考博医学英语-389.doc

考博医学英语-389
(总分：100.00，做题时间：90分钟)
一、PartⅠ Listening Comp(总题数：0，分数：0.00)
二、Section A(总题数：3，分数：15.00)
（分数：5.00）
A.Exercise and warming.
B.Warming and chilling.
C.Heat and cold.
D.Absorption and distribution.
A.Smelly.
B.Scattered.
C.Blocking doors and store shutters.
D.Put in bags and boxes
A.Most benign tumors needn"t be called to the attention of a physician.
B.People suffering from cancers were born with them.
C.The distinction between benign and malignant tumors is consequently always impossible
D.Some tumors change their nature in the course of years, after a period of benign growth.
A.The play will be performed at another location.
B.The woman didn"t intend to attend the play.
C.It isn"t possible to cancel the play.
D.The play was going to be performed outside.
A.She"d prefer to go to a different restaurant.
B.She"ll join the man for dinner.
C.She has been to the restaurant before.
D.The man should order spaghetti at the restaurant.
（分数：5.00）
A.She thought the furniture would be promptly bought.
B.She doesn"t remember how much the furniture cost.
C.They bought the furniture after considerable thought.
D.They bought the furniture on a credit basis.
A.She"d like to watch television with the man.
B.The man shouldn"t waste his time watching television.
C.The man should wash dishes.
D.The television program doesn"t start until later in the evening.
A.Help the woman repair her car.
B.Help the woman find a job.
C.Cancel the woman"s appointment for her.
D.Take the woman to her doctor"s office.
A.His housemate doesn"t want the windows closed.
B.His housemate is responsible for paying the electric bill.
C.The windows are hard to close.
D.He"s anxious for the weather to warm up.
A.A bridge to Manhattan.
B.Skyscrapers at dusk.
C.A lot of things in Manhattan.
D.A classical night view in Manhattan.
（分数：5.00）
A.He moved into his new apartment a couple of months ago.
B.He"d like the woman to help him pay the rent.
C.He and Peter have downloaded a new apartment.
D.The apartment might be too expensive for him.
A.The mirror is only half done.
B.They could take the mirror back to the store next week.
C.The mirror is on 50% discount.
D.Look for a bigger mirror on sale.
A.To order some medicine for the man.
B.To get something for Aunt"s birthday.
C.To buy some items.
D.To see some car models.
A.Try to switch hours with someone else.
B.Look before you leap.
C.There has to be a trade-off between job and pastime.
D.Do the extra work without complaining.
A.Roomy and comfortable.
B.Nice but expensive.
C.Cheap and comfortable.
D.Roomy but expensive.
三、Section B(总题数：0，分数：0.00)
四、Passage One(总题数：1，分数：5.00)
（分数：5.00）
A.Because he had felt severe pain on both sides of the abdomen.
B.Because he could not stand the intolerable pain in the back.
C.Because he had brought up what he had.
D.Because he has got diarrhea.
A.His time was fully occupied.
B.He had some urgent cases to deal with.
C.His boss asked him to do extra work.
D.Two tablets of analgesics killed his pain.
A.First in the fight abdomen and then it went to the lower abdomen.
B.First in the lower abdomen and then it shifted to the fight lower abdomen.
C.First in the left abdomen and then it shifted to the right lower abdomen.
D.First in the upper abdomen and then it shifted to the fight lower abdomen.
A.He has got acute appendicitis.
B.He has got acute diarrhea.
C.He has a duodenal ulcer.
D.He has got an acute gastric ulcer.
A.He will go through the formalities of admittance to hospital.
B.He will go to the operating room.
C.He will go to the outpatient department.
D.He will go to the inpatient department.
五、Passage Two(总题数：1，分数：5.00)
（分数：5.00）
A.Every child in hospital receives some teaching.
B.Not enough is known about hospital teaching.
C.Hospital teaching is of poor quality.
D.The special children"s hospitals are worst off.
A.Hospital teaching across the country is similar.
B.Each hospital has at least one part-time teacher.
C.All hospitals surveyed offer education to children.
D.Only one-fourth of the hospital has full-time teachers.
A.Hospital teachers.
B.Schoolmates.
C.Parents.
D.School teachers.
A.The author is unfavorable towards children receiving education in hospitals.
B.The author is in favor of the present state of teaching in hospitals.
C.The author is unsatisfied with the present state of hospital teaching.
D.The author is satisfied with the results of the latest survey.
A.Doctors and nurses.
B.Finding a hospital teacher.
C.The school teacher.
D.New medical instruments.
六、Passage Three(总题数：1，分数：5.00)
（分数：5.00）
A.How birds learn to build nests.
B.Why birds lay eggs.
C.How birds" nests have evolved.
D.Why some birds" nests are considered primitive.
A.Their flying ability improved greatly.
B.They became warm-blooded.
C.They began to lay eggs.
D.They changed their migration patterns.
A.On the ground.
B.In cold places.
C.On the highest branches of trees.
D.Inside tree trunks.
A.A primitive type of nest.
B.An elevated nest.
C.A typical cup-shaped nest.
D.A nest of twigs and branches.
A.To avoid predators.
B.To expose tile eggs to stronger sunlight.
C.To have a better view of predators.
D.To save labor.
七、PartⅡ Vocabulary(总题数：0，分数：0.00)
八、Section A(总题数：10，分数：5.00)
1.Already the class is ______ about who our new teacher will be.（分数：0.50）
A.foreseeing
B.speculating
C.fabricating
D.contemplating
2.For many patients, institutional care is the most ______ and beneficial form of care.（分数：
0.50）
A.pertinent
B.appropriate
C.acute
D.persistent
3.The automatic doors in supermarkets ______ the entry and exit of customers with shopping carts.（分数：0.50）
A.furnish
B.induce
C.facilitate
D.allocate
4.If you want this painkiller, you"ll have to ask the doctor for a ______.（分数：0.50）
A.inscription
B.transcription
C.description
D.prescription
5.The basic causes are unknown, although certain conditions that may lead to cancer have been ______.（分数：0.50）
A.identified
B.guaranteed
C.notified
D.conveyed
6.We should ______ all advanced science and technology to develop our economy.（分数：0.50）
A.draw on
B.draw in
C.draw up
D.draw out
7.There had been another prison breakout. Five men got away and are still ______.（分数：0.50）
A.in detail
B.at length
C.at large
D.at a loss
8.Helicopters rushed to where Shenzhou 5 ______ for the rescue of China"s first astronaut.（分数：0.50）
A.settled down
B.shot down
C.touched down
D.turned down
9.I can"t possibly mark your homework: your handwriting is ______. You must spend time in improving it.（分数：0.50）
A.illogical
B.illicit
C.illegible
D.illusive
10.The president gave a ______ for the visiting heads of the countries.（分数：0.50）
A.recession
B.reflection
C.recognition
九、Section B(总题数：10，分数：5.00)
11.The rosemary plant is an emblem of fidelity and remembrance.（分数：0.50）
A.thoughtfulness
B.tenderness
C.faithfulness
D.happiness
12.Proper exercise plays a significant role in the rehabilitation of patients with various back ailments.（分数：0.50）
A.equation
B.recovery
C.distress
D.relaxation
13.The patient who takes interest in everything and everybody is a formidable adversary for disease.（分数：0.50）
A.dreadful
B.principal
C.potential
D.imaginary
14.The scientists at the University of Bern in Switzerland have used a weakened virus that is not infectious and has proved safe and effective.（分数：0.50）
A.dangerous
B.harmful
C.contagious
D.invading
15.The doctor did not rule out the possibility of food poisoning.（分数：0.50）
A.include
B.exclude
C.foresee
D.question
16.In the final straight Meyers stumbled , and although he didn"t fall it was enough to lose his first place.（分数：0.50）
A.staggered
B.screamed
C.startled
D.rebuked
17.The coach explained the regulations at length to make sure that none of his players would become violators.（分数：0.50）
A.in general
B.at best
C.in detail
D.at last
18.The mental patient fluctuates between great excitement and deep depression.（分数：0.50）
A.stabilizes
B.recovers
C.worsens
D.alternates
19.Because he wore a strange collection of clothes and often talked to himself, his neighbor considered him eccentric .（分数：0.50）
B.energetic
C.exotic
D.peculiar
20.It is true that the alleged power of dreams to predict future events still remains unproved.（分数：0.50）
A.supposed
B.well-known
C.true
D.legal
十、PartⅢ Cloze(总题数：1，分数：10.00)
The injection that the girl had been given was beginning to work. Her head 1 heavy, and she was very sleepy. Once she opened her eyes and saw two nurses. They were placing her on another bed. Then she had the feeling of moving down a long hall. Once 2 a while, she thought that she heard people talking around her. The last time she opened her eyes, she saw a large round lamp above her. Then everything was dark, and she 3 into a deep sleep.
The doctor was 4 to begin. First he opened the chest 5 around the heart. Meanwhile, another doctor connected the special machine to her. Next, the first doctor used an electric shock to stop the girl"s heart. Working very carefully, he repaired the passage that was 6 . Then, using another electric shock, he 7 the heart again. He closed her chest, and the operation was 8 . No additional blood had been needed. The 9 operation lasted ninety minutes. The girl was taken to another room. She would be watched until she was conscious.
As she opened her eyes, the girl saw her mother"s face. Her mother smiled. "It"s all over," she said. "The doctor promised to make you better and he has succeeded. In a few weeks you"ll be 10 home."（分数：10.00）
A.felt
B.feel
C.became
D.turned
A.at
B.of
C.in
D.for
A.went
B.fell
C.got
D.became
A.sure
B.eager
C.ready
D.quick
A.area
B.field
C.point
D.portion
A.damaged
B.hurt
C.injured
D.wounded
B.began
C.started
D.ceased
A.over
B.up
C.all
D.off
A.full
B.all
C.entire
plete
A.sent
B.taken
ing
D.going
十一、PartⅣ Reading Compre(总题数：0，分数：0.00)
十二、Passage One(总题数：1，分数：5.00)
Women"s minds work differently from men"s. At least, that is what most men are convinced of. Psychologists view the subject either as a matter of frustration or a joke. Now the biologists have moved into this minefield, and some of them have found that there are real differences between the brains of men and women. But being different, they point out hurriedly, is not the same as being better or worse.
There is, however, a definite structural variation between the male and female brain. The difference is in a part of the brain that is used in the most complex intellectual processes —the link between the two halves of the brain.
The two halves are linked by a trunk line of between 200 and 300 million nerves, the corpus callosum (胼胝体). Scientists have found quite recently that the corpus callosum in women is always larger and probably richer in nerve fibers than it is in men. This is the first time that a structural difference has been found between the brains of women and men and it must have some significance. The question is "What?", and, if this difference exists, are there others? Research shows that present-day women think differently and behave differently from men. Are some of these differences biological and inborn, a result of evolution? We tend to think that is the influence of society that produces these differences. But could we be wrong?
Research showed that these two halves of the brain had different functions, and that the corpus callosum enabled them to work together. For most people, the left half is used for word-handing, analytical and logical activities; the right half works on pictures, patterns and forms. We need both halves working together. And the better the connections, the more harmoniously the two halves work. And, according to research findings, women have the better connections.
But it isn"t all that easy to explain the actual differences between skills of men and women on this basis. In schools throughout the world girls tend to be better than boys at "language subjects" and boys better at maths and physics. If these differences correspond with the differences in the hemispheric trunk line, there is an unalterable distinction between the sexes.
We shan"t know for a while, partly because we don"t know of any precise relationship between abilities in school subject and the functioning of the two halves of the brain, and we cannot understand how the two halves interact via the corpus callosum. But this striking difference must have some effect and, because the difference is in the parts of the brain involved in intellect, we should be looking for differences in intellectual processing.（分数：5.00）
(1).Which of the following statement is CORRECT?（分数：1.00）
A.Biologists are conducting research where psychologists have given up.
B.rain differences point to superiority of one sex over the other.
C.Results of scientific research fail to support popular belief.
D.The structural difference in the brain between the sexes has long been known.
(2).According to the passage it is commonly believed that brain differences are caused by ______ factors.（分数：1.00）
A.biological
B.psychological
C.physical
D.social
(3)."These differences" in paragraph 5 refer to those in ______.（分数：1.00）
A.skills of men and women
B.school subjects
C.the brain structure of men and women
D.activities carried out by the brain
(4).At the end of the passage the author proposes more work on ______.（分数：1.00）
A.the brain structure as a whole
B.the functioning of part of the brain
C.the distinction between the sexes
D.the effects of the corpus callosum
(5).What is the main purpose of the passage?（分数：1.00）
A.To outline the research findings on the brain structure.
B.To explain the link between sex and brain structure.
C.To discuss the various factors that cause brain differences.
D.To suggest new areas in brain research.
十三、Passage Two(总题数：1，分数：5.00)
Can electricity cause cancer? In a society that literally runs on electric power, the very idea seems preposterous. But for more than a decade, a growing band of scientists and journalists has pointed to studies that seem to link exposure to electromagnetic fields with increased risk of leukemia and other malignancies. The implications are unsettling, to say the least, since everyone comes into contact with such fields, which are generated by everything electrical, from power lines and antennas to personal computers and micro-wave ovens. Because evidence on the subject is inconclusive and often contradictory, it has been hard to decide whether concern about the health effects of electricity is legitimate—or the worst kind of paranoia.
Now the alarmists have gained some qualified support from the U.S. Environmental Protection Agency. In the executive summary of a new scientific review, released in draft form late last week, the EPA has put forward what amounts to the most serious government warning to date. The agency tentatively concludes that scientific evidence "suggests a casual link" between extremely
low-frequency electromagnetic fields—those having very longwave-lengths—and leukemia, lymphoma and brain cancer, While the report falls short of classifying ELF fields as probable carcinogens, it does identify the common 60-hertz magnetic field as "a possible, but not proven, cause of cancer in humans".
The report is no reason to panic—or even to lost sleep. If there is a cancer risk, it is a small one. The evidence is still so controversial that the draft stirred a great deal of debate within the Bush Administration, and the EPA released it over strong objections from the Pentagon and the White House. But now no one can deny that the issue must be taken seriously and that much more research is needed.
At the heart of the debate is a simple and well-understood physical phenomenon: When an electric current passes through a wire, it generates an electromagnetic field that exerts forces on
surrounding objects. For many years, scientists dismissed any suggestion that such forces might be harmful, primarily because they are so extraordinarily weak. The ELF magnetic field generated by a video terminal measures only a few milligauss, or about one-hundredth the strength of the earth"s own magnetic field. The electric fields surrounding a power line can be as high as 10 kilovolts per meter, but the corresponding field induced in human cells will be only about 1 millivolt per meter. This is far less than the electric fields that the cells themselves generate. How could such minuscule forces pose a health danger? The consensus used to be that they could not, and for decades scientists concentrated on more powerful kinds of radiation, like X-rays, that pack sufficient wallop to knock electrons out of the molecules that make up the human body. Such "ionizing" radiations have been clearly linked to increased cancer risks and there are regulations to control emissions.
But epidemiological studies, which find statistical associations between sets of data, do not prove cause and effect. Though there is a body of laboratory work showing that exposure to ELF fields can have biological effects on animal tissues, a mechanism by which those effects could lead to cancerous growths has never been found.
The Pentagon is far from persuaded. In a blistering 33-page critique of the EPA report, Air Force scientists charge its authors with having "biased the entire document" toward proving a link. "Our reviewers are convinced that there is no suggestion that electromagnetic fields present in the environment induce or promote cancer," the Air Force concludes. "It is astonishing that the EPA would lend its imprimatur on this report." Then Pentagon"s concern is understandable. There is hardly a unit of the modem military that does not depend on the heavy use of some kind of electronic equipment, from huge ground-based radar towers to the defense systems built into every warship and plane.（分数：5.00）
(1).The main idea of this passage is ______.（分数：1.00）
A.studies on the cause of cancer
B.controversial view-points in the cause of cancer
C.the relationship between electricity and cancer
D.different ideas about the effect of electricity on caner
(2).The view-point of the EPA is ______.（分数：1.00）
A.there is casual link between electricity and cancer
B.electricity really affects cancer
C.controversial
D.low frequency electromagnetic field is a possible cause of cancer
(3).Why did the Pentagon and White House object to the release of the report? Because ______.（分数：1.00）
A.it may stir a great deal of debate among the Bush Administration
B.every unit of the modem military has depended on the heavy use of some kind of electronic equipment
C.the Pentagon"s concern was understandable
D.they had different arguments
(4).It can be inferred from physical phenomenon ______.（分数：1.00）
A.the force of the electromagnetic field is too weak to be harmful
B.the force of the electromagnetic field is weaker than the electric field that the cells generate
C.electromagnetic field may affect health
D.only more powerful radiation can knock electron out of human body
(5).What do you think ordinary citizens may do after reading the different arguments?（分数：
1.00）
A.They are indifferent.
B.They are worried very much.
C.The may exercise prudent avoidance.
D.They are shocked.
十四、Passage Three(总题数：1，分数：5.00)
Here"s a familiar version of the boy-meets-girl situation. A young man has at last plucked up courage to invite a dazzling young lady out to dinner. She has accepted his invitation and he is overjoyed. He is determined to take her to the best restaurant in town, even if it means that he will have to live on memories and hopes during the month to come. When they get to the restaurant, he discovers that this ethereal creature is on a diet. She mustn"t eat this and she mustn"t eat that. Oh, but of course, she doesn"t want to spoil his enjoyment. Let him by all means eat as much fattening food as he wants: it"s the surest way to an early grave. They spend a truly memorable evening together and never see each other again.
What a miserable lot dieters are! You can always recognize them from the sour expression on their faces. They spend most of their time turning their noses up at food. They are forever consulting calorie charts; gazing at themselves in mirrors; and leaping on to weighing-machines in the bathroom. They spend a lifetime fighting a losing battle against spreading hips, protruding tummies and double chins. Some wage all-out war on FAT. Mere dieting is not enough. They exhaust themselves doing exercises, sweating in sauna baths, being pummeled and massaged by weird machines. The really wealthy diet-mongers pay vast sums for "health cures". For two weeks they can enter a nature clinic and be starved to death for a hundred guineas a week. Don"t think it"s only the middle-aged who go in for these fads either. Many of these bright young things you see are suffering from chronic malnutrition: they are living on nothing but air, water and the goodwill of God. Dieters undertake to starve themselves of their own free will; so why are they so miserable? Well, for one thing, they"re always hungry. You can"t be hungry and happy at the same time. All the horrible concoctions they eat instead of food leave them permanently dissatisfied. Wonderfood is a complete food, the advertisement says. Just dissolve a teaspoonful in water. A complete food it may be, but not quite as complete as a juicy steak. And, of course, they"re always miserable because they feel so guilty. Hunger just proves too much for them and in the end they lash out and devour five huge guilt-inducing cream cakes at a sitting. And who can blame them? At least three times a day they are exposed to temptation. What utter torture it is always watching others tucking into piles of mouth-watering food while you munch a water biscuit and sip unsweetened lemon juice!
What"s all this self-inflicted torture for? Saintly people deprive themselves of food to attain a state of grace. Unsaintly people do so to attain a state of misery. It will be a great day when all the dieters in the world abandon their slimming courses; when they hold out their plates and demand second helpings!（分数：5.00）
(1).The best title for this passage is ______.（分数：1.00）
A.On Fat
B.We Should All Grow Fat and Be Happy
C.Many Diseases Are Connected with Fat
D.Diet Deprives People of Normal Life
(2).Why do they never see each other again?（分数：1.00）
A.Because it is a memorable evening.
B.Because she lets him eat as much fattening food as he wants.
C.Because she does not eat this and drink that.
D.Because eating fattening food is the surest way to an early grave.
(3).What"s the meaning of "lot" in the first line of Paragraph 2?（分数：1.00）
A.Amount.
B.Field.
C.Fate.
D.Group.
(4).Which of the following ways is NOT mentioned for diet?（分数：1.00）
A.Doing exercises.
B.Not eating sugar.
C.Not eating fat.
D.Taking sauna baths.
(5).What is the author"s attitude toward diet?（分数：1.00）
A.Persuasive.
B.Critical.
C.Indifferent.
D.Adversative.
十五、Passage Four(总题数：1，分数：5.00)
Educators are seriously concerned about the high rate of dropouts among the doctor of philosophy candidates and the consequent loss of talent to a nation in need of PhDs. Some have placed the dropouts loss as high as 50 percent. The extent of the loss was, however, largely a matter of expert guessing. Last week a well-rounded study was published. It was based on 22,000 questionnaires sent to former graduate students who were enrolled in 24 universities and it seemed to show many past fears to be groundless.
The dropouts rate was found to be 31 per cent, and in most cases the dropouts, while not completing the Ph.D. requirement, went on to productive work. They are not only doing well financially, but, according to the report, are not far below the income levels of those who went on to complete their doctorates.
Discussing the study last week, Dr. Tucker said the project was initiated because of the concern frequently expressed by graduate faculties and administrators that some of the individuals who dropped out of Ph.D. programs were capable of competing the requirement for the degree. Attrition at the Ph.D. level is also thought to be a waste of precious faculty time and a drain on university resources already being used to capacity. Some people expressed the opinion that the shortage of highly trained specialists and college teachers could be reduced by persuading the dropouts to return to graduate schools to complete the Ph.D. "The results of our research," Dr. Tucker concluded, "did not support these opinions."
1. Lack of motivation was the principal reason for dropping out.
2. Most dropouts went as far in their doctoral program as was consistent with their levels of ability or their specialities.
3. Most dropouts are now engaged in work consistent with their education and motivation. Nearly 75 per cent of the dropouts said there was no academic reason for their decision, but those who mentioned academic reason cited failure to pass the qualifying examination, uncompleted research and failure to pass language exams. Among the single most important personal reasons identified by dropouts for non-completion of their Ph.D. program, lack of finances was marked by 19 per cent.
As an indication of how well the dropouts were doing, a chart showed 2% in humanities were receiving $20,000 and more annually while none of the Ph. D."s with that background reached this figure. The Ph. D."s shone in the $7,500 to $15,000 bracket with 78% at that level against 50% for the dropouts. This may also be an indication of the fact that top salaries in the academic fields, where Ph. D."s tend to rise to the highest salaries, are still lagging behind other fields. As to the possibility of getting dropouts back on campus, the outlook was glum. The main condition which would have to prevail for at least 25% of the dropouts who might consider returning to graduate school would be to guarantee that they would retain their present level of income and in some cases their present job.（分数：5.00）
(1).The author states that many educators feel that ______.（分数：1.00）
A.steps should be taken to get the dropouts back to campus
B.the dropouts should return to a lower quality school to continue their study
C.the Ph.
D. holder is generally a better adjusted person than the dropout
D.the high dropouts rate is largely attributable to the lack of stimulation on the part of faculty members
(2).Research has shown that ______.（分数：1.00）
A.dropouts are substantially below Ph. D."s in financial attainment
B.the incentive factor is a minor one in regard to pursuing Ph.D. studies
C.the Ph.
D. candidate is likely to change his field of specialization if he drops out
D.about one-third of those who start Ph.D. work do not complete the work to earn the degree
(3).Meeting foreign language requirements for the Ph. D. ______.（分数：1.00）
A.is the most frequent reason for dropping out
B.is more difficult for the science candidate than for the humanities candidate
C.is an essential part of many Ph.
D. programs
D.does not vary in difficulty among universities
(4).After reading the article, one would refrain from concluding that ______.（分数：1.00）
A.optimism reigns in regard to getting Ph. D. dropouts to return to their pursuit of the degree
B.a Ph.D. dropout, by and large, does not have what it takes to learn the degree
C.colleges and universities employ a substantial number of Ph. Ｄ. dropouts
D.Ph. Ｄ."s are not earning what they deserve in nonacademic positions
(5).It can be inferred that the high rate of dropouts lies in ______.（分数：1.00）
A.salary for Ph.D. too low
B.academic requirement too high
C.salary for dropouts too high
D.1,000 positions
十六、Passage Five(总题数：1，分数：5.00)
Avian influenza is an infectious disease of birds caused by type A strains of the influenza virus. The disease, which was first identified in Italy more than 100 years ago, occurs worldwide. All birds are thought to be susceptible to infection with avian influenza, though some species are more resistant to infection than others. Infection causes a wide spectrum of symptoms in birds, ranging from mild illness to a highly contagious and rapidly fatal disease resulting in severe epidemics. The latter is known as "highly pathogenic avian influenza". This form is characterized by sudden onset, severe illness, and rapid death, with a mortality that can approach 100%. Fifteen subtypes of influenza virus are known to infect birds, thus providing an extensive reservoir of influenza viruses potentially circulating in bird populations. To date, all outbreaks of the highly pathogenic form have been caused by influenza A viruses of subtypes H5 and H7. Migratory waterfowl—most notably wild ducks—are the natural reservoir of avian influenza viruses, and these birds are also the most resistant to infection. Domestic poultry, including chickens and turkeys, are particularly susceptible to epidemics of rapidly fatal influenza. Direct or indirect contact of domestic flocks with wild migratory waterfowl has been implicated as a frequent cause of epidemics. Live bird markets have also played an important role in the spread of epidemics.
Recent research has shown that viruses of low pathogenicity can, after circulation for sometimes short periods in a poultry population, mutate into highly pathogenic viruses. During a 1983-1984 epidemic in the United States of America, the H5N2 virus initially caused low mortality, but within six months became highly pathogenic, with a mortality approaching 90%. Control of the outbreak required destruction of more than 17 million birds at a cost of nearly US$ 65 million. During a 1999-2001 epidemic in Italy, the H7N1 virus, initially of low pathogenicity, mutated within。