Swine Flu

Swine influenza virus ( referredto as SIV ) refers to influenza cases that are caused by Orthomyxovirusesendemic to pig populations. SIV strains isolated to date have been classifiedeither as Influenzavirus C or one of the various subtypes of the genusInfluenzavirus A. Swine influenza is known to be caused by influenza A subtypesH1N1, H1N2, H3N1, H3N2, and H2N3. 

Swineflu can to infected human and is found typically in people who have been incontact with pigs. The symptoms and transmission of the swine flu from human tohuman is much like seasonal flu, commonly fever, lethargy, lack of appetite andcoughing. Some people with swine flu also have reported runny nose, sorethroat, nausea, vomiting and diarrhea. Swine influenza virus is can be spreadbetween humans through coughing or sneezing of infected people and touchingsomething with the virus on it and then touching their own nose or mouth.

Main symptoms of swine flu in humans, including :

• Systemic → fever
• Psychological → lethargy, lack of appetite
• Nasopharynx → runny nose, sore throat
• Respiratory → coughing
• Gastric → nausea, vomiting
• Intestinal → diarrhea

The swine flu in humans is most contagious during the firstfive days of the illness although some people, most commonly children, canremain contagious for up to ten days.

Diagnosis can be made by sending a specimen, collectedduring the first five days, to the CDC for analysis. The Centers for DiseaseControl and Prevention (CDC) reports that the symptoms and transmission of theswine flu from human to human is much like seasonal flu, commonly fever,lethargy, lack of appetite and coughing. Some people with swine flu also havereported runny nose, sore throat, nausea, vomiting and diarrhea.

Swine influenza has become a greater problem in recentdecades as the evolution of the virus has resulted in inconsistent responses totraditional vaccines. Standard commercial swine flu vaccines are effective incontrolling the infection when the virus strains match enough to havesignificant cross-protection, and custom (autogenous) vaccines made from thespecific viruses isolated are created and used in the more difficult cases.

Present vaccination strategies for SIV control andprevention in swine farms, typically include the use of one of several bivalentSIV vaccines commercially available in the United States. Of the 97 recent H3N2 isolates examined, only 41 isolates had strong serologic cross-reactionswith antiserum to three commercial SIV vaccines. Since the protective abilityof influenza vaccines depends primarily on the closeness of the match betweenthe vaccine virus and the epidemic virus, the presence of nonreactive H3N2 SIVvariants suggests that current commercial vaccines might not effectivelyprotect pigs from infection with a majority of H3N2 viruses.

Thecurrent vaccine against the seasonal influenza strain H1N1 is thought unlikelyto provide protection. The director of CDC's NationalCenter for Immunization andRespiratory Diseases said that the United States'cases were found to be made up of genetic elements from four different fluviruses—North American swine influenza, North American avian influenza, humaninfluenza A virus subtype H1N1, and swine influenza virus typically found inAsia and Europe. On two cases, a completegenome sequence had been obtained. She said that the virus is resistant toamantadine and rimantadine, but susceptible to oseltamivir (Tamiflu) andzanamivir (Relenza).

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