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Influenza, which is known to some people flu transmitted from person to person due to transmission of the virus and it is contagious virus.Transmission peaks in winter is very high specially in the closed and crowded places are the places most likely to assist the transmission of the virus, such as schools, buses and shopping malls. There are three main types of flu virus these are: influenza virus A, influenza virus B and influenza virus C. In this assignment, am going to focus in influenza A.
Influenza A virus is belonge to the family of Orthomyxovirus, which is due to the genusOrthomyxovirus(Hui et al., 2010).
Influenza A virus is enveloped virion containing an outer membrane and having Hemagglutinin and Neuraminidase. It is found that Haemagglutin has 16 types and Neraminidas has 9 types. The envelope has eight segments, negatively single strand RNA genome, RNA polymerase ( PA, PB1, PB2), Nucleoprotein, Matrix protein (M1,M2), non-structural protein ( Richman et al., 2009). See figure 1
When the virus enters the body through the respiratory tract, the Haemagglutinin which is located on the surface of the virus recognize the target cell by the receptorsialyloligosaccharide which is contains N-acetyneuraminic (Sialicacid ) at its end. It is allowed the virus to inter to the plasma cell, due to the lower pH of the plasma , hydrogen ions inter to the virus from M2 channel. This stepstimulates the segments to release from the virus to the cytoplasm then to the nucleus. RNA are synthesis, new viral proteins are translated to cell membrane. New viral RNA ( capsid protein and matrix protein ) is transported to cell membrane where haemagglutitinin and neuraminidase molecules have been formed into cell membrane. New viroin are formed and released by budding(Perez et al., 2010).
Influenza A spreads more in winter. Influenza A virus is belonged to a family called Orthomyxoviridas, myxo has meaning of mucus and it is found in some animals in the respiratory tracts which is the primary form of influenza A infection. Ducks, chicken, pigs, whales and horse are animal that virus can developed and distributed between them, also it can transfer from these animals to the human in the close contact. Sneezing particles is one of the most important transmission factors of the viral infection. They were three possible way of viral transmission, the first one is aerosol transmission , the second is transmission by large droplets and the last is self-inoculation of the mucosa by contaminated hand. Aerosol transmission has the highest proportion(Tellier, 2009).
Sialic acid is the main component in haemagglutitinin, So after the viral inters to respiratory tract the carbon-2 molecules of the viral is bind to the carbon- 3 or carbon-6 on the receptor. Carbon-2 molecules can give to different types linked of bind, the first one is α-2, 3 which is found in ducks, and α-2, 6 found in humans. Both binds can be found in pigs. So pigs can receive viral infection of influenza A from ducks and humans (Perez ., 2010).
If a new strain was formed it is only change in the genetic material that means type A influenza cannot receive RNA from B and C strains which means the genetic change happen within the same strain. When any slightly change in the genetic of the RNA it will produce a change in the HN and NA which will by difficult to the antibody to recognize the viral. This mutation of the viral remains a life until the winter when influenza will spread as new strains from any of subtypes of H and N. Also it is founded that the replication of the influenza A virus is commonly happen in the upper part of the respiratory tract of the pigs but for H5N1 it did not replicate on it. This is happen due to the amino acid D256G found in the pigs which enhance the viral activity of the polymerase in the mammalian cells(Manzoor., et al 2009).
Pandemics infection of influenza A virus is obtained when the virus is transmitted from animal to human which they are not having any immunity response to the viral. Also this viral is transmitted from a human to human and cause a number of deaths.
Pandemics infection of influenza A virus which infected human and cause the number of deaths:
1 - 1918 (H1N1), which caused the Spanish flu and 20 to 100million died.
2 - 1957 (H2N2), which has caused the Asian influenza and 1 to 1.5 million died.
3 - 1968 (H3N2), flu, which has caused Hong Kong 1968 0.75 to 1 million died.
4 - 1976 (H1N1), swine flu episode
5 - 1977 (H1N1), Russian flu
6 - 1997 (H5N1),South-East Asia, died tens of millions.
7 - 2009 (H1N1), flu pandemic, 18,000.(WHO, 2009)
Fever is usually appears, it is between 37.8oc to 40oc, Aches and pain in muscle, back, arms and legs with headache and general feeling of sickness and loss of appetite, sometimes a dry cough, runny nose and sore throat. The viral will take about two days as incubation period. Then the symptom will remain for about five to seven days (WebMD,2011)
There are different methods for diagnosis of influenza A viral:
Rapid influenza antigen test: This is rapid test to diagnosis influenza and it can be done on observation room or doctored room with in 30 min the result obtained. Also it shows if its bacterial or viral infection and have a sensitivity to about 70%.
Direct fluorescent antibody stain (DFA): this method is used to differentia between influenza A and B.This method is more accurate then rapid test and the sample is taken from nasal secretions. But this method has disadvantage of it cannot recognize between influenza A( H1N1) and bird flu influenza.
Viral culture: This test has a benefited, it shows the types of viral infection in the respiratory tract, it usually take between 3 to 7 days.
Real-time polymerase chain reaction (RT-PCR ): This test is the most sensitive test from the above mention tests. It is analysis the genetic material of the viral. The sample where taken from the nasal secretions. The results are obtained from one day to several days. The test can analysis all kinds of influenza Aviral.
Influenza A antibody test: The sample is taken from the blood to check the body immune response(Merck,2011)
Prevention from influenza should be important things for every person. And each person has to prevent himself from influenza virus. Vaccination is the most important part of the prevention. Every year each person has to be vaccinated with the flu vaccine, for 2010- 2011 vaccine is a mixture of inactivated strains of influenza A H3N2 virus, influenza A virus and H1N1 virus.Normally vaccination has an efficiency between 67% to 92%. Usually, muscles injection is used for vaccination and there is a new live virus vaccine are available as nasal drops called flumist. However, a weak immune response and pregnant women cannot be vaccinated.
Anther factor to prevent influenza is to have hygienic life style, and avoid shopping center and crowded places during the spread of infection. Some people like to wear face mask during the influenza epidemic, it is a good idea specially the were some mask has effective about 99.999% to filter practical size more then 120nm, whereas influenza virus is between 80 to 120nm. Also there were hand antiseptic available in supermarket, it can be kept in the hand bag, it is very effective to the prevention from the virus(Weiss et al., 2007).
Treatment from influenza is started from the home, if the person feel that he has influenza ( headache, muscles pain, slightly fever) and they were no announcement from health organization of any epidemic infection of influenza he can have a bed rest, drink more fluids and use paracetamol or ibuprofen to relief the symptoms.
If the symptoms continue for 3 days the patient has to see doctor and have medication.The medication is either use antiviral directly or relief the symptoms until the immune system response to the infection.
The antiviral drugs can be divided in to two groups:
Neuraminidase inhibitors (e.g. Zanamivir and Oseltmivir)
M2 protien inhibitors ( e.g. Amantadine and Rimantadine)
Oseltamivir is classified as safe and very active to reduce the disease of influenza A virus specially during the epidemic of A(H1N1) in 2009. A lots of Oseltamivir were used widely in the world and the resistance to it increases up to more than 5% and this percentage will rise due to mutation in neuraminidase gene in A(H1N1) and also in H5N1(Wong et al., 2010).
Influenza A virus was been recognize form long time and until now every year it coming to each person more than one time. This virus has the ability to mutate. New strain will appear. The cooperation between the states should be increase under the international health regulation to prevent and control the public health risks that may spread between the countries. The responsibility to prevent and control the epidemic of influenza or any other infection has to be shared between the health sectors and non-health sectors.
In conclusion, everyone was get the influenza A virus every year as normal flu. And if the new strain is developed in ducks or pigs and transmission to humans it will be an epidemiologic decease a lot of peoples will die. In the modern life with the high speed of translation there were no bolder for the virus.