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1、Visit www.readinga- for thousands of books and materials.InFLUenzaA Reading AZ Level W Leveled BookWord Count:1,860www.readinga-LEVELED BOOK WTWZWritten by Ned JensenInFLUenzaWritten by Ned Jensenwww.readinga-InFLUenza24mutating(v.)changing into a different form(p.9)pandemic(n.)the rapid,worldwide s
2、pread of a disease(p.19)parasites(n.)organisms that grow in and feed off other organisms(p.6)protein(n.)an essential nutrient found in the cells of all living things (p.5)respiratory the passages in the nose,tract(n.)mouth,throat,and lungs through which air travels during breathing(p.7)strain(n.)a g
3、roup of microbes of the same type(p.9)submicroscopic too small to be seen with an (adj.)ordinary microscope(p.5)vaccines(n.)medicines made of weak or dead viral strains that teach the body to fight stronger viruses of the same type(p.13)virus(n.)a microorganism that infects the body;a disease caused
4、 by a virus(p.5)2423Glossaryantibodies(n.)chemicals produced by the body that attack invading germs(p.11)congested(adj.)filled up or blocked(as with mucus in the nose and throat)(p.7)contagious(adj.)able to spread from one organism to another(p.12)epidemic(n.)the rapid spread of a disease within a c
5、ommunity(p.18)exposure(n.)unprotected contact with something harmful(p.12)genetic the part of a cell that carries material(n.)the basic information about an organisms characteristics(p.5)germs(n.)microorganisms that often cause sickness or disease(p.4)hosts(n.)organisms in or on which another organi
6、sm lives(p.6)invasive(adj.)relating to moving into a new area or body with harmful or disruptive effects(p.11)microbe(n.)See microorganism(p.5)microorganism a microscopic organism,such (n.)as a virus or single bacterial cell(p.5)InFLUenza Level WInFLUenzaLevel W Leveled Book Learning AZWritten by Ne
7、d JensenIllustrated by Cende HillAll rights reserved.www.readinga-Photo Credits:Front cover:iS Perkins;back cover:Santos06/D;title page:iS Wilson;pages 3,8:courtesy of James Gathany/CDC;page 4:Photodisc/C Squared Studios/Getty Images;page 5:courtesy of Cynthia Goldsmith/CDC;pages 7,10(top left,botto
8、m left,center bottom),12,13,15(top,second-left,second-right,seventh),22:Jupiterimages Corporation;page 9(top):iS Martin;page 9(bottom):iS Campbell;page 10(right):iS Davis;page 15(third):iS Marx;page 15(fourth):iS Romanenko;page 15(fifth):iS Young;page 15(sixth):iS Bloom;page 16:REUTERS/Nacho Doce;pa
9、ge 17(top left):iS Dongel;page 17(top right):Evan66/D;page 17(bottom left):iS 17(bottom right):iS Smokovski;page 18:courtesy of Library of Congress,Prints&Photographs Div LC-USF34-039530-D;page 19:courtesy of Knowland Collection/Oakland,CA Public Library/Edward A Rogers;page 21:REUTERS/Beawiharta EN
10、/RCSCorrelationLEVEL WS4040Fountas&PinnellReading RecoveryDRA233Table of ContentsIntroduction.4What Is the Flu?.5Changing Viruses .9The Body Fights Back.11Preventing the Virus from Taking Over.12Treating the Flu .17History of the Flu .18Conclusion .22Glossary .23InFLUenza Level W22ConclusionBecause
11、flu viruses can change and develop into new strains,influenza may never be eradicated.When you have the flu,the most important thing to do is take care of yourself and prevent others from getting sick.Keep your germs to yourself by staying away from other people and covering your nose and mouth when
12、 you cough or sneeze.Drink water like a thirsty camel and sleep like a hibernating bear.Getting a flu vaccine each year can also help.Most importantly,remember to attack back!Good food and rest will help the healthy cells in your body win the battle.4IntroductionHave you ever shivered with chills or
13、 burned up with a fever?Have you ever had a sore throat,a stuffy nose,a pounding headache,and muscle aches?Have you ever felt really tired and sleepy,even though youve just woken up in the morning?If you feel symptoms such as these,flu germs may have invaded your body.By learning about the fluwhat i
14、t is,what causes it,what its symptoms are,and how to treat ityou can fight back against this illness and stay healthy.A water bottle and a blanket can help when you have the flu.21Other outbreaks have caused widespread concern without developing into pandemics.These include the Russian flu in 1977 a
15、nd the avian flu in 1997 and 1999.Both of these strains of flu began in regions of China and spread to other countries.Doctors are always on the lookout for the next major outbreak.They believe that if they can detect outbreaks quickly enough,they can keep them from becoming worldwide pandemics.Mask
16、s that fit around the nose and mouth are sometimes worn to help prevent the spread of viruses.However,the masks do not work all the time.InFLUenza Level W5What Is the Flu?The flu is also called influenza(in-floo-EN-zah).Its caused by a virus that has the ability to quickly spread between people.A vi
17、rus is a tiny microorganisma microbe,or germthat is invisible to the naked eye.Very simply,a virus is a little bit of genetic material surrounded by a hard protein shell that protects it.Viruses are submicroscopicso small that scientists must use powerful microscopes to see them.Even when viewed thr
18、ough a microscope,a virus can only be seen after its image has been magnified to one thousand times its original size.In fact,viruses are so small that hundreds of thousands of them can live on the head of a pin.Viruses are everywhere.Some wont bother you at all,but some can be dangerous to people a
19、nd other animals.During flu season,which lasts from October to May in the northern hemisphere,viruses are particularly widespread.Like many other organisms,viruses need a particular type of home.Viruses survive by making their homes inside animals.Avian influenza virusInFLUenza Level W20But the pand
20、emic of 1918 was not the only major influenza outbreak in history.The Asian flu,which appeared in 1957,caused about 70,000 deaths in the United States.It got its name because it first appeared in China before coming to the United States in June 1957.Another strain of flu,the Hong Kong flu,was first
21、detected in Hong Kong,China.In 1968,this virus caused another pandemic,resulting in 34,000 deaths in just the United Statesas many people as live in a small city.And in 2009,the H1N1 swine flu became the first pandemic in 41 years,infecting people in over 70 countries.This map shows an example of ho
22、w pandemics,such as the Asian flu of 19571958,might spread from one area to many others.ChinaJapanPACIFIC OCEANIndiaRussiaMongolia6How a virus spreads in the bodyA virus invades a cell in a human body.The virus takes over the cell and makes copies of itself.Copies of the virus break out of the cell
23、and start invading other cells.12Viruses act like parasites in your cells.Although they can survive for long periods on their own,they must eventually find organisms to serve as hosts.Viruses use the cells of the hosts to reproduce.When a virus infects a human being,it uses its hard protein shell to
24、 make a hole in a cell,which it then invades.Once inside a cell,the virus rapidly makes copies of itself.One to four days after infection,the host may begin to feel sick.Influenza is spread through the passing of viruses from one person to another.For this reason,it is always important to wash your
25、hands and to cover your mouth when you cough or sneeze.If you are infected,it is important that you stay home,away from other people,so you dont spread your germs.319The history of any influenza outbreak begins with a single person.On March 11,1918,a young man in the U.S.Army reported to a hospital
26、with a fever,sore throat,and a headache.Shortly after,many other soldiers at his base developed the same symptoms.In one week,the Army hospital was treating more than five hundred sick soldiers.By the end of spring,forty-eight of those people had died.At first,no one knew why,not even the doctors an
27、d scientists.Doctors later learned that the illness was caused by a particular strain of the influenza virus.In total,this strain of influenza,known as the Spanish flu,killed more than 600,000 Americans and 25 to 40 million people worldwide.When an outbreak reaches this size,it is known as a pandemi
28、ca disease that spreads rapidly around the world.1918 Spanish flu patientsInFLUenza Level W7Different viruses cause the many different kinds of flu,but the symptoms are similar.Influenza is an infection of the respiratory tract that usually causes you to feel achy,feverish,congested,sick to your sto
29、mach,and worn down.Flu viruses attack the respiratory tract.lungsmouthnosepharynxwindpipe(trachea)larynxInFLUenza Level W18History of the FluMany outbreaks of influenza have occurred throughout history.Some of them have been mild and not very widespread.Other outbreaks have been severe,spreading thr
30、oughout the world and killing millions of people.Once a flu virus develops and infects a few people,it can spread rapidly and become an epidemic.Flu epidemics have been recorded as far back as four hundred years ago,and each has killed thousands of people or more.A doctor gives children shots of vac
31、cine in 1941.8Influenza has three basic types:Influenza A,Influenza B,and Influenza C.Influenza A,which can cause serious illness in humans and other animals,is usually responsible for large outbreaks.Influenza B is milder,causes smaller outbreaks,and affects only humans(mostly children).Influenza C
32、 usually causes only mild illness in humans.Tiny drops of saliva and mucus fill the air when you sneeze.All types of influenza can be passed from an infected person to a healthy person through the air or on objects such as eating and drinking utensils.The flu virus is carried in saliva from an infec
33、ted persons mouth and on droplets of mucus sneezed or coughed into the air.17Treating the FluPreventing the flu is not always possible.However,once viruses infect your body,you can still do several things to fight back.Pharmacies offer many over-the-counter medicines that can help relieve the effect
34、s of the flu.These medicines can take away the achy feeling in your head and muscles.They can also help reduce a fever.Drinking plenty of fluids,such as water or fruit juices,is also important when you have the flu.You should also get plenty of rest so your body can better fight the viruses that hav
35、e invaded your cells.InFLUenza Level W9Changing VirusesViruses are capable of changing,or mutating,and flu viruses are among the most changeable of all viruses.Each type of virus that mutates from another virus is called a strain of that virus.Many influenza viruses start in wild animals,most often
36、in birds.These viruses can easily mutate into strains that infect ducks and chickens on farms.Once a virus has infected birds on farms,it can further mutate into strains that infect animals such as pigs,and even humans.Wild birds(above)often pass viruses to farm chickens(right),which come into more
37、contact with people.InFLUenza Level W16Do You Know?I bet you didnt know that many vaccines are made in hundreds of millions of specially grown chicken eggs!Can you imagine that many eggs?They would fill up about fifty football fields.Scientists and doctors begin by separating viruses to isolate the
38、selected virus.Then,as you might expect,they kill or weaken the virus and combine it with two other dead virus strains that have been similarly grown in chicken eggs.Then they combine the dead and weakened viruses to make a vaccine to protect you from each strain.10The chain of animals infected vari
39、es from virus to virus.A single virus chain may include animals as different as dogs and whales.Since chickens,pigs,and humans come in close contact on farms,the spreading and mixing of viruses can have deadly consequences.Sometimes a virus takes a shortcut in the chain,such as the avian virus of 19
40、97,which jumped directly from birds to humans.Influenza can pose a serious threat to humans.Even if your body fights off the illness,the virus can mutate into a different strain.Then your body must start all over again,learning how to fight the new strain.Scientists always worry that the next new st
41、rain will be even more deadly than previous ones.A sample virus chainwild duckpigchickenhuman15High-Risk PopulationsPeople over 65Babies and very young childrenPregnant womenPeople with diabetesPeople with heart and lung diseasePeople who are sick and exhaustedHealthcare workersInFLUenza Level W11Th
42、e Body Fights BackThe human body has ways of fighting back against an invasion of flu viruses.The immune system protects against the invasion of harmful microbes by producing chemicals called antibodies,which travel in the blood and patrol the body in search of invaders.When they find an invasive mi
43、crobe,antibodies attack and destroy any cells that contain the virus.However,if the immune system of a human body invaded by a virus is already weak,viruses can gain a foothold and begin reproducing themselves faster than antibodies are able to destroy them.When this happens,the body comes down with
44、 flu symptoms that quickly get worse without medical care.white blood cellsantibodiesvirusescell infected with flu virusInFLUenza Level W14Each strain of a virus requires a different vaccine.Some flu vaccines contain several strains.When these strains are injected into the body,each one causes the b
45、ody to produce a particular antibody to destroy it.In this way,the body is prepared to defend against many strains of viruses that doctors think might be present during flu season.Vaccines for most viral strains have an eighty-percent prevention rate,which means that eighty percent of the time,you w
46、ont get sick from a strain you have been vaccinated against.Thats pretty high,but its not perfect,so you might still get the flu even if youve been vaccinated.But if youve had the vaccine,your symptoms will be milderyou wont ache so much,and you wont feel so hot.However,if you are infected with a st
47、rain different from those in your flu shot,you can still get very sick.Scientists must be good detectives to guess which strains to put into the flu shot each year.Not everyone has the same risk of catching the flu,and some people get more seriously ill than others.People who are very young or very
48、old,or who already have health conditions such as diabetes and heart disease,are at greater risk of catching the flu than others.13However,even the most cautious people can become infected.Fortunately,medical scientists have found a way to keep the flu virus from taking over your body:vaccines.Vacci
49、nes are weakened or dead flu viruses that are injected into a persons body.These weakened viruses cause the body to produce antibodies that attack and destroy the weakened or dead germs.Once the body has produced antibodies to destroy the viruses in the vaccine,it is on alert and prepared to attack
50、stronger viruses that may invade during flu season.Scientists study ways to help your body fight the flu.InFLUenza Level W12Preventing the Virus from Taking OverYou can take some commonsense actions to prevent a flu virus from entering your body.Two of the best ways to stay healthy are by getting pl