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Table of Contents:

 

1. Swine Flu: The Facts

     a. Origins

     b. H1N1

     c. Transmission

 

2. The Risks and Dangers

     a. Mortality

     b.Comparison to Regular Flu

     c. Fatality Rate in Mexico

     d. People at Risk

 

3. What We Can Do

     a. Precautions

     b. Symptoms

     c. Medical Attention

     d. Treatments

     e. Neuraminidase

 

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1a. Swine flu has been in the news a lot but I’m not really sure what it is. What is Swine Flu? Where did it come from?

   

Swine Flu refers to the 2009 H1N1 virus that is spreading among humans worldwide. It is commonly called swine flu because studies have shown that the virus contains two genes from flu viruses that normally affect pigs (swine), bird (avian) genes, and human genes. This is known as a  “quadruple reassortant” virus.

 

This new virus was originally transmitted to humans in Mexico where it was passed on from a pig to a 5-year-old boy. From there, it has spread from person to person worldwide and in June 2009, the World Health Organization (WHO) declared the 2009 H1N1 flu outbreak as a pandemic. 

 

This diagram shows how a virus can jump from species to species:

http://www3.niaid.nih.gov/NR/rdonlyres/3D377A8B-747F-480A-832E-02A8ED9D1B3C/0/AntigenicShift_HiRes.jpg

 

Images of the H1N1 virus taken in the CDC Influenza Laboratory:

              

 

 

1b. What does H1N1 mean? From what did H1N1 evolve? Could the H1N1 virus, or its precursor, always infect humans?

 

H1N1 is a subtype of Influenza A, which is the most common type of all flu virus. H1N1 stands for the two sugar proteins that sit on the surface of the virus and enable its function. There are sixteen types of H protein, labeled H1 through H16, and 9 types of N protein. The H1N1 proteins are called hemagglutinin and neuraminidase. Hemagglutinin allows the virus to attach to human cells and neuraminidase allows new viruses to detach from the cell and spread.

 

 

The following diagram shows the evolution of the 2009 H1N1 virus:

  

 

1c. How is it transmitted? How does it attack your body?

 

Swine flu does not usually affect humans, but there have been random cases of infection prior to the current outbreak. Most people who contract swine flu work or live near pigs. Swine flu is capable of being transmitted from human to human, as displayed by previous outbreaks, as well as the current one. It spreads in similar ways to the ordinary seasonal flu – coughing or sneezing near someone, or touching something with the flu virus on it, and then touching the mouth or nose. Swine flu cannot be transmitted by eating pork because all viruses and bacteria are destroyed when the food is cooked. So don’t be worried about buying pork next time you are at the grocery store, as long as you properly cook the meat.  

 

The swine flu generally attacks host cells in the respiratory system. The virus injects its DNA into the cell and reproduces. Many other problems in the human body can come about from this such as, seizures, fever, vomiting, and dehydration. Additionally, swine flu can have consequences on the kidneys, the heart, and the immune system. Most deaths are caused by respiratory complications.

  

 

 

 

Swine flu's viral cycle consists of steps similar to other influenza viruses. The graphic above shows this cycle. (1) After the virus particle lands on a host cell, it binds to the cell's surface by using hemagglutinin, a spike-like protein sticking out of the virus' surface. (2) This causes the cell to take in the virus particle through endocytosis into a vesicle. (3) Protons are pumped toward the virus, causing the inside of the vesicle to become acidic. This changes the hemagglutinin spikes in a way that causes the hemagglutinin protein to bend, and thus it brings the membranes of the virus capsule and the host cell together. (4) The membranes fuse and a hole is formed. The viral contents are poured into the host cell's cytoplasm. (5) New viral proteins are translated from the mRNA in the viral contents. (6) They are then transported to sites where hemagglutinin and neuraminidase have been enveloping the host cell membrane. (7) New virus particles are created and released by budding, ready to infect a new cell. 

 

 

 

 

 

2a. How dangerous is it (Mortality)? Is Swine Flu really as dangerous as the media makes it out to be?

  

As of September 6, 2009, there have been over 277,607 confirmed cases of swine flu worldwide, and of those cases at least 3,205 deaths. However, these numbers are numbers may be lower than the true statistics because countries are no longer required to report individual cases due to the large number of people being infected. Although there was a high number of reported deaths from swine flu in Mexico, the mortality rate for swine flu is similar to that of the regular seasonal flu. 

 

What scientists are worried about is the possibility of a mutation in the genes that would create a virus more fatal to humans. For example, this novel virus could possibly combine with a drug-resistant strain already in existence. If this were to happen, the flu shot would be ineffective and the mutated swine flu would be able to rapidly spread throughout the population. Thus, the media has somewhat exaggerated how dangerous swine flu really is, but it should still be considered an important issue to watch out for. 

 

 

2b. How dangerous is it compared to the regular flu?

 

Seasonal influenza is more serious when it attacks the elderly (people 65 years of age or older) and about 90% of deaths caused by seasonal influenza in the United States are people in this age group.  However, deaths caused by swine flu in the United States affect a wider variety of age groups.  16% of deaths were in people ages 5-24, 39% in ages 25-49, 25%  in ages 50-64, and 20% in people 65 or older.  Therefore, statistics  have indicated that swine flu is more dangerous to younger people, while the elderly are more susceptible to the seasonal flu.

 

 

2c. Why was there such a high fatality rate in Mexico? 

 

Mexico is where the first cases of swine flu in humans began to appear. At that point, swine flu was a novel and unknown virus. Many people were unaware of swine flu until it became a widespread problem and they probably assumed it was the regular seasonal flu. For this reason, people were not as careful and sanitary. This created a perfect environment for the virus to spread. As a result, many people were infected, which lead to the large number of deaths.

 

 

2d. Who is at greater risk of catching swine flu?

 

There are certain groups of people who are considered to be at a higher risk of catching swine flu than others. This includes pregnant women and people with HIV, diabetes, and cardiovascular disease. Because swine flu affects the upper respiratory tracts, people with conditions such as asthma are at high risk as well. People in close contact with possible infected pigs, like in a pig barn or exhibits showing pigs at fairs, are at greater risk of catching swine flu. Also, children aged 6 months to 19 years and people with chronic conditions that weaken the immune system are considered to be at higher risk.

 

 

3a. What precautions should we take? 

       

There is a 2009 H1N1 vaccine currently being manufactured, and it will be ready for the fall season. For the time being, however, the precautions you should take are the same as with any illness. You should cover your nose and mouth with a tissue when coughing or sneezing. Wash your hands often with soap and water for fifteen to twenty seconds; alcohol-based hand cleaners also work. Avoid touching your eyes, nose, or mouth to avoid spreading germs. You should also avoid close contact with sick people. To prevent the spread of illness, you should stay home for at least 24 hours after your fever is gone. Your fever must be gone without the help of fever-reducing medicine.    

 

Of course, one of the most effective precautions is staying in good general health.  For example, you should get enough sleep, get enough physical activity, drink plenty of fluids, and eat nutritious foods.

  

 

3b. What are the symptoms?

 

The symptoms of swine flu are very similar to the symptoms of the seasonal flu. They include fever, cough, sore throat, runny nose, body aches, headache, chills, fatigue, and even diarrhea and vomiting. Some signs of swine flu in children are trouble breathing, bluish or grayish skin color, persistent vomiting, and being constantly irritable. Adults may experience sudden dizziness, confusion, difficulty breathing, or pain in the chest or abdomen. 

  

 

3c. Where do you go for help? 

 

To help prevent the spread of the flu, you should stay at home with a person to help take care of you.  You should ask your doctor if you need to be put on antiviral medication, but people usually don't need this unless they have a disease that weakens their lungs and breathing.  If the illness becomes emergent, which happens if a person has one or all of the following: difficulty breathing or chest pains, bluish discoloration of the lips, vomiting and inability to keep down liquids, dehydration or seizures, then you should seek immediate medical attention.

  

 

3d. What are the treatments? How does the current flu vaccine work? 

 

The CDC recommends using antiviral drugs oseltamivir (Tamiflu) or zanamivir (Relenza) to treat or prevent infection of the swine flu virus. These drugs are prescription medicine that keep the flu virus from reproducing in your body. They should be taken within two days of the appearance of symptoms. They lessen the severity of flu complications, and make you feel better faster.

 

Oseltamivir is used to treat some types of flu infections for people older than one year who have had symptoms of the flu for two days or less. It reduces the effectiveness of the virus by inhibiting the enzyme neuriminadase, causing viral particles to move to the host cell's surface and limiting the range of infection. Oseltamivir can be used to treat or prevent infections from bird flu and swine flu, but it does not prevent bacterial infections, which can be side effects of a viral infection.

Oseltamivir is an ethyl ester prodrug, which means it's an organic compound produced when an acid and an alcohol are combined. When it is in the body, it's converted to its active form, this form having medical effects.

 

Zanamivir inhibits the neuriminadase glycoprotein, which is important in the flu virus' infective cycle. It prevents the normal substrate of neuraminidase, sialic acid, by mimicking that substrate and occupying the active site of neuriminidase.

Whereas oseltamivir is usually in pill or suspension form, zanamivir is usually inhaled, so that its effects will happen sooner. 

 

 

3e. What is Neuraminidase? 

  

Neuraminidase is an enzyme on the surface of a virus cell that ensures that a virus leaving a cell does not get stuck on the cell surface. It works together with hemagglutinin, another surface protein which helps the virus enter the cell by inducing endocytosis. Neuraminidase binds to the polysaccharide chains of the virus and clips off the ends of the polysaccharide chains, allowing the virus to escape. This makes sure that the virus can spread more effectively through the host. The importance of neuraminidase when it comes to the flu virus is that the neuraminidase can mutate and even become lethal. If you have contracted the flu before, you are subject to contract it again because the neuraminidase may have mutated, resulting in the antibodies not recognizing the new flu. Antibodies do not recognize the new flu because the chemical structure of neuraminidase on the virus has changed after passing through various organisms. Neuraminidase is also important in the development of flu vaccines. The inhibition of the function of the neuraminidase protein prevents the virus from budding from the host cell, therefore stopping the flu from reproducing and spreading throughout the body.

 

A good visual of how a neuraminidase inhibitor works: 

 

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For more information:

 

CDC National Contact Center

Representatives are available 24/7 to answer your questions in English and Spanish. For up-to-date information about novel H1N1 flu and hundreds of other health and safety topics:

 

• Call: 1-800-CDC-INFO (1-800-232-4636), TTY: (888) 232-6348, English/Spanish, 24 Hours/Every Day

 

• Email : cdcinfo@cdc.gov

  

•       Postal Mail: 
Centers for Disease Control and Prevention
1600 Clifton Rd,
Atlanta, GA 30333
U.S.A. 

 

•      Or visit: http://www.cdc.gov/H1N1FLU/

 

 

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SOURCES 

 

Childs, Joanne, and Joy Livak. Personal interview. 18 Sept. 2009.

 

"Ester." Biology Online. N.p., n.d. Web. 17 Sept. 2009. http://www.biology-online.org    /dictionary/Ester.

 

"Hemagglutinin." RCSB Protein Data Bank. N.p., n.d. Web. 21 Sept. 2009. http://www.rcsb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/pdb76_1.html. 

 

"How Does the Flu Work?" Mother Nature Network. N.p., n.d. Web. 17 Sept. 2009.  http://www.mnn.com/earth-matters/translating-uncle-sam/stories/cdc-how-the-flu-works.

 

"Influenza Virus Hemagglutinin." Center for Biomolecular Modeling. N.p., 2008. Web. 25 Sept. 2009. http://cbm.msoe.edu/includes/swf/.

 

Kamps, Bernd Sebastian, Christian Hoffmann, and Wolfgang Preiser. "Oseltamivir." Influenza Report.

 N.p., n.d. Web. 17 Sept. 2009. http://www.influenzareport.com/ir/drugs/oselta.htm.

 

Keen, Anthony. "Influenza." University of Cape Town. N.p., n.d. Web. 18 Sept. 2009.  http://web.uct.ac.za/depts/mmi/jmoodie/influen2.html.

 

"Key Facts about Swine Influenza (Swine Flu)." Center for Disease Control and Prevention. N.p., n.d.  Web. 17 Sept. 2009. http://www.cdc.gov/flu/swineflu/key_facts.htm

 

Life Cycle of Influenza Virus. Chart. Flucentre. N.p., n.d. Web. 17 Sept. 2009.  http://www.flucentre.org/files/Life-cycle-of-influenza-vir.jpg.

 

"MIT Flu Central - Flu FAQ." MIT Medical. N.p., n.d. Web. 15 Sept. 2009. http://medweb.mit.edu/about/news/flu/flufaq.html.

 

"Origin of the Swine Flu Pandemic." Not Exactly Rocket Science. Seed Media Group, n.d. Web. 18 Sept. 2009. http://scienceblogs.com/notrocketscience/2009/06/origins_of_the_swine_flu_pandemic.php.

 

"Oseltamivir." Medline Plus. N.p., n.d. Web. 17 Sept. 2009. http://www.nlm.nih.gov/medlineplus/druginfo/meds/a699040.html.

 

"Pandemic (H1N1) 2009." World Health Organization. N.p., n.d. Web. 18 Sept. 2009.  http://www.who.int/csr/disease/swineflu/en/.

 

"Prodrug." Biology Online. N.p., n.d. Web. 17 Sept. 2009. http://www.biology-online.org/dictionary/Prodrug.

 

"Swine Flu: FAQ." cbanews.ca. N.p., 21 July 2009. Web. 17 Sept. 2009. http://www.cbc.ca/health/story/2009/04/24/f-swineflu-faq.html.

 

"Swine Flu Precautions." Berklee. N.p., n.d. Web. 17 Sept. 2009. http://www.berklee.edu/news/660/swine-flu-precautions.

 

"2009 H1N1 Flu." Center for Desease Control and Prevention. N.p., n.d. Web. 15 Sept. 2009. http://www.cdc.gov/H1N1FLU/.

 

"2009 H1N1 Flu (Swine Flu) and You." Center for Disease Control and Prevention. N.p., n.d. Web. 16 Sept. 2009. http://www.cdc.gov/h1n1flu/qa.htm.

 

"VIRUS PICTURES: Influenza Virus Replication or Flu Life Cycle." Russell Kightley Media: Science Graphics: Scientific Illustration and Animation. N.p., n.d. Web. 18 Sept. 2009. http://www.rkm.com.au/VIRUS/Influenza/lifecycle.html.

 

"What to Do If You Get Flu-Like Symptoms." Center for Disease Control and Prevention. N.p., n.d. Web. 17 Sept. 2009. http://www.cdc.gov/h1n1flu/sick.htm.

 

"Zanamivir." Influenza Report. N.p., n.d. Web. 17 Sept. 2009. http://www.influenzareport.com/ir/drugs/zanami.htm.

 

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This page was created and written by: Emily Haselton, Sarah Kim, Florence Ma, Alak Mehta, and Stephanie Sun.