Swine Flu – Fatal Or Not?

Swine flu. An expression of terror develops on the face of the individual after hearing this. The whole world was affected by this viral disease. Many innocent people lost their lives because of this deadly disease. Swine flu is also called as swine influenza or hog flu, pig influenza or pig flu. Different types of viruses are responsible for causing swine flu. Swine influenza virus (SIV) or S-OIV (swine-origin influenza virus) is a strain of influenza family of viruses which is responsible for causing endemic in the pigs.

In 2009, the strains influenza C and the subtypes of influenza A which comprise H1N1, H1N2, H3N1, H3N2 and H2N3 were more prevalent.

The swine flu virus is very common among the pig population throughout the world. The transmission of swine flu virus from pigs to human is not very common and it may not always result in the development of human flu but simply develops antibodies in the blood in response to the virus. If human influenza is caused by the swine flu virus then it is called as a zoonotic swine flu. People working continuously are at a greater risk of getting infected with the swine flu virus and development of the disease. The properly cooked pork reduces the risk of infection if the meat of an infected pig is consumed. During the mid 20th century the classification of the subtypes of the influenza virus became possible. The strains of the swine flu are transmitted from human to human very rarely. The symptoms of swine flu in humans are similar to that of influenza and include chills, fever, sore throat, muscle pains, severe headache, coughing, weakness and general discomfort.

Categories of Influenza Virus

Of the three influenza viruses that are known to cause flu in humans, two are known to cause flu in the pigs, out of which influenza A is very common and influenza C is very rare. Influenza B has not been reported in the pigs till now. Both the strains of influenza virus A and C are completely distinct in the humans and in the pigs. Influenza virus C is responsible for causing flu in humans as well as pigs but it does not infect birds. Transmission of this virus have been reported in the past but because of its limited host range and lack of genetic diversity only small outbreaks are known from the countries like Japan and California. The following subtypes of influenza A are known to cause swine flu in humans as well as in pigs. These subtypes are H1N1, H1N2, H2N3, H3N1 and H3N2. Three strains have been reported to be the causative agents of flu in the pigs and these are H1N1, H1N2, and H3N2.

Historical Background

Swine flu was first proposed to be related to human flu in 1918 when the pigs developed symptoms similar to that occurring in the human beings when infected with the influenza virus. The identification of human influenza virus to be the causative agent of the swine flu was done in 1930. Since past 60 years H1N1 is responsible for causing the severe drastic outbreaks of swine flu in both humans and pigs. During the period of 1997 and 2002 another strain of influenza virus A was discovered to be responsible for spread of the disease severely and this was the strain H3N2. The major destructive strain of the influenza that was responsible for the pandemic in pigs during the 1918 was H1N1.

The descendants of the virus H1N1 also caused the outbreak of the swine flu during the 20th century in humans. The direct transmission of the virus from pigs to humans is very rare and only 12 cases have been reported since 2005 in the US. Swine flu has been reported as a zoonosis in humans but its distribution has been limited. It caused heavy loss to the pig industry resulting in heavy economic loss. A pandemic of swine flu in 1918 has occurred which was associated with the H1N1 virus and the flu was transmitted from both pigs to humans and from humans to pigs. In 1976 an outbreak occurred in the United States and at this time the strain which was responsible for the spread of the disease was H3N2. A vaccination programme was run to control the spread of the virus but it didn’t proved effective. An outbreak of swine flu also occurred in 1988 and 1998. People of Philippines were infected with the swine flu virus.

All of us are familiar with the outbreak of the swine flu in the year 2009 as the initial testing indicated that the genes of the virus were exactly similar to those of the influenza virus that caused swine flu in the North American swine. The virus that was responsible for causing this outbreak was H1N1. Margaret Chan the director general of World Health Organization declared swine flu as a matter of international concern as she found that about more than hundreds of people were found infected with this disease in April 2009. Swine flu became a major pandemic by the end of 2009 as it was responsible for the development of fear among the people. 17,700 people lost their lives because of swine flu. Many individuals also lost their lives because of fear too. Vaccines to cure swine flu are presently available.

Transmission of Disease

Transmission between pigs

Influenza is a very common disease in the pigs and about half of the breeding pigs are infected with this virus in the United States. The antibodies against this virus have been commonly found in the pigs of other countries. The disease is basically transmitted by the direct contact between the infected and the healthy individuals. The close contacts are often observed during the transport. Intensive farming is also one such factor for the spread of disease among the pigs. The virus is easily transferred through the touching of nose by the pigs and through the dried mucus. Air borne transmission is also possible as the aerosols are transferred easily by coughing and sneezing of pigs. The virus spreads very rapidly and can infect all the pigs of a herd within a few days. Wild boars may also serve as a source of infection to the pigs of a farm.

Transmission to Humans

Individuals involved in intensive poultry and swine are at more risk of being infected with the virus and are responsible for the zoonotic spread of the disease. Vaccination of such individuals is thus more important in order to prevent the outbreak of the disease. Meat processing workers as well as the veterinarians are also at the risk of getting infected with the virus but the chances are very small. Pigs are generally infected with the influenza virus which commonly infects three species including humans, birds and pigs. Pigs may act as hosts where the influenza virus may exchange its genes resulting in the production of more dangerous strains. The influenza virus H3N2 causes flu in the birds is endemic in China and easily produced new dangerous strains after getting entry in the pigs. H3N2 has evolved from the H2N2 virus by antigenic shift. In August 2004 scientists found that the pigs are infected with the H5N1 virus strain in China. This strain has emerged from the avian influenza virus.

Signs and Symptoms

In Pigs

The symptoms of influenza in pigs include fever, lethargy, sneezing, coughing, difficulty in breathing and decreased appetite. In some cases abortion may also take place. Mortality is low but the virus may lead to weight loss and poor growth resulting in heavy economic loss to the farmers. The infected pigs may lose about 12 pounds of body weight within a period of 3-4 weeks.

In Humans

The major symptoms of swine flu in human beings include runny nose, sore throat, fever, lethargy, lack of appetite, coughing, nausea, vomiting and diarrhea. Direct transmission of the swine flu virus from pigs to humans is occasionally possible. Only six deaths have been reported out of the 50 cases in the literature since 1958 for in which one case was that of a pregnant lady, one had leukemia and the other was suffering from Hodgkin disease. The outbreak of swine flu in 2009 was more intense because it was transmitted from humans to humans more in percentage rather than from pigs to humans. The death due to swine flu is mainly because of the respiratory failure. Other causes include pneumonia, high fever, dehydration, electrolyte imbalance and kidney failure. Children are at more risk of death than the elder persons. Diagnosis of swine flu can be done by RT-PCR for the isolation of H1N1. Other tests are under the process of development.

Prevention

In Pigs

Spread of the virus can be checked by facility management, herd management and timely vaccination of the pigs. Once infected with the influenza virus the pigs are also at the risk of being infected with other harmful pathogens. Control of the virus by vaccination is not completely safe as the virus is able to produce harmful strains. Presently bivalent vaccines are available for the control of the spread of the swine flu virus in the United States. These vaccines are not effective against the H3N2 strain. Facility management includes the use of disinfectants and ambient temperature to control the virus from growing. The virus cannot survive for more than two weeks outside the host except in cold and the disinfectants can easily inactivate the virus. Herd management includes avoidance of close contact between the infected pigs and the healthy pigs. The virus can remain alive in the carrier pigs up to 3 months and can result in the outbreak anytime. These carrier pigs may be responsible for the spread of the swine flu virus to the healthy pigs so such pigs must be quarantined.

In Humans

Swine may be infected easily with the avian and human influenza virus. The spread of the swine flu virus from pigs to humans is generally common among the farmers working in the pig farms. Although no strains of the swine flu virus are presently available for getting directly transferred from pigs to humans but the transfer may happen by chance. The workers working in the pig farms and the veterinarians are therefore encouraged to use masks while dealing with the infected individuals.

Vaccination may also be a preventive method. Use of gloves and avoidance of close contact with the infected individuals is also recommended. Influenza virus easily spreads from infected persons to normal persons by sneezing, coughing and touching anything containing the virus and touching with either nose or face. The virus is not transmitted by the consumption of pig products. The swine flu is contagious in humans up to 5 days and may remain contagious up to 10 days. Children are at a greater risk of getting infected. The diagnosis can be done sending a specimen collected during the first five days of infection.

The spread of the virus from humans to humans can be prevented by adopting standard methods of influenza control. These methods include frequently washing of the hands with soap and water or alcohol based sanitizers especially when present in the public places. Use of disinfectants especially the chlorine based solution and other strong disinfectants should be used for the cleaning of houses. Experts have suggested that the washing of the hands with soap and water can help in preventing the control of the virus and also always not touching the eyes and nose can also be helpful in preventing the spread of the swine flu virus. Social distancing is another measure for remaining safe from the virus.

Vaccination

Vaccines are available for different types of the swine flu. The US Food and Drug Administration (FDA) has approved a vaccine for the swine flu in the United States on 15September 2009. National Institutes of Health (NIH) has suggested that only a single dose is effective and it makes sufficient number of antibodies against the virus within a period of 10 days.

Treatment

In Swine

Swine influenza is rarely fatal to the pigs and little treatment and supportive care is required for preventing the virus from spreading. Vaccination and animal management techniques are the major steps that are supposed to be taken. Antibiotics may be used but they are not completely safe as they are ineffective against the virus and may be responsible for the appearance of symptoms of pneumonia and other secondary infections.

In Humans

If a person is suffering from swine flu then antiviral drugs may be taken and these help in recovering the patient. Apart from the antiviral drugs, supportive care at the hospitals and home can also help in recovering the patient faster. The FDA in 2009 has recommended the use of Tamiflu and Relenza for treating swine flu and they are completely safe.

We can conclude that swine flu is not a disease to be feared from but little attention, use of appropriate drugs and supportive care can be helpful in spread of the disease.

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