Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Viral phylodynamics wikipedia , lookup
Ebola virus disease wikipedia , lookup
Social history of viruses wikipedia , lookup
Introduction to viruses wikipedia , lookup
Plant virus wikipedia , lookup
Oncolytic virus wikipedia , lookup
Virus quantification wikipedia , lookup
Henipavirus wikipedia , lookup
PART FOUR: QUESTIONS 16-20 Read the following article on flu and circle the best answer for each question. (0) has been done for you as an example Scientists believe they have uncovered a key reason why flu viruses tend to strike in cold weather. They found the viruses coat themselves in fatty material that hardens to a gel, protecting them from exterior influences. This coating melts in the higher temperatures of the respiratory tract, allowing the virus to infect cells. The US National Institutes of Health Team hope their study, which features in the journal Nature Chemical Biology, could lead to new treatments. However, a UK expert said the discovery did not explain why some flu viruses also thrived in tropical climates. The hard rubbery coating around the virus, which forms in colder temperatures, gives it the protection it needs to pass from person to person. The coating is so robust it can even resist to certain detergents. However, once inside a host the virus can only infect a target cell once the coating has melted. But this liquid phase is not tough enough to protect the virus against the elements, and so if the protective coating melts when the virus is outside the host, it dies. Dr Duane Alexander, director of the National Institute of Child Health and Human Development, said: "The study results open new avenues of research for preventing winter flu outbreaks. Now that we understand how the flu virus protects itself so that it can spread from person to person, we can work on ways to interfere with that protective mechanism." The researchers used a sophisticated magnetic resonance technique to create a detailed fingerprint of how the flu virus's outer membranes responded to variations in temperature. The virus's outer membrane is composed chiefly of molecules known as lipids, such as oils, fats and cholesterol. The researchers found that at temperatures slightly above freezing, this lipid covering turned into a gel. However, as temperatures approached 15.6C (60F), the covering gradually melted. The researchers concluded that temperatures in the spring and summer were too high to allow the viral membrane to enter its gel state. As a result, at these temperatures the individual flu viruses would dry out and weaken - accounting for the end of the flu season. Professor John Oxford, an expert in virology at Queen Mary College School of Medicine, London, said the paper was interesting, but it might be premature to draw firm conclusions. He said: "If this is the case why do we get flu in tropical areas, where the temperature is 35C (95F) all the time?" Professor Oxford said researchers had tried to link flu infection definitively to cold weather since the great Russian outbreak of 1890, but had failed to come up with conclusive proof of a link. "I don't think this study provides anything like a definitive answer on the spread of the virus - there must be some other factors that come into play," he said. (0) According to the author, viruses resist: a) high temperatures b) low temperatures c) temperature changes d) doesn’t say (16) The American scientists: a) want to get their work published soon b) hope new therapies will be developed c) need to do some further researches d) need more help from other experts (17) The virus’s protective layer: a) can only be destroyed by immune system b) does not react to any chemical substances c) hardens when it gets inside human body d) melts before the virus attacks host’s cells (18) When Dr Alexander talks about this discovery he is: a) pessimistic b) uncertain c) optimistic d) worried (19) The researchers, the virus’s protective coat weakens when: e) it is exposed to magnetic field f) It contacts the lipid molecules g) winter ends and spring begins d) outside temperature goes up (20) Professor Oxford states that this study: a) isn’t relevant for flu prevention b) ignores some important facts c) has not been finished yet d) focuses on climate changes Key: 16. b 17. d 18. c 19. d 20. b