People who have close contact with pigs, including farmers and handlers of pigs, they run the risk of developing new types of influenza viruses. The virus can spread through droplets in the air or by touching a mucous membrane, and then infect it.

Features of the swine Flu

Swine influenza is an acute viral disease of the upper respiratory tract caused by influenza virus type A. It is an infectious disease and is transmitted mainly by direct contact between pigs and humans.

It is most common in fall or winter in North America and Europe, but can be found any time of year. It usually begins with one or two cases in a herd and spreads rapidly by direct pig-to-pig contact, thanks to nasal secretions and short-range aerosol transmission, possibly aided by the transfer of fomites from sick animals to pigs. healthy animals.

Swine influenza is a highly contagious and very virulent disease and in its classic form it is an explosive epizootic disease that affects the entire herd in a very short time, especially in those herds with continuous flows of pigs. It is endemic in pig populations worldwide and evidence of infection and antibodies is well documented, particularly in those regions where high levels of production are achieved using a continuous flow of pigs.

The virus belongs to the family of virus Orthomyxoviridae and contains a negative single-stranded RNA genome. Its surface is covered by glycoproteins hemagglutinin and neuraminidase, which are responsible for the attachment of the virus to cells and the release of infected particles into the host cell. Influenza A is divided into three main lineages or clades indicated by hemagglutinin and hemagglutinin-neuraminidase subtypes and these are subdivided into antigenic types that identify specific strains.

Swine influenza virus infection causes moderate to severe symptoms in pigs and a high mortality rate. Clinical signs of the disease include fever, cough, dyspnea, and sometimes diarrhea. The most serious complications of the disease are respiratory failure, a syndrome of multiple organ dysfunction that includes kidney and brain involvement, sepsis and death.

Transmission of swine flu to humans is rare, but has been documented several times since the late 1950s. Infection occurs mainly in people who have close and regular contact with pigs, such as farmers. Human infections with influenza A virus of swine origin are included in monthly communicable threats reports and annual zoonotic epidemiological surveillance reports. 

It has been shown that vaccination of pigs with vaccine strains oldest reduces the risk of swine flu in humans, however, the current vaccines against swine flu are not designed to protect against the pandemic H1N1 virus in 2009.

Detection

Swine influenza is a highly contagious infectious disease of the respiratory tract caused by the swine influenza A virus (SIV). The SIV genome is segmented and encodes multiple antigenic proteins, including hemagglutinin and neuraminidase. SIV infection leads to the production of a large number of viral particles that infect cells. 

Hemagglutinin is responsible for adherence to the host cell surface, while neuraminidase is essential for the release of viral particles from infected cells. SIVs are widespread enzootic agents in European pig herds and co-circulate with other enzootic and recombinant human influenza A viruses.

Influenza A infection of the respiratory tract is characterized by cough, fever, runny nose, and sneezing. The clinical picture varies from mild to severe and in advanced cases, it can cause pneumonia. Deaths are not uncommon due to pneumonia, ARDS, sepsis, and dehydration resulting from complications. The patient's underlying conditions and the duration of the disease influence the course of the disease, with the symptoms being more severe and the probability of death higher in patients under 5 years of age, adults over 60 years of age, and those who suffer from chronic respiratory diseases or obesity.

Transmission of the virus from pigs to humans is rare, but when it occurs it is usually short-lived and causes the production of antibodies in the blood of the infected person. When transmission results in a human case of swine flu, it is known as swine flu. zoonotic and it occurs mainly in people who have regular contact with pigs.

The VIS that cause the flu in humans are usually H1N1 virus, although the virus pandemic A(H1N1)pdm09 in 2009 was of swine origin. The influenza A virus of swine origin have never been detected in people before their introduction into the human population, with the exception of the pandemic influenza virus A(H1N1)pdm09 of swine origin.

Since the beginning of 2014, the trials of RT-qPCR for genes of hemagglutinin and hemagglutinin-neuraminidase of the swIAV have been included in the workflow of analytical routine used by the National Reference Laboratory of France to the swine flu, as part of a characterization more extensive swIAV. The use of kits of RT-qPCR-ready-to-use has allowed to evaluate and use the values Cq of hemagglutinin and of the gene for hemagglutinin of avian as a first step in the subtyping of swIAV.

Transmission of swine Influenza

The swine flu often appears as an outbreak, usually at the start of a period of cold weather, but it can occur at any time of the year. It spreads quickly within the herd by direct contact between animals, aerosolization (limited distance) and transfer of fomites. The infection is endemic in pigs in the entire world, as evidenced by the seroprevalence of antibodies and titers of circulating viruses.

Swine flu mainly affects the respiratory tract and is characterized by fever, cough and runny nose in the initial phase of the disease. It progresses to pneumonia, a pattern reminiscent of classic human influenza, with pronounced bronchointerstitial lesions of the lungs with marked cellular infiltration and necrosis of epithelial cells. These lesions cause atelectasis, emphysema, and interstitial pneumonia and may be associated with a bacterial infection high school.

The entry of the virus occurs through the nasopharynx and penetrates the epithelium of the nasal cavity and the large airways. The replication of the virus in the epithelium causes a degeneration of generalized epithelial cells and cell necrosis, which causes a thickening of the mucous membrane of the respiratory tract. The virus also infects the pneumocytes in alveolar type 2, which causes a decrease in the production of surfactant. This alters the phagocytosis of macrophages in the lung and results in the accumulation of exudates inflammatory drugs that block the airways and small cause atelectasias.

The clinical picture and pathology of the disease in pigs is similar to that observed in humans, and the severity of the disease is a reflection of the strain of virus involved. There is anecdotal evidence of human infection by swine influenza viruses, in particular strains grouped containing genes from swine, avian strains and some of the human.

The transmission of swine flu to people is not well understood, however, sporadically, human infections with swine flu viruses have occurred in people who have had close or frequent contact with pigs. This has mainly occurred in people who work or live near pig farms. 

These cases are reported in zoonotic influenza epidemiological reports. In most cases, infection is a “dead end” and does not lead to new transmissions within the human population. Swine influenza virus infections, unlike other types of flu, are generally considered low risk to public health.

Prevention

Swine influenza is a zoonotic respiratory disease of pigs caused by influenza type A viruses. The virus is transmitted from pig to pig by direct contact, by being carried by something that has been touched by an infected animal, and also by inhalation of respiratory excretions. Swine flu is present in pigs of all ages worldwide and is most common in fattening animals in autumn and winter, although outbreaks can occur throughout the year and also in younger pigs of breeding age. 

It is not unusual to have infection simultaneously in pigs with 2 or more different strains of the influenza virus, and this can result in the recombination of the genetic material and the development of new influenza viruses.

Swine flu is a highly contagious respiratory disease and spreads rapidly in pig herds. Pigs with this virus develop fever, oculonasal discharge, prostration and weakness followed by paroxysmal cough. Symptoms are usually mild, as is the case with other swine diseases such as the PRRS, but, in some cases they can be serious and death rarely occurs. Vaccinating pigs against influenza helps control the disease.

Humans can contract swine flu through direct contact with infected pigs or contaminated food, water, or bedding. In humans it can cause fever, headache, runny nose, cough and vomiting. Humans do not usually die from swine flu, but they can become seriously ill and hospitalized.

The prevention of swine flu in people are focused on avoiding close contact with pigs and other animals, in addition, people should wash their hands frequently with soap and use hand sanitizers alcohol-based hand rub, especially after going to the bathroom or use shared equipment such as phones or latches. 

If a person suspects they have swine flu, they should see a doctor immediately. Antiviral medications such as oseltamivir (Tamiflu) or zanamivir (Relenza) can shorten the duration of the illness and reduce symptoms. It is also recommended that people get an annual flu vaccine to help protect against H1N1 and other flu viruses (this can be done at many local clinics and pharmacies). The vaccine is available as an injection and as a nasal spray. Both the injectable and the nasal spray are effective in protecting against swine flu.