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SWINE FLU M.PRASAD NAIDU MSc MEDICAL, Ph.D.
swine influenza viruses are usually introduced into a herd by an infected pig. • In a newly infected herd, up to 100% of the animals may become ill, but most animals recover within 3–7 days if there are no secondary bacterial infections or other complications.
In uncomplicated cases, the case fatality rate ranges from less than 1% to 4%. • Many infections in enzootically infected herds are subclinical; typical signs of influenza may occur in only 25% to 30% of the pigs.
Swine influenza, also called pig influenza, swine flu, hog flu and pig flu, is an infection caused by any one of several types of swine influenza viruses.
Swine influenza virus (SIV) or swine-origin influenza virus (S-OIV) is any strain of the influenza family of viruses that is endemic in pigs. As of 2009, the known SIV strains include influenza C and the subtypes of influenza A known as H1N1, H1N2, H2N1, H3N1, H3N2, and H2N3.
ELECTRON MICROSCOPE IMAGE OF THE REASSORTEDH1N1 INFLUENZA VIRUS PHOTOGRAPHED AT THE CDC INFLUENZA LABORATORY. THE VIRUSES ARE 80–120 NANOMETRES IN DIAMETER.
The influenza virion is roughly spherical. It is an enveloped virus; the outer layer is a lipid membrane which is taken from the host cell in which the virus multiplies. Inserted into the lipid membrane are ‘spikes’, which are proteins – actually glycoproteins, because they consist of protein linked to sugars – known as HA (hemagglutinin) and NA(neuraminidase).
These are the proteins that determine the subtype of influenza virus (A/H1N1, for example). TheHAand NA are important in the immune response against the virus; antibodies (proteins made to combat infection) against these spikes may protect against infection.
The NA protein is the target of the antiviral drugsRelenzaand Tamiflu. Also embedded in the lipid membrane is the M2 protein, which is the target of the antiviral adamantanesamantadine and rimantadine.
Swine influenza virus is common throughout pig populations worldwide. Transmission of the virus from pigs to humans is not common and does not always lead to human flu, often resulting only in the production of antibodies in the blood. If transmission does cause human flu, it is called zoonoticswine flu. People with regular exposure to pigs are at increased risk of swine flu infection.
Identification of influenza subtypes became possible, allowing accurate diagnosis of transmission to humans. Since then, only 50 such transmissions have been confirmed. These strains of swine flu rarely pass from human to human.
People who have swine flu can be contagious one day before they have any symptoms, and as many as 7 days after they get sick. Kids can be contagious for as long as 10 days.
Symptoms of zoonotic swine flu in humans are similar to those of influenza and of influenza-like illness in general, namely chills, fever, sore throat,musclepains, coughing,weakness, severe headache, and general discomfort.
H1N1 flu is also known as swine flu. It's called swine flu because in the past, the people who caught it had direct contact with pigs. • That changed several years ago, when a new virus emerged that spread among people who hadn't been near pigs.
Swine flu is contagious, and it spreads in the same way as the seasonal flu. • When people who have it cough or sneeze, they spray tiny drops of the virus into the air.
If you come in contact with these drops or touch a surface (such as a doorknob or sink) that an infected person has recently touched, you can catch H1N1 swine flu. • Despite the name, you can't catch swine flu from eating bacon, ham, or any other pork product.
The CDC recommends real time PCR as the method of choice for diagnosing H1N1. The oral or nasal fluid collection and RNA virus preserving filter paper card is commercially available.
This method allows a specific diagnosis of novel influenza (H1N1) as opposed to seasonal influenza. Near-patient point-of-care tests are in development.
Prevention of swine influenza has three components: prevention in swine, prevention of transmission to humans, and prevention of its spread among humans
Thermal imaging camera and screen, photographed in an airport terminal in Greece – thermal imaging can detect elevated body temperature, one of the signs of the virus H1N1 (swine influenza).
THERMAL SCANNING OF PASSENGERS ARRIVING AT SINGAPORE CHANGI AIRPORT
Vaccination (flu pandemic vaccine) Vaccines are available for different kinds of swine flu. The U.S. Food and Drug Administration (FDA) approved the new swine flu vaccine for use in the United States on September 15, 2009. Studies by the National Institutes of Health show a single dose creates enough antibodies to protect against the virus within about 10 days
In swine: As swine influenza is rarely fatal to pigs, little treatment beyond rest and supportive care is required. Instead, veterinary efforts are focused on preventing the spread of the virus throughout the farm, or to other farms.
Vaccination and animal management techniques are most important in these efforts. Antibiotics are also used to treat this disease, which although they have no effect against the influenza virus, do help prevent bacterial pneumonia and other secondary infections in influenza-weakened herds.
In humans: If a person becomes sick with swine flu, antiviral drugs can make the illness milder and make the patient feel better faster. They may also prevent serious flu complications.
For treatment, antiviral drugs work best if started soon after getting sick (within two days of symptoms). Beside antivirals, supportive care at home or in a hospital focuses on controlling fevers, relieving pain and maintaining fluid balance, as well as identifying and treating any secondary infections or other medical problems.
The U.S. Centers for Disease Control and Prevention recommends the use of oseltamivir(Tamiflu) or zanamivir(Relenza) for the treatment and/or prevention of infection with swine influenza viruses; however, the majority of people infected with the virus make a full recovery without requiring medical attention or antiviral drugs. The virus isolated in the 2009 outbreak have been found resistant toamantadine andrimantadine. I
n the U.S., on April 27, 2009, the FDA issued Emergency Use Authorizations to availableRelenza and Tamiflu antiviral drugs make to treat the swine influenza virus in cases for which they are currently unapproved. The agency issued these EUAs to allow treatment of patients younger than the current approval allows and to allow the widespread distribution of the drugs, including by volunteers.
