Swine Flu Overview
Swine Flu is called as Pig Influenza; various strains of swine flu virus are present endemically in the population of pigs. Influenza virus C and A are common and their sub strains H1N2, H2N1, H3N1, H3N2 and H2N3, virus are commonly found in the population of swine. Transmission of virus from pig to human is not common, if the human develops flu, probably due the production of antibodies in the blood the flu subsides. In the 20th Century due to development of sensitive equipments presence of subtype of viruses are easily detected ,which helps in making accurate diagnosis. For most people, the illness appears to be mild. For a minority of people, the virus can cause severe illness. In many of these cases, other factors contribute to the severity of the illness.
Classification of Swine Flu
Influenza A virus is common in pigs as compared to Influenza C virus. Influenza B cases has not been reported in the population of pig. Within the strains of Influenza A and influenza C which both are found in the Pig and Human are not largely distinct because of the re-assortment transfer of genetic material among strains of swine, avian and human occurs that results in the formation of new strain which is more virulent. Influenza C virus infects both human and pigs but not the birds. Cases have been reported in which transmission of genetic material between the Pig and the Human has occurred in the past.
Strains of Viruses
Various strains of Influenza A are found in pig population which exist as subtypes H1N1, H2N2, H2N3, H3N1, H3N2, the virulent form of subtype virus (H1N1, H1N2,H3N2, H7N9 are commune-able). Re-assortment of genetic material from Human (HN PB1), Swine (NS, NP and M) Avian (PB2and PA) results in formation of new sub type virus (H5N1) which has resulted in pandemic spread of swine flu globally for Which WHO has issued Pandemic alert 6.
Initiation with Avian Virus H5N1
Pigs are unusual as they can be infected with Influenza viruses might exchange genes which have produced a new dangerous strain. Avian virus H3N2 is endemic in pig .Emergence of new variant strain H3N2 evolved from H2N2by antigenic shift.
Mode of Transmission
- Transmission of Infection from pig to pig : influenza is quite common in pig, mostly the breeding pigs are more exposed .The main route of transmission is through direct contact between infected and uninfected animal, mostly infection is caused during transporting of pigs from one place to another ,Intense farming may also increase the risk of transmission, Air borne direct transmission may be due to aerosols /droplet infections produce by pig during coughing .It may also be transmitted through other animal.
- Transmission of Infection from pigs to human being : The people who work within the poultry and swine farm are at high risk of getting zoonotic infection with influenza virus, where as zoonotic infection with influenza virus is endemic in these animals .Possible re-assortment can occur. Preventive measure can be adapted to Vaccinate high risk workers against influenza virus. Surveillance for new influenza strain among the population may be an important public health measure. Professionals who are at high risk of influenza virus are veterinarians, and meat processing workers are at lower risk.
Signs and Symptoms of Swine Flu
In Pigs Influenza produces lethargy, sneezing, cough, and difficulty in breathing. Direct transmission of swine flu from pig to human is occasionally possible (called zoonotic flu) influenza like, illness include, fever, cough, sore throat, body aches and chills and fatigue. Outbreaks is indicative when increase number of patients reporting with symptoms of i.e. Diarrhoea and vomiting. Most common fatal cause of death is due respiratory disease. Complications are usually caused by the virus affecting the lungs. Infections such as pneumonia can develop. Most common fatal cause of death is due respiratory disease. Other Symptoms can be as follows:-
- Unusual tiredness
- Runny nose
- Sore throat
- Shortness of breath or cough
- Loss of appetite
- Aching muscles
- Diarrhea or vomiting
Diagnosis of Swine Flu
Diagnosis of confirmed by one more of the following tests: PCR, Elisa, Viral culture, four fold rise in pandemic (H1N1) 2009 virus specific neutralizing antibodies.
Treatment of Swine Flu
Consist of Antiviral drugs, the neuraminidase inhibitors are the drugs of choice
- Oseltamivir – As capsules or oral suspension (Tamiflu®)
- Zanamivir – For oral inhalation (Relenza®)
- Peramivir – A third neuraminidase inhibitor peramivir formulated for intravenous (IV) administration is an investigational product.
Strategy for control of Pandemic H1N1.
- Containment Phase: Almost over, so airport surveillance has limited effect.
- Outbreak management Phase: Through awareness (like social distancing), improved diagnosis, updated flu response centre, stock piling drugs, plan to manage social disturbances, monitor first case contacts
- Treatment Phase: Based on clinical diagnosis.
Risk Factors of Swine Flu
Persons with Cardiovascular disease, Respiratory disease i.e. Asthma etc, Diabetes mellitus, Cancer, Immunosuppressant illnesses, Hepatic and renal diseases, with poor socioeconomic status, pregnancy are at greater risk of disease.
Prevention of Swine Influenza
Prevention of influenza can be divided into three components; Prevention of influenza in swine’s, prevention of transmission from pigs to human and prevention of spread among humans.
- Prevention of Infection in Swine:
- Facility Management : methods of preventing the spread of influenza among swine include ,facility management , herd management and vaccination. Because much illness and death are associated with swine flu which is superimposed secondary by bacterial infection. Vaccination has become ineffective due to frequent reassorment /mutation in swine influenza virus. Using disinfectant in the facility and maintaining ambient temperature to control viruses in the environment ,they are unable to survive outside the living cell for more than two weeks expect in cold conditions in which the survival may rate may exceeds .They are readily inactivated with disinfectant.
- Herd Management: Adding Pig carrying influenza virus to the herds who have not been exposed to the virus .The virus survive in healthy carrier recovered from them between the outbreak of epidemic , carrier pigs are usually responsible for introduction of SIV into previously uninfected herd. The infection in the population of swine is controlled by the mechanism of community immunization.
- Prevention in spread of swine flu from Pig to human: The human can be infected with swine and avian flu strains of influenza ,the hosts where the antigens occurs new influenza strains is formed. Transmission can be infected with swine to human is believed to occurs mainly in some farms where farmers are in close contact with live pig .The individual are not directly affected from swine virus but farmers and veterinarians are encouraged to wear the mask. The individual dealing with sick pig are advice to get them self vaccination in order to limit the infection.
- Prevention in spread of infection from Human to Human
Influenza spread directly between human when infected people cough or sneeze, the other people breathe in virus or touch.
Certain Precautions may help in reduction of the disease:
- Wash hands frequently with soap and water, cover mouth & nose when coughing or sneezing, avoid touching your eyes, nose and mouth.
- people who are sick with an influenza-like illness (ILI) (fever plus at least cough or sore throat and possibly other symptoms like runny nose, body aches, headaches, chills, fatigue, vomiting and diarrhea) should stay at home.
- Keep away from others; avoid travel, for at least 24 hours after fever is gone. (Fever should be gone without the use of fever-reducing medicine). Avoid close contact (i.e. being within about 6 feet) with persons with ILI.
Indications of Vaccination
It is recommended that people in high-risk groups be vaccinated against swine flu. Persons at high risk for complication from the swine flu are as follows:-
- All children 6-59 months of age
- Person > 65 yr of age
- Adults and children >6 month of age with chronic heart or lung conditions, including asthma
- Adults and children >6 month of age who needed regular medical care or were in a hospital during the previous year because of a metabolic disease (like diabetes), chronic kidney disease, or immune system, including immune system problems caused by medicines or by infection with HIV/AIDS
- Children between the ages of 6 months to 18 yr of age who are on long term aspirin therapy because of the increased risk for Reye syndrome. Women who will be pregnant during the influenza season, Persons 50-64 yr of age.
- Persons who can transmit flu to others: This includes all health care workers, household contacts and out of home caregivers of children 0-23 months of age, and close contact of persons > 65 yr of age.
Vaccination Available is as follows:-
- Pandemrix: (Monovalent Influenza A( H1N1 2009). Whom to administer: Healthy children aged over six months and below 10 years: A single dose of 0.25ml. Immuno -compromised children aged over six months and below 10 years: Two doses of 0.25ml given at least three weeks apart.
- Celvapan: (Monovalent Influenza A H1N1 2009): All children aged over six months and below 10 years: Two doses of 0.5ml given at least three weeks apart. All children aged 10 years and over or adults: Two doses of 0.5ml given at least three weeks apart Vaccine manufacturers are Sonafi Pasteur, Novartis, and Intranasal by MedImmune, LLC, CSL Limitedent