Avian Influenza Diseases

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

Every year, millions of people start talking about the influenza virus and getting their vaccines as the flu season approaches, which starts around the October-November period and reaches its peak between December and March. Therefore, public health officials around the world- and in the U.S in particular- are constantly challenged by properly preparing for the annual influenza dilemma, given that this viruses, and other respiratory viruses, are a serious health threat to the U.S population and the world as a whole. Furthermore, what makes the influenza virus even more challenging to control is that it can mutate rapidly and reassort to form new strains, having the ability to reside in multiple animal hosts. In fact, many scientists and researchers have been doing in-depth intensive research so as to understand the mechanism behind this unique characteristic of the virus, try to find new ways to control it, and explore different areas of protection and vaccination.

According to the CDC there was a breakout in “1918-19 Flu pandemic, which killed as many as 50 million people worldwide”causing the biggest breakout for Influenza (Reconstruction of 1918 Influenza Pandemic Virus). Influenza originated from Asia and the Middle East. Virtually all mammalian species have influenza. Influenza is a contagious respiratory illness caused by the Influenza virus. There are three types of Influenza: type A, type B, and type C. Influenza has numerous symptoms, vaccinations, and is unlikely to kill it’s host.

Influenza remains as a significant global threat to public health. In United States alone, a typical influenza epidemic results in over 25 million infections, 300,000 hospitalizations and 13,000 deaths every year (1). The virus evolves antigenically from one year to the next, requiring annual reformulation of the vaccine and leading to variable vaccine efficacy. Exacerbating this natural antigenic evolution, adaptation to the chicken eggs may occur during the manufacture of virus used to produce the inactivated vaccine (2). This year such adaptation has reduced the vaccine efficacy against H3N2 strain (3). Low vaccine efficacy is expected to generate higher attack rates, as has already occured in Australia (3, 4). Compounding the effects of low vaccine efficacy, public perception following the widespread media attention may depress vaccine uptake for a given year. The combination of low vaccine efficacy and low coverage has the potential to reduce herd immunity, putting the population at risk of elevated infection incidence and ultimately high rates of infections and mortality. Consequently, optimizing epidemiological effectiveness of vaccination given vaccine efficacy is imperative to minimize the annual mortality and morbidity of influenza.

The emergence of the “Hong Kong Flu” in 1968-1969 marked the beginning of the A(H3N2) days. When this virus first emerged it had the lowest mortality rate in the 20th century. Although this virus first emerged with such a small death rate, it still continues to kill people to this day. Just as when the A(H2N2) virus appeared in 1957 causing the disappearance of the A(H1N1) virus, the appearance of the A(H2N3) virus caused the disappearance of the A(H2N2) virus. After being dormant for almost 30 years, the A(H1N1) virus reappeared and today

Wild aquatic fowl, ducks in particular, serve as a reservoir for the Influenza virus to transmit into poultry and then to humans. Infected birds shed flu viruses in their saliva, nasal secretions, and feces (CDC, 2004). The current virus seen in Asia is denoted as H5N1 and was first seen in terns in South Africa in 1961 (CDC, 2004). The first human seen infection of the avian H5N1 viruses was in 1997 in Hong Kong in a three- year old boy (Ruben, 2005). The outbreak involved 18 cases and killed 6, one third of the confirmed infected population (Rueben, 2005). In three days 1.5 million birds were killed in order to prevent further spread. A new pandemic is now on the horizon with recent outbreaks in poultry in the eight Asian countries of Cambodia, China, Indonesia, Japan, Laos, South Korea, Thailand, and Vietnam since 2004 (CDC, 2005). As of July 5, 2005, there have been 108 reported human cases of the H5N1 virus with 54 deaths (CDC, 2004). In wake of a

Once there was a virus named Birdie. This virus was a Bird Flu, or Avian Influenza, virus of the subtype H5N1, the first strain of Avian Influenza having the ability to infect humans (Normandin and Solan). Birdie looked like a microscopic pomander, a fragrant orange with cloves stuck in it. Inside, she had eight pieces of single stranded ribonucleic acid or ssRNA. Birdie was deadly to humans, but was not able to spread from one human to another. She could only spread from birds to humans ("Bird Flu"). Birdie started out inside a chicken named Cluck, where she was formed. A little while later, Cluck's farmer Mark, sold his Cluck, to Joe, another poultry farmer because Mark did not realize that Cluck had H5N1. After a few months of Cluck living

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 outlook for the bird flu viral infection depends on how intense the infection becomes and on the specifics of each strain.

It is believed that humans first contracted the disease when animals were first domesticated. The term “influenza” was originally coined in 1357 AD from an Italian word meaning “influence”. The first true report of the disease was in 1694. It was not until 1933 that influenza was identified as a virus (Taubenberger, Reid, and Fanning 30). The first documented pandemic was in 1580, where it spread throughout the Asia Minor, North Africa, and Italy (White). Since the first influenza pandemic, there have been six major influenza pandemics. These major pandemics began in the years 1889, 1918, 1957, 1968, 1997, and 2009 (Gibbs and Soares

Influenza A virus is extremely virulent and is known for being the most severe type of influenza. This type of virus generally resides in aquatic birds, which act as hosts for the virus. However, influenza A is capable of being transmitted to other species which

Influenza type A viruses are divided into subtypes based on two proteins on the surface of the virus. These proteins are called hemagglutinin (HA) and neuraminidase (NA). There are 15 different HA subtypes and 9 different NA subtypes. There are three prominent subtypes of influenza A that are known to infect both birds and people. The first one is influenza A H5; there are nine known subtypes of H5 viruses (H5N1, H5N2, H5N3, H5N4, H5N5, H5N6, H5N7, H5N8, and H5N9). Most H5 viruses identified worldwide in wild birds and poultry are low pathogenic viruses, but occasionally highly pathogenic viruses have been detected. Sporadic H5 virus infection of humans, such as with Asian-origin highly pathogenic avian influenza A (H5N1) viruses currently circulating among poultry in Asia and the Middle East have been reported in 16 countries, often resulting in severe pneumonia with approximately 60% mortality worldwide. The second one is influenza A H7; there are nine known subtypes of H7 viruses (H7N1, H7N2, H7N3, H7N4, H7N5, H7N6, H7N7, H7N8, and H7N9). Most H7 viruses identified worldwide in wild birds and poultry are LPAI

In general, detection of influenza reassortment requires screening of segment phylogenetic trees, where tree incongruences point to differences in segment evolutionary history. Until recently, intra-subtype reassortment has been studied by manual comparisons of segment phylogenies, a highly time consuming task imposing restrictions on the size of the data and the depth and detail of the analyses. In addition, higher relatedness of sequences from the same subtype leads to a less pronounced phylogenetic signal, making detection of recent and subtle reassortments particularly challenging [21, 23, 27, 28]. Latest developments of automated tools for detection of influenza reassortment have allowed for bigger and more thorough analyses, and by accounting for uncertainties in inferred phylogenies, have also made the identification of reassortment a more robust process [20, 25, 28, 29]. This has contributed to our understanding of the occurrence and the impact of influenza intra-subtype reassortment, however, a detailed knowledge of the reassortment rate and global distribution is still lacking. In this study we utilize the latest advanced approaches, and in combination with more conventional phylogenetic analyses, we determine the global burden, frequency, and distribution of H3N2 intra-subtype

Influenza is a virus that is transmitted mainly via airborne process, which is one of the fastest mode of transmission. It is transmitted though airborne due to symptoms such as coughing and sneezing of the host (the infected). The host sneezes and coughs, influenza can easily be transmitted the agent via droplets and small microorganism, therefore entering the uninfected though the respiratory system (mouth and nasal) (WHO, 2016). Another way the virus can lead to pandemic, is due to the fact that the number of human and animals continue to grow and interact. Thus, the pandemic of influenza type A is possible. This mode of transmission is both and; the airborne (respiratory system) and physically (hand contamination). The customarily begins in rural areas (farms) as the virus can be found in hosts such as horses, pigs, chickens and birds. There has been an undetected interchange of the disease among animals and humans in rural environments which then eventually grows to become a global pandemic (Webster, RG & Monto, AS et al 2013, Textbook of influenza). The virus may continue to spread physically due to hand contamination in public; these may include door handles, public transport and other hand held hold objects. The last mode of transmission is genetically, this may then lead to asthma or even death (WHO,

As already mentioned, the H5.N1 is a subtype of an influenza A type. This type consists of RNA. This RNA names as HA and NA. The HA is glycoproteins found on the surface of the virus. This special protein helps the virus to bind to the host cell. While NA is glycosylated enzyme sits on the surface as well. It helps to release the virus from the host cell. In reality, the least pathogenic virus is H5.N1 or (LPAI H5N1), is commonly happening in wild birds for example, in 1983 it is reported that the virus being carried by the ring-billed gulls in Pennsylvania, ( Bird flu (H5.N1) Genetic in news-medical). The virus itself cannot be pathogenic unless some changes occur, which means new progeny. When the RNA of two viruses enters a combination process in the host cell.