading influenza viruses among themselves. This shows that the large-scale spread of the virus is imminent.
Level 6 alert: large-scale outbreaks of animal flu have begun worldwide

People infected with swine flu

The symptoms of swine flu infection in humans are similar to those of colds. Patients will develop fever, cough, fatigue, and loss of appetite. 

In terms of prevention, there is no need to get together to get a human flu vaccine at this stage, because the seasonal flu vaccine has no effect on preventing swine flu. 

The correct approach is to develop good personal hygiene habits, enough sleep, diligent exercise, reduce stress, and adequate nutrition. Wash hands frequently, especially after touching public goods, wash your hands before touching your eyes, nose and mouth. Sneeze When coughing, cover your mouth and nose with a tissue. Keep the room ventilated, etc.

Causes of transmission of the disease in the population Causes

Respiratory infectious diseases caused by swine flu virus, people will have flu-like symptoms after infection.


Similar to cold, fever, cough, fatigue, loss of appetite, etc.
The most obvious symptom of swine flu infection in humans is "the initial symptoms similar to ordinary flu, but the body temperature suddenly exceeds 39 degrees, the muscle soreness is significantly enhanced, accompanied by symptoms such as dizziness, headache, diarrhea, vomiting or some of them.


Fast spread: The human body does not have natural antibodies to new mutant viruses.

Mode of transmission

Sneezing, coughing and physical contact may cause the spread of the new swine flu virus among people.
The way of human infection with swine flu: It may be through contact with infected pigs or the environment infected with swine flu virus, or through contact with people infected with swine flu virus. 

It can be transmitted from people to pigs, and pigs can be transmitted from people to people, and can also be spread among people. 

Interpersonal transmission is mainly based on the cough and sneeze of infected persons. 
The symptoms of human swine flu infection are similar to those of ordinary human flu, including fever, cough, sore throat, body pain, headache, chills and fatigue, and some will also have diarrhea and vomiting. 

In severe cases, pneumonia and respiratory failure will occur. even death.

Susceptible crowd

The majority of people diagnosed with death from swine flu infection are between 25 and 45 years old, and the infected patients are mainly young adults, not the elderly and children.

What is the Incubation period of new swine flu virus?

The new swine flu virus may show symptoms after 7 days of incubation. The mortality rate of swine flu is 6.77%, which is higher than that of general flu. There are two main reasons for its high fatality rate: one is that the virus is fierce; the other is that the people did not pay much attention to new diseases at first, thinking it was a common cold, many people themselves Just take some medicine and miss the best 72-hour treatment period at the beginning of the disease.

What is the Prevention against Swine Flu H1N1?

Get enough sleep, diligently exercise, wash hands frequently, keep the room ventilated, etc., and develop good personal hygiene habits.

Personal protection measures include: 

  1. Avoid contact with respiratory symptoms such as flu-like symptoms (fever, cough, runny nose, etc.) or pneumonia.
  2. Pay attention to personal hygiene, wash hands often with soap and water, especially after coughing or sneezing; avoid contact with live pigs or Pig sites.
  3. Avoid crowded places; cover your nose and mouth with tissues when coughing or sneezing, and then throw the tissues in the trash. 
  4. If you have flu-like symptoms (fever, cough, runny nose, etc.) outside the country, you should seek medical treatment immediately (Wear a mask when going to a doctor) and explain to the local public health agency and inspection and quarantine department.

What is the Treatment of Swine Flu H1N1?

All influenza vaccines that humans have developed are ineffective against swine flu, but human infection with swine flu is preventable, controllable, and curable. Tamiflu is effective in the early stages of infection.

Nursing During Swine Flu

1. Isolate the patient from the rest of the family and keep a distance of at least 1 meter.
2. When taking care of patients, cover mouth and nose with masks and other coverings;
3. Regardless of whether the cover is purchased from a store or made at home, it should be discarded after each use or thoroughly cleaned by an appropriate method.
4. After each contact with the patient, wash hands thoroughly with soap. 
5. The space where the patient lives should maintain air circulation, and often open doors and windows to maintain ventilation.
6. If you have a case of H1N1 flu in your country, you should deal with family members who show flu symptoms according to the requirements of the national or local health department.

Author's Bio

Doctor Shawna Reason, Virologist
Dr. Shawna Reason
Name: Shawna Reason

Education: MBBS, MD

Occupation: Medical Doctor / Virologist 

Specialization: Medical Science, Micro Biology / Virology, Natural Treatment

Experience: 15 Years as a Medical Practitioner

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