Written by Sang K. (KIS'19)
Edited by Sarah O. (KIS '19)
━━ April 3, 2018 ━━
The Biology Behind its Appearance and its Evolution Between Organisms
Influenza or the “flu” is a virus that has dangerous capabilities to evolve and infect the human population. The influenza contains RNA and functions to transport its genetic information into a host in order to further replicate itself. Therefore, the influenza virus has specific proteins on the surface that can help it interact with our (human) cells and possible enter in order to replicate itself further. Hemagglutinin, influenza most known protein, is used to grab onto the sialic acid of the human cell, allowing the virus to enter the cell. Once the virus has entered the cell, it starts releasing its RNA and genetic products into the cell, which eventually reaches the Nucleus, the factory for replication. At this point, the cell is used as a viral factory to create more and more viral products such as the RNA, hemagglutinin, and neuraminidase. Eventually, the daughter cells (virus) will want to leave the human cell and go off to replicate more. Therefore, it uses the neuraminidase protein that is located on the membrane in order to cut the sialic acid and exit the human cell. From there, the virus will once again enter another cell using its viral membrane proteins. The symptoms we receive from influenza is caused by the death of infected cells and their contents leaking into the cellular environment. These dead cells can produce the contents you see when you have a runny nose, sore throat, inflammations, and coughs.
━━━━━━━━
But what's so different about influence? Why is it so special?
Well, Influenza has a tendency to mix its genetic information with other viruses when entering the same cell. In some cases, two different influenza viruses (that you might already be immune to) might enter a cell simultaneously to replicate its RNA and genetic information. Each virus will create its own set of viral proteins and genetic information to input in their daughter cells for when they exit the human cell. However, in the process of packaging this genetic information into its daughter cells, the two viruses’ genetic information may mix and end up in one daughter cell, creating a new variation. This new variation may have different genetics from its parents and could create different membrane proteins which are shaped differently.
The reason why this is a major problem is that vaccines are specifically used to train your body when there is an attack. With the already known influenza viruses, it is easy to create a corresponding vaccine and within two weeks, you will be immune to that strain of influenza. A vaccine specifically trains your immune system, in the form of memory T cells, to react more efficiently to that specific virus and know what specific antibodies to create for that specific infection. These antibodies suppress the virus by binding to its receptor sites and its membrane proteins, to block the virus from entering/interacting with cells. These memory T cells store that information about what antibody to use for what infection, and therefore when you get the same viral infection the second time, your body is able to fight it off in a shorter amount of time and expending way less energy. But if we go back to the issue of different strains combining their genetic information to create a new genetic identity, those new combinations of genes will create new membrane proteins, ones that your antibodies will no longer fit. Therefore, you end up creating a new strain of influenza that is resistant to your vaccine and its corresponding antibodies, as the different shape and combination of viral membrane proteins no longer allow the antibodies to fit and suppress the virus’s activity. That’s why you need to get a new flu shot that will provide you immunization on that new strain of virus and why you need a flu shot every year.
The Connection to Animal Influenza
If you lived anywhere near China or Korea, you probably heard of the Animal Influenza and its massive damage on farm animals. It’s probably the reason why your chicken prices surged during 2013-2015. The most commonly known strain is the H7N9 bird flu strain that appeared in China and, according to the World Health Organization, has infected 900 people and killed around 300 people as of January 2017. Avian influenza or zoonotic influenza is the mixture of virus contents from pigs, poultry, and people. This extensive lineage is the reason why it is so difficult to find a specific cure/vaccine for this virus.
There are mainly two types of Influenzas: Influenza A and Influenza B. Type A exists mostly within animals such as poultry, pigs, cats, and other mammals. Influenza B is the virus that shows the most occurrence around humans. Type A can be transmitted to a ducks, pigeons or other birds. Depending on the strain, Avian influenza A can do severe damage or passive damage to its host. However, the point is that birds work as easy transmitters for this specific strain of Avian Influenza A. Swine Flu or H1N1 mostly circulates around pigs and humans. But the biggest problem doesn’t arise from humans. It’s actually the pigs. The pigs are the reservoir for infection as they can be infected with the common human influenza, avian influenza and the swine flu simultaneously. Because the pigs are vulnerable to avian influenza and swine flu, they can get infected by these humans and birds that carry such flus concurrently. With the pig’s internal body containing both the avian and swine flu at the same time, these viruses can attack the same cells simultaneously and possibly mix their genes in the process of gene replication. When this occurs, the mixture of genes can create a new strain of influenza with a new combination of genes and a new arrangement of membrane proteins.
H7N9 is a specific case for this reassortment of genes. It has been found that most of the reassortment of genes have come from the avian influenza viruses of domestic ducks, chickens and wild birds. As each strain of virus contributed a different factor towards the new H7N9 virus, we can also identify where each of these genes originated from. The domestic ducks carrying the H7N3 virus provided the hemagglutinin genes, while the wild birds with the H7N9 virus provided the neuraminidase genes, and the domestic poultries (such as chickens) with several H9N2 viruses provided the rest of the remaining base genes for the new H7N9 virus. Therefore it is also known as the “bird flu” as its genes were heavily influenced by the previous infections from birds.
One of the first human infections occurred during an interaction between a Chinese man and a domestic poultry in a poultry market. Although the possibility of a human-human transmission is possible, scientists have found that it was a very low possibility. But surprisingly, the transmission from poultry to humans was unexpectedly high as birds had infected their feces, saliva and mucus with the avian influenza virus. People who touch these birds without proper protection are likely to touch contaminated areas of the bird and receive the virus. It has also been recorded that the virus can also be transmitted through dust and droplets, which humans can inhale and become infected. According to the Centers of Disease Control, Symptoms of H7N9 include not only common signs such as fevers, vomiting, nausea, coughing, sweating, diarrhea but also severe respiratory problems such as breath shortening, difficulty in breathing and pneumonia. There has also been some severe cases of deaths caused by organ failures and cytokine release syndrome, where your body’s immune system becomes overstimulated, experiences the excessive inflammation, and surges cytokine release that actually causes more damage to your body rather than protecting. When your body tries to overprotect itself, it may also act against you as individuals experiencing a cytokine storm can experience, low blood oxygen levels, seizures, hallucination, fast breathing, muscle pain, and abnormally high nitrogen levels in the bloodstream, which can lead to kidney failure.
Diversity is often seen as a beauty within our society. There have been many times when diversity has been a saving factor for humans. A clear example is the sickle-cell anemia and malaria situation. With the diverse environments, sickle-cell anemia is actually an advantage in African regions as it provides temporary immunity to malaria, and therefore the gene pool still consists of the sickle-cell gene, whereas in America, where Malaria isn’t present, the gene pool shows a fairly low population of sickle-cell genes. Diversity has allowed us to learn more about the effects of environments as well as the survival factor of species. More diversity within a group of species often means more chances that one of those variations will be the “adaptive” trait and will survive when certain genetic drift events occur. Diversity ensures that our species don’t experience extinction. The nature which breeds our diverse individuals and environments also sometimes creates factors which work against our favor. The diversity of viruses and diseases certainly do not work in our favor as the different variations and mixing of genetic properties create new drug-resistant diseases, which work against our line of defence. But the important thing to understand here is that diversity works in every way possible and that nature doesn’t have only one method to adjoin differences. We may often learn in our biology classes that diversity is limited to a species’s variation and how we differ from one another. However, research in new viruses such as the H7N9 show that diversity can occur across different species and organisms. Those diverse backgrounds and genetics that originate from a different species can be accumulated with our own internal information to develop new properties and characteristics. These discoveries not only trace the importance of learning the differences between humans but also guides the community to realize the importance of recognizing the variations and similarities across species and how those subjects of nature can possibly interact with one another.
━━━━━━━━
Bibliography:
- "Avian Influenza A Virus Infections in Humans." Centers for Disease Control and Prevention. Centers for Disease Control and Prevention, 18 Apr. 2017. Web. 07 Feb. 2018. <https://www.cdc.gov/flu/avianflu/avian-in-humans.htm>.
- "Influenza (Avian and Other Zoonotic)." World Health Organization. World Health Organization, n.d. Web. 07 Feb. 2018. <http://www.who.int/mediacentre/factsheets/avian_influenza/en/>.
- Levitt, Alexandra M. Deadly Outbreaks: How Medical Detectives save Lives Threatened by Killer Pandemics, Exotic Viruses, and Drug-resistant Parasites. New York, NY: Skyhorse, 2015. Print.
- Normile, Dennis. "Bird Flu Strain Taking a Toll on Humans." Science | AAAS. N.p., 08 Dec. 2017. Web. 07 Feb. 2018. <http://www.sciencemag.org/news/2017/02/bird-flu-strain-taking-toll-humans>.
- Steenhuysen, Julie. "New H7N9 Bird Flu Strain in China Has Pandemic Potential: Study." Reuters. Thomson Reuters, 19 Oct. 2017. Web. 07 Feb. 2018.<https://www.reuters.com/article/us-health-birdflu-pandemic/new-h7n9-bird-flu-strain-in-china-has-pandemic-potential-study-idUSKBN1CO2DD>.
- "Transmission of Influenza Viruses from Animals to People." Centers for Disease Control and Prevention. Centers for Disease Control and Prevention, 12 Apr. 2017. Web. 07 Feb. 2018. <https://www.cdc.gov/flu/about/viruses/transmission.htm>.
- Wang, Qinghua, and Yizhi Jane. Tao. Influenza: Current Research. Norfolk: Caister Academic, 2016. Print.
Pictures:
- The images within the article are drawn by Sang Kim.
━━━━━━━━
Comments