H5N1: Is It Avian or Swine Influenza Virus Subtype?-新东方前途出国

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H5N1: Is It Avian or Swine Influenza Virus Subtype?

2020.02.17 浏览 来源：新东方前途出国综合

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摘要：What is H5N1? Does H5N1 Infect Humans? H5N1 Is It Avian or Swine Influenza Virus Subtype?

Part I: What is a Virus?

A virus is a biological agent, typically consisting of genetic material (either DNA or RNA) inside a protein shell (capsid). Like many ''living'' creatures, they carry genes and evolve. However, viruses cannot reproduce on their own. Instead, the virus must infect the cells of a living host, hijacking the cells' machinery, forcing it to reproduce thousands of copies.

This process, called the viral replication, starts with the virus attaching to the host cell and penetrating the cell wall or membrane. Once inside, the protein shell is uncoated, and the genetic material is released. This generic material is reassembled into new and some times evolved copies or new viruses. Eventually, the new viruses burst out of the host during a process called lysis, which kills the host cell. Because it kills its host cell, and the host cell is necessary for reproduction, the only way a virus survives is by spreading to other healthy hosts.

To date, we have identified over 5,000 different viruses that are very diverse. Most are species-specific and can only infect a narrow range of plants, animals, bacteria, or fungi.

Part II: What is Influenza?

Influenza, commonly known as "the flu," is an infectious disease caused by the influenza virus. There are four known types of influenza viruses: Influenza virus A, Influenza virus B, Influenza virus C, and Influenza virus D. They are all very similar in overall structure, and all contain glycoproteins, hemagglutinin and neuraminidase. For this reason, they are classified as H1N1, H1N2, etc. depending on the type of H or N antigens they express.

Only the first three: A, B, and C, are known to infect humans. Influenza virus A can also infect other mammals and birds. It is responsible for all known flu pandemics. Influenza virus B can also infect seals. Influenza virus C can also infect pigs and dogs. And Influenza virus D is only known to infect pigs and cattle.

Influenza virus A (flu) can cause mild to severe illness, and at times can lead to death. It should be noted that the flu is different from the cold. Symptoms of the infectious disease include but are not limited to: high fever, runny nose, sore throat, muscle and joint pain, headache, coughing, diarrhea, vomiting, and fatigue. Many of these symptoms are the result of your immune system fighting back against the virus.

Anyone can get the flu. Certain groups are at higher risk of developing serious flu-related complications, such as viral pneumonia, secondary bacterial pneumonia, sinus infections, and the worsening of pre-existing health conditions, which can arise. Therefore, adults 65 years and older, pregnant women, young children, and those with pre-existing conditions such as heart disease and stroke, diabetes, HIV/AIDS, cancer, and certain neurological conditions should remain vigilant.

Influenza virus A is so common that we can only estimate the number of people infected each year. In a ''low'' flu season, only 3% of the U.S. population gets infected and develops symptoms. In a ''high'' flu season, it is estimated that 11% of the population can be affected. Every year the virus evolves, and every year scientists around the world work together to produce vaccines, and anti-viral drugs to combat strains they believe will be most prevalent.

Preventative Actions:

1.Vaccination: This is the first and most important step in preventing the flu.

2.Staying away from people who are sick

3.Covering coughs and sneezes

4.Frequently washing your hands. This will prevent the spread of germs.

There have been cases where influenza virus A has mutated into particularly nasty strains that we have do not have vaccines or anti-viral drugs for. These strains have been the cause of several pandemics throughout history. Two notable pandemics are the 1918 influenza pandemic, also known as ''Spanish flu'', and in 2009, known as "swine flu" (H1N1).

Part III: What is H5N1?

H5N1 is a subtype of influenza virus A. The strain that is most commonly referenced in popular media as simply H5N1, avian influenza, or ''bird flu'' is HPAI A(H5N1) for highly pathogenic avian influenza virus of type A of subtype H5N1. It typicallycauses a highly infectious, severe respiratory disease in birds.

It is easily transmissible between birds through their saliva, nasal secretions, feces, and blood. Tens of millions of birds have died because of H5N1. Migratory birds such as wild ducks, geese, and swan can carry low-pathogenic H5N1 without becoming sick. This gives H5N1 the potential to spread around the globe. Of particular importance is its transmission to chickens— the largest population of any bird species. In 2016, global chicken production exceeded sixty-six billion birds.

H5N1 has radically changed poultry farming practices in several countries with some success. Mass poultry vacation has been implemented. They limit travel in places where the virus is found. Nevertheless, outbreaks do occur, and infections in the poultry industry have lead to the culling of hundreds of millions of birds to limit the spread of the virus.

Part IV: Does H5N1 Infect Humans?

Human cases of H5N1 influenza occur occasionally, but human to human transmission is difficult. Almost all human cases of H5N1 are the result of close contact with live or dead birds, or in H5N1-contaminated environments. There is zero evidence that the disease can be spread through properly prepared and thoroughly cooked poultry and game birds. Properly prepared and thoroughly cooked, because the virus is sensitive to heat, and temperatures of over 70°C will kill it.

Light Red: Countries that have reported deaths of poultry or wild birds linked to highly pathogenic H5N1 infection.

Dark Red: Countries that have reported human cases of highly pathogenic H5N1 infection.

What is concerning is the mortality rate in humans who have been infected, which sits at about 60%.

Symptoms of a flu infection:

· High fever

· Malaise

· Cough

· Sore throat

· Abdominal pain

· Chest pain

· Diarrhea

The infect can progress quickly to difficulty breathing and shortness of breath , pneumonia , Acute Respiratory Distress Syndrome , and neurological changes . If the virus were to undergo a generic change into a highly transmittable version among humans, it would be disastrous. There is no effective treatment for the H5N1 flu . Candidate vaccines are currently being developed, but they are based on the current strain of the virus and are not ready for widespread use.

A controversial study, conducted by an international team of researchers led by Kawaoka, a UW–Madison professor of pathobiological sciences and a leading expert on influenza, showed that some viruses now circulating in nature require just four mutations to the hemagglutinin protein , which sits on the virus surface and enables it to bind to host cells, to become an even greater threat to human health . Similar results have been found in labs in Rotterdam, Netherlands, and Harbin, China.

Note: Whether this will happen naturally outside the university laboratories, we do not know.

本文作者

Jonathan Javier

　　

加州大学洛杉矶分校-跨学科法语和法语研究学士学位

　　

Jonathan导师在美国电信巨头AT&T ，猎鹰投资，以及越南ESL等多个领域有过工作经历，为此累积了丰富的销售，市场以及教育行业的工作经验。十分致力于把他的全球视野和对教育的热情分享给新东方前途出国的学生们；另外他也希望自己多年来在加州大学学习生活的一手体验分享给更多的对加州大学感兴趣的学生们，为他们日后申请加州大学做好准备。

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