What is Influenza?
Influenza is an accute respiratory tract infection caused by Influenza Virus, of which there are 3 types – A,B and C. All known Pandemics were caused by influenza A strains. The Disease is characterized by sudden onset of chills, malaise, fever, muscular pains and cough. It is truly an international disease which affects millions of people every year. Its Behaviour is Unpredictable. It may occur in several forms. It may smoulder in a community without clinical recognition, being manifest only by serological surveys. It may occur in pandemics every 10-40 years due to major antigenic changes, as occured in 1918 (Spanish) and 1968 (Hong kong). It is Mainly spread from person to person by droplet infection created by coughing and talking.
Types of Influenza
At Present, Three types of Influenza are circulating in the world : A, B, And C. These three viruses are antigenically distinct. There is no cross immunity between them. Of importance are the influenza A and B viruses which are responsible for epidemics of disease throughout the world.
Influenza A Virus has two distinct types :
1) The Haemagglutinin (H)
2) The Neuraminidae Antigens (N)
The H Antigen initiates infection following attachment of the Virus to susceptible cells. The N Antigen is responsible for release of the Virus from infected cells. The Influenza A Virus is unique among the viruses because it is frequently subject to antigenic variation, both major and minor. When there is a sudden complete change or major change, it is called a shift, and when the antigenic change is gradual over the time, it is called a drift. Health is Necessary for a Healthy Well Being.
Factors of Influenza
1) AGE AND SEX : This Infection affects all ages and both sexes. In general, the attack rate is lower among adults. Children constitute and important link in the transmission chain. The highiest mortality rate during an epidemic occurs among certain high-risk groups in the population such as old people, children under 18 months, and persons with diabetes or chronic heart diseases.
2) HUMAN MOBILITY
3) IMMUNITY : Immunity to Influenza is subtype specific Antibodies against HA and NA are important in immunity to influenza. The logical antibody is probably important in preventing infection.
4) SEASON : The seasonal incidence is striking, epidemics usually occuring in winter months in the Northern Hemisphere and in the Winter and in the winter or rainy season in the Southern Hemisphere.
How to Prevent from Influenza?
All attempts to control influenza epidemics have so far met with little success and the prospects of achieving control remain poor, Good Ventilation of Public buildings, the Avoidance of crowded places during epidemics, encouraging sufferers to cover their faces with a handkerchief when coughing and sneezing, and to stay at home at the first sign of influenza are all sensible precautions. The Vaccine is not recommended to control spread spread in the General Population.
Immunization, in theory offers the best prospect of controlling influenza at the present times. In view of the changing antigenic characteristics of the virus, new vaccines are constantly required, and they should contain the H and N components of the prevalent strain or strains to keep vaccines up to date. The WHO makes recommendations every year as to what strains should be included in the vaccine. A number of field trials have shown that vaccines so constituted are highly effective (70-90%). To be effective the vaccine must be administrated at least two weeks before the onset of an epidemic, or preferably 2 to 3 months before it is expected.
HIV persons can be safely vaccinated and concerns about replication of HIV virus by the immunogen appear to be exaggerated and may be less severe than the increase in HIV viral load associated with a full influenza infection. Vaccination is less effective when CD4 counts are less than 100/mcL.
Prevention of exposure t0 avian strains about includes hygienic practises during handling of poultry products, including handwashing and prevention of cross-contamination as well as through cooking to more than 70 degree calcius of poultry products.
Treatments / Vaccines for Influenza
1) Killed Vaccines : Most influenza vaccination programmes make use of inactivated vaccines. The recommended vaccine strains for vaccine production are grown in the allatonic cavity of developing chick embryos, harvested, purified, killed by formalin or beta-propiolactone, and standardized according to the haemagglutinin content. The vaccine is conventionally formulated in aqueous or saline suspension. Treatment is possible but the killed vaccine can produce fever, local inflammation at the site of injection, and very rarely Guillain-Barre Syndrome.
2) Live-Attenuated Vaccines : A Trivalent, live-attenuated vaccine administrated as a single dose intranasal spray is as effective as inactivated vaccine in preventing the disease. It is approved for use in otherwise healthy individuals between age of 2 years and 49 years.
3) Antivirual Drugs : Because of the limitation in the efficacy of influenza vaccines antiviral drugs have been tried for the prophylaxis and therapy of seasonal influenza infections. If this is contraindicated, patients should be given rimantadine. In an outbreak associated with influenza B, either oseltamivir or zanamivir can be used for prophylaxis. Thank You!
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