听力原文：Narrator Now get ready to answer the questions. Professor Hello, class. I guess youve all heard about swine flu these days. In fact, the World Health Organization says the swine flu outbreak is moving closer to becoming a pandemic. So, today Ill begin with the basics about swine influenza. Swine influenza(also swine flu)refers to influenza caused by any strain of the influenza virus endemic in pigs(swine). Strains endemic in swine are called swine influenza virus(SIV). Of the three genera of human flu, two are endemic also in swine: Influenzavirus A is common and Influenzavirus C is rare. Influenzavirus B has not been reported in swine. Within Influenzavirus A and Influenzavirus C, the strains endemic to swine and humans are largely distinct. Well, swine flu is common in swine and rare in humans. People who work with swine, especially people with intense exposures, are at risk of catching swine influenza if the swine carry a strain able to infect humans. However, these strains infrequently circulate between humans as SIV rarely mutates into a form. able to pass easily from human to human. In humans, the symptoms of swine flu are similar to those of influenza and of influenza-like illness in general, namely chills, fever, sore throat, muscle pains, severe headache, coughing, weakness and general discomfort. Diana Excuse me, Professor, may I ask a question? Professor Yes, please, Diana. Diana As we know, the flu outbreak of this year started in Mexico. Then, why has it infected to humans? Professor A very good question. Well, the 2009 flu outbreak in humans is due to a new strain of influenza A virus subtype H1N1 that derives in part from human influenza, avian influenza, and two separate strains of swine influenza. The origins of this new strain are unknown, and the World Organization for Animal Health(OIE)reports that it has not been isolated in swine. It passes with apparent ease from human to human, an ability attributed to an as-yet unidentified mutation. The strain in most cases causes only mild symptoms and the infected person makes a full recovery without requiring medical attention and without the use of antiviral medicines. Tom Then, Professor, how should we prevent it? Professor Influenza spreads between humans through coughing or sneezing and people touching something with the virus on it and then touching their own nose or mouth. Swine flu cannot be spread by pork products, since the virus is not transmitted through food. The swine flu in humans is most contagious during the first five days of the illness although some people, most commonly children, can remain contagious for up to ten days. Diagnosis can be made by sending a specimen, collected during the first five days, to the CDC for analysis. Recommendations to prevent spread of the virus among humans include using standard infection control against influenza. This includes frequent washing of hands with soap and water or with alcohol-based hand sanitizers, especially after being out in public. Although the current trivalent influenza vaccine is unlikely to provide protection against the new 2009 H1N1 strain, vaccines against the new strain are being developed and could be ready as early as June 2009. Experts agree that hand-washing can help prevent viral infections, including ordinary influenza and the new swine flu virus. Influenza can spread in coughs or sneezes, but an increasing body of evidence shows little particles of virus can linger on tabletops, telephones and other surfaces and be transferred via the fingers to the mouth, nose or eyes. Alcohol-based gel or foam hand sanitizers work well to destroy viruses and bacteria. Anyone with flu-like symptoms such as a sudden fever, cough or muscle aches should stay away from work or public transportation and should see a doctor to be tested. Social distancing is another tactic. It means staying away from other people who might be infected and can include avoiding large gatherings, spreading out a little at work, or perhaps staying home and lying low if an infection is spreading in a community. Now get ready to answer the questions. You may use your notes to help you answer. 11. What is the lecture mainly about? 12. In the lecture, the professor describes three types of influenzavirus. Indicate whether each word or phrase describes the three types of influenzvirus. Tick the correct box for each type of influenzavirus. 13. According to the professor, who are the most likely to catch swine influenza? 14. What are the symptoms of swine flu? 15. What does the professor imply when he says this? Professor Well, the 2009 flu outbreak in humans is due to a new strain of influenza A virus subtype H1N1 that derives in part from human influenza, avian influenza, and two separate strains of swine influenza. 16. What can be done to prevent swine flu?Narrator Listen to part of a lecture in an epidemiology class. Now get ready to answer the questions. You may use your notes to help you answer.
What is the lecture mainly about?
A．The definition of swine flu in Mexico.
B．The basic information about swine flu.
C．The infection of swine flu to humans.
D．The prevention of swine flu worldwide.
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