Swine Flu

Swine Flu Overview

Swine Flu Symptoms

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

Swine Flu Cycle
Swine Flu Cycle

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

  1. 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.
  2. 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
  • Headache
  • 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.

  1. Containment Phase: Almost over, so airport surveillance has limited effect.
  2. 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
  3. 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.

  1. 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.
  1.  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
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