Viruses : The Human Immune System

According to Center for Disease Control (CDC), influenza viruses are divided into three types, designated as A, B, and C. Influenza type C usually only causes either very mild symptoms or no symptoms at all. Types A and B, however, are responsible for epidemics of respiratory illnesses that can result in hospitalization, or even death. Influenza is constantly changing over time by mutations. This continual change allows the virus to evade the antibodies that were meant to kill it. A host infected with influenza virus develops antibodies against that virus; as the virus changes, the "first" antibody no longer recognizes the "newer" virus and infection can occur because the host does not recognize the new flu virus as a problem until the infection is well under way. The first antibody developed may, in some instances, provide partial protection against infection with a new influenza virus. According to Medicine Net.com, In 2009, almost all individuals had no antibodies that could recognize the novel H1N1 virus immediately. It quickly spread throughout the world so fast that the WHO declared this new flu strain (termed novel H1N1 influenza A swine flu). There are currently four main strains of influenza circulating worldwide. Three of the viruses are type A, and one is type B. Type A viruses are divided into subtypes based on the differences in two viral proteins called hemagglutinin (H) and neuraminidase (N). The three subtypes of influenza A are A(H1N1), A(H3N2), and A(H5N1). The reason for several strands of type A are because of the two kinds of change influenza A

The immune system depends on the body’s structures to help it function. For instance, the skin acts as the “body’s first line of defense.” If a pathogen finds a breach in the skin barrier, it is the circulatory system that must now signal the immune system of the invader. Shortly after, white blood cells will be notified of the infection and will target and destroy the pathogen.

The body’s protection against viruses, bacteria and other types of invasions is our immune system (Tortora, 2014).

There are there types of influenza A and C or the most severe types and B which is the most common, Luckily not the to severe. The virus works by first attaching to the outside of a host cell. It injects its RNA into the cell. Unfortunately our cells treat the RNA like they should. It translates the viral genes using the cell’s ribosomes and enzymes. Now the virus can take the cell over and use it to reproduce more viruses. Sooner or later it releases the new nauseating viruses and they search for another cell to raid.

The immune system is an important and complex part of the human body, guarding it against bacteria

There are two important proteins used in the determination of the type of influenza; haemagglutinin (HA) and neuraminidase (NA). There are 18 known variations of the haemagglutinin protein and 11 of the neuraminidase protein, giving hundreds of possible variations in the subtypes of the virus . These subtypes are further divided into different strains that have a divergent molecular makeup, giving rise to viruses that differ in virulence, ease of transmission and severity of symptoms. Not all strains of influenza can cause disease in humans; influenza D subtypes cannot infect humans and influenza C infections are rare and usually very minor. Influenza A and B are the subtypes that are responsible for the common infections and the epidemics and pandemics that occur periodically, with influenza A causing the majority of these infections. The virus is transmitted through the inhalation of droplets which are expelled when an infected person coughs or sneezes, through contact with a contaminated surface and through the exchange of saliva . The infected person becomes infectious to others around 12 hours after first contact with the virus and remains contagious for around the next five days; this can vary as the immunocompromised can take longer to subdue the virus and children tend to be more infectious than adults . The virus incubates in the respiratory tract by invading cells through the cleavage of the viral protein haemagglutinin by human proteases . The pathogenicity of a certain strain is determined by the spread of proteases in the respiratory tract that can cleave the proteins of the virus; a strain is typically milder if the proteases that reside in the lungs and throat are the only ones capable of cleaving the virus, causing an upper respiratory tract (URT)

The influenza virus thrives because of its unique characteristics that allow it frequently change and undergo evolution. The influenza virus has a segmented genome meaning that each section of RNA is copied separately allowing reassortment to play a major role in the evolution of the influenza virus. When two different strands of the virus attack the same cell, both strands of RNA are copied in the nucleus. These copies then move to the cytoplasm where new viruses are compiled. Each new virus needs all eight of its genomes which can come from a copy of either of the original infecting viruses. The new virus would then have a mixture of RNA from each originating virus causing it to be different from both (Rahnama, L, et al., 2013). Reassortment causes new strains of viruses

Influenza is a life threatening illness caused by influenza virus. It is a contagious disease of the respiratory tract causes serious infections and death around the globe usually in winter season. There are three types of influenza viruses infect humans, type A, B and C. Influenza A and B cause severe disease and major outbreaks and can be prevented through influenza vaccination. Influenza C causes common cold like illness among children. Influenza A is responsible for influenza pandemics. Influenza A and B viruses have two main proteins on the outside of virus, the haemaglutinin (H) and the neuraminidase (N) proteins and are referred as antigens as they are the structures to which our immune system responds. New strains of influenza A and B continually form because the H and N antigens change.

IAV is a virus classified as part of the orthomyxoviridae and one of the causative agents of influenza or “the flu”. (Edinger, Pohl & Stertz, 2014) Its natural reservoir is primarily wild aquatic fowl where it is mostly nonpathogenic, though zoonotic infections can occur in mammals and domestic fowl. (Klenk, Matrosovich & Stech, 2008) The jump between species often results in the establishment of highly pathogenic variants that can have devastating effects, as was the case of the “Spanish” influenza pandemic of 1918. (Taubenberger, 2006) The infection across special barriers is dependent on changes to the structure of glycoproteins on the viral envelope, particularly haemagglutinin (HA). The different subtypes of HA and neuraminidase (NA) serve to classify different viral lineages. These changes in the structure can result in proteolytic activation; that when coupled to changes of receptor binding specificity allow for interspecies transmission. (Klenk, Matrosovich & Stech, 2008) The modifications can affect the pathogenicity of the virus even within the same species, which can allow for infection of new cell types, or even systemic disease. (Steinhauer, 1999) These mutations accumulate through successive replications or genetic re-assortment during confection. The resulting structural changes account for the observed antigenic drift that causes loss of immunity despite prior exposures to the virus. This evolutionary process drives the consistent

Structure: The influenza virus looks like a sphere covered with spike like proteins for grip ready to latch on to a healthy human cell. “The H spike (hem agglutinin) and the N spike (neuraminidase) are called proteins and exist in the envelope and they are used for antigenic typing” (Pearson 2004). These proteins allow the virus to enter and exit the host (our cells). Once the virus is inside the cell, the virus can begin reproducing. Soon, each infected cell is filled with thousands of new viruses, each of them looking to leave the cell to find a new home in another cell and begin reproducing there.

Ebola hemorrhagic disease, rabies, influenza and HIV are examples of RNA viruses and a few of these viruses have yet to be thoroughly researched. An example of an RNA virus that mutates and evolves at a high rate is the influenza virus. The influenza virus can mutate in two different ways; antigenic shift which is an abrupt change and by antigenic drift which is a smaller, more gradual change that occurs through point mutations (Uyeki 2014). These changes are what help the virus to evade the host 's immune system. Another

Influenza A, B, and C viruses are responsible for epidemics in humans. They are “characterized by a segmented, single-stranded ribonucleic acid (RNA) genome” (Grossman & Porth, 2014, p. 932). The influenza A virus contains 2 subtypes: hemagglutinin

Viruses cause a wide variety of human diseases. They travel easily person to person contact or touching contaminated areas. Once in the body they reproduce quickly after enduring cells. Respiratory infections are caused by Rhinovirus, coronavirus and adenovirus are the cause of a common cold. Influenza virus infect your upper respiratory system and can potentially spread to the lungs causing pneumonia. Digestive system infections such as the stomach flu is caused by a virus such as calicicirus and astrovirus. Skin infections are another disease caused by viruses. Chicken pox is a disease in which itchy fluid-filled bumps on the skin form and eventually bust or scab over. This virus is called the varicella virus. It also can cause shingles which

With a huge number of victims, 80 to 100 million, since 1918, the influenza is considered as one of the most pandemic diseases ever. There are three types of influenza virus: influenza virus A, influenza virus B, and influenza virus c. These are a subtypes of the virus family orthomyx-oviride. The types B and C do not cause pandemic diseases while type A does. The type A classified into three main subtype H1.N1, H1.N2, and H3.N2. The (H.N) refers to the two kinds of proteins on the surface of the virus (hemagglutinin and neuraminidase). The difference in numbers is due to the difference in protein variability. A H1.N1 virus which is widely known as Spanish flu is the only type that can transmit from human to human. The H5.N1, or “bird flu”

Our immune system is the second most complex system in our body. It is made up of organs, cells and proteins that work together to protect our bodies from harmful bacteria, viruses or other microorganisms that can cause diseases. Usually we don’t notice our immune system defending us against pathogens, but if the pathogen (harmful microorganism) is aggressive or if our body hasn’t ever come into contact with it, we can get sick. The jobs of our immune system are to recognise pathogens, as well as neutralise and remove them from our body. Our immune system also has to fight our own cells if they have changed due to an illness, for example, cancer. (1)