2 Etiology influenza virus is an orthomyxovirus. This type of virus is divided into three groups; type A, type B or type C.Type A viruses are further divided into subtypes based on their hemaglutinin (H) and neuraminidases (N).
3 Influenza virus structure … A ssRNA enveloped viruswith 8 pieces (genes)of RNA… With 2 surface glycoproteinSpikes – H and N… And hemispheric clades of 15 H genes, 9 N genesE.g. “H5N1” Bird flu ….U.S. orders $200 million in H5N1 bird flu vaccine
4 Influenza changes 1. by antigenic drift of HA and NA, 2 Influenza changes 1. by antigenic drift of HA and NA, 2. by cleavage of the HA, 3. by HA changing to bind to different receptors and, further by “shift” through Genetic Reassortment
5 Swine Flu and VirusSwine Influenza (swine flu) is a respiratory disease of pigs caused by type A influenza virus that regularly causes outbreaks of influenza in pigs. Swine flu viruses cause high levels of illness and low death rates in pigs. Swine influenza viruses may circulate among swine throughout the year, but most outbreaks occur during the late fall and winter months similar to outbreaks in humans. The classical swine flu virus (an influenza type A H1N1 virus) was first isolated from a pig in 1930.
6 Swine Flu differs from Human Flu At this time, there are four main influenza type A virus subtypes that have been isolated in pigs: H1N1, H1N2, H3N2, and H3N1. However, most of the recently isolated influenza viruses from pigs have been H1N1 viruses. The H1N1 swine flu viruses are antigenically very different from human H1N1 viruses and, therefore, vaccines for human seasonal flu would not provide protection from H1N1 swine flu viruses
7 Why Pigs? 1-Ducks and pigs are raised by humans in close proximity. 2-Pig cells have virus receptors (virus binding capability) for both avian and mammalian influenza strains
8 Influenza Reassortment NewStrainDomesticDuck or ChickenNew Reassortmentof Influenza virusgene segments arisesin a pigMixed infection of a pig
9 Many H5N1-infected chickens Few H5N1-infected humans No human-to-human transmission
10 Many H5N1-infected chickens Reassort genesMany H5N1-infected humansModerately efficient human-to-human
11 Elements of a pandemic: Many H5N1-infected humans Good human-to-human transmission
12 Stable Species Jumps or “Evolutionary Transmissions”
13 Stable Species Jumps or “Evolutionary Transmissions”
15 Summary Year U.S. Deaths % pop Global deaths % global pop 1918 660,000 0.6020-40 M195770,0000.04196834,0000.02Next: low estimate102,0862.0 M0.03Next: high estimate*315,2000.117.4 M0.12
16 Transmission:Swine flu is contagious and is spreading from human to human. However, at this time, it is not known how easily the virus spreads between people.Swine flu is thought to be spread from person to person in the same way seasonal influenza and other common respiratory infections spread.Being in close contact (eg. within a metre) with an infected person while they are talking, coughing or sneezing putsyou at risk of becoming infected. Virus-containing droplets can land on the surfaces of the mouth, nose and throat of people close by. The virus may also be spread through contact with infectious respiratory secretions on the hands of an infected person or other objects and surfaces.
17 How long can viruses live outside the body? We know that some viruses and bacteria can live 2 hours or longer on surfaces like cafeteria tables, doorknobs, and desks. Frequent hand washing will help you reduce the chance of getting contamination from these common surfaces.
18 Infectious PeriodPeople with swine influenza virus infection should be considered potentially contagious as long as they are symptomatic and possibly for up to 7 days following illness onset. Children, especially younger children, might potentially be contagious for longer periods.
19 How Swine Flu presents in Humans The symptoms of swine flu in people are expected to be similar to the symptoms of regular human seasonal influenza and include fever, lethargy, lack of appetite and coughing. Some people with swine flu also have reported runny nose, sore throat, nausea, vomiting and diarrhea
20 Seek emergency medical care. IF - in Children In children emergency warning signs that need urgent medical attention include:Fast breathing or trouble breathing Bluish skin color.Not drinking enough fluidsNot waking up or not interactingBeing so irritable that the child does not want to be heldFlu-like symptoms improve but then return with fever and worse coughFever with a rash
21 DiagnosisTo diagnose swine influenza A infection, a respiratory specimen would generally need to be collected within the first 4 to 5 days of illness (when an infected person is most likely to be shedding virus). However, some persons, especially children, may shed virus for 10 days or longer. Identification as a swine flu influenza A virus
22 No Vaccines to Humans But available to PIGS Vaccines are available to be given to pigs to prevent swine influenza. There is no vaccine to protect humans from swine flu. The seasonal influenza vaccine will likely help provide partial protection against swine H3N2, but not swine H1N1 viruses.
23 Drugs which are effective in Swine Flu There are four different antiviral drugs that are licensed for use in the US for the treatment of influenza: Amantidine, rimantadine, oseltamivir and zanamivir. While most swine influenza viruses have been susceptible to all four drugs