Influenza or flu as normally known is one of the emerging infective diseases. It is a contagious respiratory disease caused by grippe virus which is an RNA virus. New strains of the grippe virus are go oning to look giving rise to annually epidemics. Some of the all of a sudden looking strains are wholly new to human ‘s immune system and that is the cause of the pandemics which may sometimes be black. ( Robert,1998, Online ) . The most serious human pandemics are caused by grippe A virus. It causes the most deadly infection in worlds.
The Influenza Virus
Influenza is caused by an RNA virus from the household Orthomyxoviridae. This household includes 4 genera: grippe A, B, C and Thogovirruses ( Greenwood, 2002 ) . We are traveling to speak about the genus influenza A, as this is the 1 that causes pandemics in add-on to epidemics. This genus comprises of one coinage, Influenza A virus. This specie infects many host species including birds and mammals like swine, Equus caballuss, Canis familiariss, cats and worlds.
Figure construction of influenza virus virion. Adopted from/www.wvdhhr.org/The virion of the grippe A may be either spherical measurement 80-120 nanometer in diameter or filiform but the spherical form is more common. The genom is found in the Centre of the virion. It consists of 8 sections of individual stranded RNA. All these are surrounded by an M1 protein mirid bug which is so enveloped by a lipid bed derived from the host cell. There are three projections on the surface of the envelope. From the M2 protein undertakings some Fe channels leting alterations in the endosome. The other two spikes undertaking from the envelope itself and these are haemagglutinin and neuraminidase. These are type finding antigens used to stipulate different strains of grippe A virus. There are 16 different H antigens get downing from H1 to H16, and 9 different N antigens ( N1- N9 ) . Different combinations of H and N antigen give the different strain names like H3N2, H1N1 and H1N2. There are other factors which are of import in the full terminology. These include grippe group, the topographic point and twelvemonth foremost isolated and eventually the strain. For illustration, A/Phillipines/82/H3N2. ( Mims,2004, p227 ) influenza_projections.jpg
Like all other grippe viruses, this virus undergoes familial alterations while distributing from host coinage to another. These are known as ;
Antigenic impetus ; this is slow series of mutants go oning over a long period of clip taking to gradual alteration of the virus. These mutants take topographic point in the antigenic binding site ensuing in a new strain of virus that ca n’t be inhibited by the antibody produced against the old strain. This is a common characteristic between grippe A and grippe B. ( Richman et al.,2002, p.899 ) .
Antigenic displacement ; this characteristic is the 1 that makes Influenza A virus unique in the manner it causes sudden pandemics. This is a sudden major alteration in the H and N antigens. It occurs when two different strains infect the same cell so a recombination between the strains take topographic point. The ensuing strain is wholly new to the immune system and may take to pandemic spread. ( Mims et al, 2004, p227 )
Influenza virus is transmitted by direct contact with an septic individual, touching objects contaminated by the virus or by inhaling aerosols transporting the virus.
Figure universe map with instances of H1N1. adopted from gamapserver.who.int/mapLibrary/app/searchResults.aspxBecause of the complex familial alterations that occur in grippe, epidemics happen every twelvemonth particularly in the winter and fall. The badness and spread of the epidemic differ harmonizing to the subtype doing it. In a twelvemonth three to five million people develop the infection and 2500000- 500000 deceases are recorded worldwide ( WHO,2010 ) Harmonizing to the Canters of Disease Control and bar, in the United States of America entirely an norm of 5-20 % of the population gets flu each twelvemonth. 200000 and more people get hospitalized because of fluke and its complications.36000 people die for the same ground. ( CDC,2010 ) .Influenza causes pandemics besides. One of the most serious pandemics of grippe A virus was the Spanish grippe that take topographic point in the old ages 1918 and 1918. At that clip 40-50 million people died to from the disease worldwide. This was caused by subtype H1N1. Another major pandemic was the Asiatic grippe caused by H2N2 between the old ages 1954 and 1958. It caused deceases of about 69800 worldwide. ( Green,2006 ) . The last 1 is the 2009 grippe or what was named as swine grippe. This was first recognized in March 2009 in Mexico and the new strain of H1N1 caused the pandemic was foremost identified in April the same twelvemonth. Harmonizing to the World Health Organization hebdomadal update study published at 11th of December 2009, more than 208 states around the word reported research lab confirmed instances and the entire figure of the deceases were 9596 worldwide. The last study from the WHO at 3rd of March 2010 showed the map in figure2. The map well shows that this pandemic affected about the whole universe and no less than one decease was reported from most of the countries.GlobalSubnationalMasterGradcolour_20100103_weekly.png
This virus differs in the manner it attaches to the host cell harmonizing to the strain and the host that it infects. The human grippe A virus recognizes receptors that contain sialic acid which are linked to penultimate sugar with an alpha2,6 linkage. In avian grippe strains the receptors contain alpha 2,3 linkage but in hogs both are present. The virus attaches to the cell receptors by its haemagglutinin and by the procedure of endocytosis it enters the cell. Once inside the cell, the alteration in the environing pH leads to the merger of the haemagglutinin with the cell membrane. After that the virus releases its RNA and RNP to the cytol of the infected cell so they are transported to the cell nucleus. In the karyon, written text of the viral RNA mulecules takes topographic point and messenger RNA molecules are produced. New viral protein and viral RNA are so produced and these are so transported to the cell membrane and joined by H and N glycoprotein. At this phase, new viral atoms are assembled and so released out of the cell by budding with the aid of neuraminidase. Then these new viral atoms are ready to infect new cells. ( Greenwood, 2002 ) flu2life ( 1 ) .gif
Figure. Influenza viral reproduction. Adopted from hypertext transfer protocol: //web.uct.ac.za
Transmission & A ; Incubation Period
This virus is easy transmitted from individual to individual through the droplets emitted by an septic individual when sneeze or coughing. Another individual in the environing country will inhale the septic droplet. The fact that this individual will acquire the infection depends on many things including the size of the droplet or aerosol he inhaled. Small sized droplets most of the times precipitate in the little air passages and do n’t make the air sac. ( influenza study, 2009 ) . Close contact is required as this virus will non stay suspended in air. Transmission can besides be by direct tegument to clamber contact or by touching contaminated surfaces. This is possible because this virus can last in the environment for a long clip particularly in cold conditionss. The incubation period for this virus ranges from 2 yearss up to 5 yearss and the patient can still be able to go through the virus to other people during these yearss. Childs are more infective and can distribute the virus for a longer period of clip. ( Fabrice Carrat, et all,2006 ) huge_23_116043.jpg
Entrance of the viral atoms to the host ; this starts when a individual inhales the contaminated droplet, it enters its respiratory piece of land, and the virus starts to move on the columnar epithelial cells at that place. This will take topographic point unless the viral atom passes all the defense mechanism mechanisms of the host. They include the mucous secretion bed, the mucous secretion bring forthing secretory organs and the cilia that cover the piece of land.
Adhering to the host cells ; the binding will take topographic point between the receptors on the host cell and the haemagglutinin biding site
Viral reproduction ; one time the virus finds the right receptor on the host cell it enters the cell and starts to retroflex and do transcripts of it. The new viruses so do the same with the neighboring cells.
Hypersensitivity ; in the procedure of reproduction and when new grippe viruses are produced the septic cells get ruptured. When the lyses take topographic point in the epithelial of the upper respiratory system, it causes the mucosal cells to go vacuolated and conceited taking to the hypersensitivity of the respiratory piece of land cells and production of more mucous secretion. This is the cause of the common symptoms of fluid olfactory organ, rhinal congestion and cough. ( Wilschut, et all, 2006,
Figure immune rsponse after influenza infection. adopted from www.influenzareport.com After the iterance of the virus to the organic structure, two types of immune response take topographic point. One is cellular immune response and the other is the more specific humeral immune response.image27.jpg
Cellular immune response ; at the site of vaccination macrophages engulf the viral atom and after that represent some of the antigens of the virus to lymph cells. Cytotoxic T lymph cells are one of the cells that recognize the viral anrigens presented by the dendritic cells so they are activated. When cytotoxic T lymph cells are activated, they lead to the procedure of violent death of the septic cells. T assistant lymphocytes besides recognize the viral antigens on the surface of the dendritic cells and acquire activated. The activation of these cells lead to the production of cytokines which so help in humoral immune response.
Humoral immune response ; B lymph cells will besides place the viral antigens straight from the site of vaccination. Then with the aid of the T lymph cells and the cytokines produced from cellular immune response B cells will be activated hence green goods specific antibodies against the invading grippe virus.
All these processs will work together to halt the virus from distributing and get down the healing procedure.
Clinical manifestation ;
Normally influenza A causes upper or lower respiratory infections but sometimes may do other complications due to secondary infections. The complications may be really serious in some group of people like the aged, kids, and people with other diseases. ( Richman.et, al.2002, p.905 ) . it is thought that the ground behind the addition figure of deceases from bosom disease is due to the fact that grippe is more at those times. The most common complication of grippe is Pneumonia. This may be caused by the virus itself or a secondary bacterial infection due to the weekend immune system of the patient. The viral pneumonia occurs normally after 5 yearss of infection. Some other less common complications include otitis media, toxic daze syndrome, redness of the bosom musculus and paroxysm ensuing from febrility. ( Richman.et, al.2002, p.905 ) . The normal symptoms of grippe A infection is ever confused with common colds particularly at the early phases. Influenza infection causes a sudden unwellness with systemic symptoms like ;
Fever – Chills – Headache – Myalgia – Anorexia
The best samples for proving Influenza A virus are, nasopharyngeal swab, rhinal swab and rhinal wash or aspiration and the pick depends on the method of proving to be used. Sample must be collected within the first 4 yearss of unwellness. ( CDC, 10 ) Some of the trials done to observe the disease include ;
Viral civilization ; consequences from this trial will be ready within 3-10 yearss
Immunofluorescence Antibody Staining. This is done to place the virus on tissue civilization or can besides be performed straight on the sample.
Serology trial to observe the particular strain doing an eruption. This is utile in epidemiology and vaccinum production but this method may be non really sensitive. First, compliment arrested development trial are normally done to observe that the infection is A, B or C infection. Then other methods like neutralisation checks or strain specific compliment arrested development trials are used to place the strain. ( Greenwood, et all, 2004, p 472 )
Rearward transcriptase-PCR to observe Influenza RNA. This method possibly really utile but is non available in most diagnostic research labs.
Figure Influenza A antigen rapid trial kit. Adopted from quicking.en.alibaba.comRapid diagnostic trial for grippe. These are commercially available trial kits used to observe the consequences within few proceedingss. They are immunoassays observing the viral antigen. The type of specimens used and the clip needed to acquire the consequences depend on the kit used. These trial are utile in topographic points with allot people like infirmaries where consequences are needed rapidly to take actions like isolation of the patient from other patients.Influenza_A_Antigen_Rapid_Test_Kit.jpg
Adamantanes ( amantadine and remantadine ) ; these unwritten drugs are widely used as intervention and contraceptive agent against Influenza A virus. These drugs act on the viral envelop by barricading the ion channel and hence prevent the pH alteration. Subsequently, the viral atom will non be uncoated after the endocytosis to the cell. This drug is purely used to handle Influenza A non B or C but it can besides demo resentence against some strains of Angstrom
Neuraminidase Inhibitors ; these drugs inhibit the action of neuraminidase and therefore forestall the virus from acquiring out of the cell by budding after reproduction. They can cut down the continuance of the disease by 1-3 yearss if given in the early yearss of the oncoming of disease. . ( Greenwood, et all, 2004, p 474 ) There are two signifiers of these drugs ;
Zanamivir. This is given as dry pulverization to be inhaled for 5 yearss.
Oseltamivir. This is what is known as Tamiflu and its an unwritten drug given twice daily for 5-7 yearss.
These drugs were proved to be used for intervention and as prophylaxis but some mutated strains showed opposition to them. For illustration, it was reported in the Pandemic H1N1 briefing of the WHO published on December 2009 that two bunchs of patients infected with Oseltamivir immune H1N1 were found. One was from Wales UK and the other from North Carolina in the US. Both bunchs were from hospital words with immune-compromised patients. ( WHO,2010 )
Prevention and control
Influenza Vaccines. The seasonal vaccinum is an one-year vaccinum that it produced from a combination of two grippe ( H1N1 and H3N2 ) viruses and one grippe B. The strains to be used each twelvemonth are recommended by WHO Global Influenza Surveillance Centre and 250 million doses of grippe are produced yearly. ( WHO,2010 ) The vaccinum is made in two signifiers ; FLUMIST.jpg
Flu Shot ; this is made by utilizing killed signifier of the three virus strains and given as injections.
Figure ; Flu nasal spray. Adopted from www.stuttgart.army.milNasal spray ; in this one the virus strains are alive but weakened so that they do n’t do much grippe symptoms.
The one-year grippe vaccinum is recommended for certain groups of people which include aged, immature kids and people with low unsusceptibility and who have a opportunity of developing serious complications if they caught grippe.
Both these vaccinums and what is known as pre-pandemic vaccinums are different from the vaccinums made for the pandemic causation grippe viruses. The pandemic grippe vaccinum is made merely after the pandemic have started and the virus is isolated. The period from the start of the pandemic to the twenty-four hours when the vaccinum might be ready may be between 4 to 6 months. ( WHO,2007 )
Non-pharmacologic intercessions ; these may include simple hygiene steps like appropriate manus lavation and improved respiratory hygiene all the times to avoid spread from one individual to another. In instances of pandemics CDC recommended some other agencies of cut downing the spread such as shutting schools, utilizing respiratory defenders like masks and avoiding assemblage and crowded topographic points. ( CDC, 2007 )
Decision and future mentality
Influenza is one of the major causes of mortality and morbidity worldwide for many old ages now. The virus continues to germinate and new strains appear each twelvemonth ensuing in epidemics and sometimes pandemics. It remains a serious disease despite the handiness of antivirals and diffirent vaccinums, which are effectual for most people. Although the vaccinums used are helpful most of the times, new attacks are being developed. Specifically, cold-adapted live-virus vaccinums, which have been used in 1000000s of people outside the US, are now being considered for blessing by the FDA. Other second-generation live-virus vaccinums are being designed and tested in animate beings and are waiting to be studied in worlds. Major betterments, based on fresh adjuvants and recombinant DNA techniques, are looking frontward to alter the position of vaccinology against grippe.