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Then and now

As you can see, things are a lotbetter than they used to be—atleast for most people in theUnited States and other industri-alized countries. Of course, theworld is far from perfect. Butmany of the health problems weface today are relatively minorcompared with those of ourancestors. What’s more, whenfaced with serious health chal-lenges, we have a lot more powerto fight against them than weused to have. We can cure manydiseases that once killed peopleby the dozens, and althoughsome new diseases (such asAIDS) have emerged that cannotbe cured, in many cases weunderstand at least how thesediseases are transmitted andhow they can be prevented. In fact, it would be reasonable to argue that we have gainedmore power over our health inthe past 150 years than we did in the thousand years prior tothat period.

What happened over the last 150years that has brought us to thisnew place in human history? The next section will providesome answers to this importantquestion.

THE FIGHT AGAINST CONTAGIOUS DISEASES

Understanding the role of germs

Many kinds of ill-nesses are causedby microbes—tiny life-forms that aretoo small to be seenwith the naked eye.There are manykinds of microbes,including bacteria,protozoa, andfungi. Bacteria aresimple one-celledcreatures. Twokinds of bacteriaare Salmonella, a commoncause of food poisoning, andStreptococcus, the cause of

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Microbes aretiny life-formsthat can causeillnesses.

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“strep” throat. Protozoa are alsoone-celled creatures, but unlikebacteria, protozoa have a nucleusinside them. In this way, they aremore like animals or people thanthey are like bacteria. Protozoaare known to cause only a fewhuman diseases, of which two ofthe most common are malariaand dysentery. Fungi can growon or in the body and live bybreaking down dead cells or bodyfluids. Examples of common fun-gal infections include athlete’sfoot and yeast infections. Fungalinfections can also occur insidethe lungs. People with weakenedimmune systems, including elder-ly people and patients with AIDS,are especially vulnerable to somekinds of fungal infections.

Some scientists say that microbesinclude viruses, which causemany human diseases, from thecommon cold to AIDS. Viruses areextremely simple life-forms—sosimple that many scientists arguethat they are not life-forms at all.Others put them in a class bythemselves, somewhere betweenliving and nonliving things. Forthe purposes of this book, it iseasier to lump viruses in withmicrobes.

The world is full of microbes, andso is your body. A great many ofthem are harmless to people.Some are even helpful. (For exam-

Viruses: Living, Nonliving, or in Between?

Is a dog or a cat a living thing? Sure. A tree? Absolutely. A rock? Of course not.

But a virus? That’s a much trickier question.

Viruses—which cause illnesses and conditions such as thecommon cold, influenza, herpes, and rabies—are unlike livingthings in several important ways. First of all, they do not evenhave a single cell—the basic building block of life. Instead,they are mostly a strand of genetic material curled up insidea tiny bag made of protein. Second, viruses cannot grow orreproduce on their own.

Viruses also can’t take in energy: Unlike animals, they don’teat, and unlike plants, they don’t use sunlight to make theirown food. They can’t move on their own, so they have to becarried along in air, water, food, or body fluids, or passedaround from one surface to another.

However, viruses do share some characteristics with livingthings. They contain DNA (or a similar chemical called RNA),the genetic code for life. They can reproduce with the help ofa living cell. (They do this by injecting their DNA into the celland “hijacking” the cell’s own reproductive system, forcing itto make new viruses.) And over time, they can evolve—forexample, by developing a resistance to a drug. Some virusesthat cause human diseases are rhinoviruses, which causecolds; herpesviruses, which can cause cold sores and blisters;and the human immunodeficiency virus (HIV), whichcauses AIDS.

Some scientists classifyviruses as livingthings. Others classifythem as non-living.Still others believethat they belong totheir own unique category. But even if they’re not alivethemselves, virusesdefinitely play a bigrole in life on Earth.

Smallpox virus

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ple, the bacteria in your intes-tines help you digest food.) Butother microbes have the poten-tial to cause illness in thehuman body. We call these dis-ease-causing microbes germs.Germs can be spread throughfood, water, the air, or the envi-ronment. They can also bespread by physical contactbetween two people. Sometimesgerms can be spread by physicalcontact with animals, althoughmany germs that infect animalsare slightly different from theones that make people sick.

Before people knew about germs,they didn’t understand how dis-eases started and spread.

Sometimes they blamed diseaseson evil spirits—or, later, on “badblood,” an idea without any med-ical source. They would come upwith treatments based on theseideas, such as performing exor-cisms or deliberately cutting peo-ple to drain the “bad” blood.These treatments often failed,and even when they worked, doc-tors didn’t fully understand why.For example, garlic was used formedical purposes in manyancient cultures, but only recent-ly have scientists discovered thatit can kill germs.

One of the earliest known sug-gestions that germs cause dis-ease came from the Italian

Garlic haslong beenused to fightoff illness, but it is onlyrecently thatscientistslearned it can killgerms.

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physician Girolamo Fracastoro inthe year 1546. But his idea didn’tcatch on. For one thing, nobodycould see these germs—the micro-scope hadn’t been invented yet!And by the time scientists finallybegan to study bacteria and virus-es, Fracastoro’s work had beenmostly forgotten.

The “germ theory” of disease wasreally popularized by the Frenchchemist Louis Pasteur in the 19thcentury. By then, Pasteur was ableto show that the presence of germswas linked to certain illnesses.Once this idea was established,scientists started identifying thebacteria and viruses that causecommon diseases. As technologyimproved, so did our ability tofind, categorize, and study thesemicroscopic creatures.

Today, scientists have identifiedmany of the germs that causeknown human diseases—even theones that we can’t cure. Obviously,knowing what causes an illness isincredibly important to doctorsand patients who are trying tofight it, and scientists are workingvery hard to figure out the natureof more illnesses—like multiplesclerosis—so they can identifyand help eliminate the virusesthat may cause them.

LOUIS PASTEUR

Louis Pasteur (1822–1895), aFrench chemist, was one ofthe most important scien-tists in history. Many of hisaccomplishments andinsights set the stage formodern medicine.

Pasteur increased ourunderstanding of disease byproving the theory of spon-taneous generation—thebelief that some life-forms,such as insects andmicrobes, could suddenlymaterialize from nonlivingmatter—wasn’t true. Forexample, it was thoughtthat the mold that grew onspoiled milk just appearedthere from nothing.

People had believed inspontaneous generationsince ancient times, andalthough others beforePasteur had raised objec-

tions, Pasteur’s experiments were the most convincing. Heproved that molds, fungi, and bacteria were actually present inthe air and that they wouldn’t grow on anything they couldn’ttouch.

Not only did Pasteur show that germs were present every-where, but he also pioneered ways to get rid of them. Heproved that boiling liquids like wine and milk killed any germsthat were present, and then he demonstrated that quickly seal-ing them off from air kept new germs from growing. Thisprocess is called pasteurization, and it’s still used today. Healso suggested that surgeons boil their instruments beforedoing surgery, but the idea didn’t catch on until later.

Pasteur’s work helped to convince other scientists that germswere the cause of contagious diseases. Among his manyaccomplishments, Pasteur pioneered vaccines for chicken pox,cholera, diphtheria, anthrax, and rabies.

Curbing the spread of disease

Once people came to understandthat germs cause many diseases,they started identifying andblocking the paths along whichthe germs travel. In many cases,doing this was possible beforeanyone had any detailed knowl-edge of the actual germs involved.

One strategy for blocking thespread of infectious disease isquarantine, which involves iden-tifying the people who have a con-tagious disease and separatingthem from healthy people so thatthe disease doesn’t spread.Quarantines have been used forthousands of years. More recently,

quarantines have helped controldiseases like the supercontagiousand deadly Ebola virus, whichhas devastated several villages inAfrica over the past few decades,and SARS (severe acute respira-tory syndrome).

Quarantines can be effective incontrolling some contagious dis-eases. But there are several bigdrawbacks. For one thing, it canbe hard to identify all the sickpeople. In many cases, a personmight be infected and still be ableto spread the disease for quite awhile before developing anysymptoms of the disease.Second, some infected peoplenever get sick at all. But in eithercase, a person who looks healthy

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A woman in Hong Kong wearsa mask to avoidbreathing in theSARS virus, whichis passed on byclose person-to-person contact.Using quarantineshelped to containthe disease in2003.

might still be able to pass on his or her germs to others. Quaran-tines also can’t always block otherways that germs might spread—for example, through infectedwater, food, animals, or insects.Finally, quarantines can mean sep-arating sick people from their jobs,friends, and family, and that canbe very hard to do. Today, bigquarantines involving lots of people are rare and are used mainly in emergencies.

Another way to control the spreadof disease is by controlling thevectors that help it spread. A vec-tor is a kind of middleman: a crea-ture which carries a germ thatinfects people. For example, mos-quitoes are the main vectors formalaria (a deadly disease commonin the tropics). For centuries,European explorers assumed thatthe disease was caused by some-thing in the tropical air (in fact,the word “malaria” translates to

“bad air”). But in 1895, the Britishbiologist Ronald Ross discoveredthat a tiny parasite (an organismthat lives off another organism)really causes the disease. Threeyears later, a team of Italian scien-tists figured out that the parasitewas carried by mosquitoes andwas spread through their bites.Once people understood this, peo-ple in tropical cities were able toreduce the threat of malaria bydraining nearby swamps wheremosquitoes bred.

The spread of disease can also becontrolled through sanitation—in other words, keeping our food,water, and environment clean.Many diseases, including choleraand typhoid fever, which havekilled countless people throughouthistory, are spread through infect-

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Mosquitos arethe main vectorsfor malaria,which is causedby a parasitespread throughtheir bites.

Using antiseptics and sterile tools and roomshelp make surgery safer than it once was.

ed drinking water. Other germsand parasites spread throughfood that’s unclean, spoiled, orimproperly cooked. Over the pastcentury, humans have learned alot about preparing and storingfood safely and treating publicwater supplies, and the healthpayoff has been extraordinary.

Surgery, dentistry, and medicinehave also been made much safer,thanks to the use of antiseptics(chemicals that kill germs).Antiseptics are used to make adoctor’s tools sterile (germfree).Before antiseptics became popu-lar, many patients died frominfections that were spread onunclean surgical instruments. Insome cases, having surgery wasactually more dangerous thanthe disease itself!

Even the simple practice ofwashing one’s hands has madean enormous difference in theoverall health of the public, sinceit keeps germs from spreading toeverything—and everyone—aperson touches. Frequent handwashing has become a wide-spread practice only within thepast century or so. While it’sespecially important for healthcare workers and food preparers,all people can benefit from wash-ing their hands on a regularbasis.

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JOSEPH LISTER

By the middle of the19th century, surgeonshad become fairlyskilled at their craft.However, even thoughthe operations them-selves went well, half ofthe patients died in thedays or weeks after sur-gery. The cause was usu-ally some kind ofinflammation aroundthe surgical wounds.Nobody quite knewwhat caused it. Somepeople thought it was akind of chemical reac-tion between openwounds and the oxygenin the air.

British surgeon JosephLister (1827–1912) had adifferent idea. He

believed that the inflammations were caused, not by the airitself, but by some kind of particle carried in it. When he heardabout Louis Pasteur’s research, he connected it to his ownobservations. He became convinced that the wounds werebeing infected by germs that lived in the air.

The problem now was how to get rid of the germs. He hadalready tried cleaning the wounds, with little success. Finally, heused a chemical called carbolic acid, which had been used totreat sewage in a nearby town. After he began cleaning hispatients’ wounds with carbolic acid, they remained free ofinfections.

Many people didn’t trust Lister’s techniques at first, but withina few decades they had caught on. In 1878, his work inspiredthe German surgeon Robert Koch to sterilize his surgical toolswith steam.

Today, surgery is conducted under antiseptic conditions, whichmeans that everything possible is done to keep the patient andthe surgical tools free of germs. Without antiseptic surgery,even the simplest operation would still be a very dangerousgamble.

The role of antibiotics and vaccines

The last century also saw a revolu-tion in the tools that we haveavailable to fight contagious dis-eases. Two of the most importantare antibiotics and vaccines.

Antibiotics are a class of drugsthat kill germs (usually bacteria)that are in your body. Antibioticscome in many forms: pills or liq-uids that you swallow, powerful

solutions that a doctor can injectwith a needle, and lotions, liquids,and creams that can be applied toyour skin or an open wound. Thereare many different kinds of antibi-otics; each one works best againstonly certain kinds of germs.

Doctors had long searched forways to fight disease-causinggerms directly, rather than justtreating the symptoms of the ill-ness. By the early 20th century,several possibilities were beingexplored, including sulfa drugs,which fight bacteria by blocking achemical they need in order toreproduce. Sulfa drugs were effec-tive against some infections, butweak or useless against others.Another potential treatment wasbacteriophage therapy.Bacteriophages are viruses thatkill harmful bacteria. To fight aninfection, doctors would inject bac-teriophages into a patient’s blood-stream. But because each kind ofbacteriophage kills only certainbacteria, the treatments were verylimited.

The first effective antibiotic wasdiscovered, partly by accident, bythe Scottish biologist AlexanderFleming, who was searching forsomething to fight bacteria, whichhe studied in little culture plates.Fleming also wasn’t the neatestperson in the world, and one day

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Washing your hands is an easy way to prevent the spread of germs.

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he came back from a long vaca-tion to find that some of his cul-ture plates had gotten moldy.Like countless scientists beforehim, Fleming threw the moldyplates away. But a former col-league, who happened to be visit-ing Fleming’s lab, saved some ofthe plates and noticed somethinginteresting: No bacteria weregrowing near the patches of mold.He pointed this out to Fleming,who did some more experimentsand isolated a bacteria-killingchemical from the mold that hecalled penicillin.

Fleming published his results in ajournal, or scientific magazine,and suggested that penicillinmight be useful if it could bemass produced. More than adecade would pass before anotherscientist, Howard Florey, devel-oped a technique for making peni-cillin in large quantities.

Penicillin became a “break-through drug,” because it wascheap to make, was generallysafe, and worked against a widevariety of infections. It is stillused today all over the world.Many more antibiotics were dis-covered because of it, and, by themiddle of the 20th century, antibi-otics had become the treatment ofchoice for diseases caused byinfections. It is no exaggeration tosay that millions of people are

alive today only because theyreceived antibiotics at some pointin their lives.

Another important weaponagainst contagious diseases is theuse of vaccines. Vaccines are dif-ferent from antibiotics, becausethey prevent disease rather thantreat it. Vaccines work by stimu-

ALLERGIES TO ANTIBIOTICS

Not all antibiotics are right for everyone. Some peoplehave allergies to certain antibiotics. For example,about 2 to 5 percent of Americans are allergic to penicillin, one of the most common and inexpensiveantibiotics. People can have allergies to other antibi-otics as well.

Allergic reactions to antibiotics range from mild rash-es to severe hives, tight airways, and difficulty breath-ing. In some cases, an allergic reaction can be deadly.

However, many unpleasant reactions to antibiotics—such as nausea, rashes, and diarrhea —are not reallyallergies, only side effects. For example, penicillin anddrugs like it can sometimes cause fever, itching, hives,or joint pain. Side effects of more powerful antibioticslike ciprofloxacin (which was used to treat peopleexposed to anthrax in the fall of 2001) include diar-rhea, drowsiness, strange dreams, and blurry vision.Most side effects are uncomfortable, but not lifethreatening. Also, people sometimes mistake thesymptoms of their illness for a reaction to an antibiot-ic. They may stop taking the antibiotic because theyfeel sick, when in fact the antibiotic is their bestchance to feel better. In fact, recent studies suggestthat 80 percent of people who believe they are aller-gic to penicillin are not really allergic at all.

If you’re not sure if you’re allergic to penicillin orany other antibiotic, ask your doctor. A simple skintest can give you the answer. If you are allergic, it’simportant to mention this whenever you get a newprescription or medical treatment. Usually, anotherantibiotic will be available for you.

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lating your immune system (yourbody’s natural defense against dis-ease). When you get exposed to anew, harmful germ, your bodydevelops cells called antibodiesthat are custom-made to fight thatgerm. It’s a good system, and itworks a lot better than you proba-bly realize (since it’s often keptyou from getting sick in the firstplace!). But making those antibod-ies takes time, and if an infection

is powerful enough, the germs cantake advantage of that “lag time”to do a lot of damage or to multi-ply and spread so much thatthey’re difficult or impossible todefeat.

Vaccines give your body a headstart. Usually, a vaccine contains akilled or weakened form of thegerm that causes a disease, or justa few important pieces of it.

A child gets a polio vaccine, which will prevent his getting the disease, at an inoculation clinic.

Whatever the case, it’s enough tomake your body produce antibod-ies to the germ, without gettingyou sick. So in the future, ifyou’re ever infected with thegerm, those antibodies are readyto attack it right away, before itgets out of control. Some vaccines,such as the one for tetanus,require booster shots every sooften to keep the antibodiesprimed and ready. Others last awhole lifetime from just one dose.

Sometimes, the use of vaccinescan even protect people whoaren’t vaccinated. If a lot of peo-ple in an area are vaccinatedagainst a particular germ, thegerm won’t be able to live andgrow inside very many people. As a result, the disease-causinggerms start to die off.

The earliest form of vaccinationwas variolation, which waspracticed in China as early as the10th century. It was used as away to prevent the deadly diseasesmallpox. In variolation, healthypeople were exposed to powderedsmallpox scabs, often by stickingthem up their noses! Variolationoften caused mild sickness andsometimes resulted in death, butoverall it was thought to lowerthe rates of full-blown smallpox.

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COMMON VACCINATIONS

The Centers for Disease Control recommends a number of differentvaccines for children. Different vaccines work best at different ages.Some vaccines can be given to very young infants. Others work better when given to children who are a year old or more.

Some vaccines require only one shot. Others are given in severalshots, months or years apart.

Although it is important to vaccinate your children as early as possible, it is never too late. So even if your child has fallen behindschedule, he or she will benefit from being vaccinated as soon aspossible.

Here are the vaccinations every child should get and when theyshould be given:

Vaccine Number Age for Other of doses first dose doses

Hepatitis B 3 Birth–2 mos. 1–4 mos., 6–18 mos.

Hib 4 2 mos. 4 mos., 6 mos., 12 mos.(meningitis)

Polio 4 2 mos. 4 mos., 6–18 mos., 4–6 yrs.

DTaP 5 2 mos. 4 mos., 6 mos., 15–18 (diphtheria, mos., 4–6 yrs.tetanus, Tetanus booster shotsand recommended everypertussis) 10 years.

PCV (Bacterial 4 2 mos. 4 mos., 6 mos., 12–15 Meningitis) mos.

MMR 2 12–15 mos. 4–6 yrs.(measles, mumps, rubella)

Varicella 1 12–18 mos. (chickenpox)

Hepatitis A* 2 2+ yrs At least six months later

*Recommended in certain areas; ask your doctor.

The first real vaccine is credited toan English country doctor namedEdward Jenner. He had noticedsimilarities between smallpox andcowpox, a disease found in cows.Humans could catch it, too, but thedisease was mild compared withsmallpox.

Some of the villagers that Jennertreated claimed that catching cow-

pox kept a person from gettingsmallpox. Jenner began to takedetailed notes on the subject andfound that the story seemed to be

true. Finally, he decided to test it.In 1796, he deliberately vaccinateda young boy named James Phippswith cowpox. Sure enough, the boydidn’t catch smallpox when he wasexposed to it.

This kind of vaccination becamepopular throughout Europe andthe United States in the 19th cen-tury. However, it wasn’t universal-ly accepted. Some people didn’tbelieve it really worked. Othersthought it was disgusting andunnatural to be infected with theblood of an animal. Still othersobjected to laws that made vacci-nation mandatory. And, of course,the vaccine still caused a sickness,so people had to accept definitely getting cowpox just toavoid the possibility of gettingsmallpox. Today, many effectivevaccines use viruses that areweakened in some way, making it much less likely that the vaccines will cause disease.

One of the most successful modern vaccines was the one for poliomyelitis (or polio). This vaccine was invented by Dr. Jonas Salk in 1953. It used an inactivated form of the poliovirus that couldn’t make you sick.*

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Dr. Jonas Salk developed the polio vaccine,which he gives to a Pittsburgh boy in 1954.

*In 1957, Dr. Albert Sabin began testinga live, but weakened, form of the virusas a vaccine to improve upon Salk’s vac-cine.

Before the vaccine, polio causedmany deaths and disabilities.(Most famously, it left U.S.President Franklin DelanoRoosevelt unable to walk withoutcrutches.) When the polio vaccinewas first introduced, people linedup for blocks and blocks to get it.

Over the years, polio and manyother serious diseases (includingmeasles, mumps, and rubella)have been kept well under con-trol with safe, effective vaccines.Today, a long list of vaccines isrecommended for infants andtoddlers as soon as they’re oldenough to handle them, so thatthey can be protected from thesediseases for life.

THE FIGHT AGAINST INTRINSIC DISEASES

What are intrinsic diseases?

Not all illnesses are caused byinfections. Many fall into a cate-gory called intrinsic diseases.(“Intrinsic” means “from within”or “relating to a natural part.”)Unlike infectious and transmissi-ble diseases, which are caused bygerms that enter the body fromthe outside, intrinsic diseases areproblems that arise within thebody. In other words, they arefailures of the body’s naturalfunctions.

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THE ETHICS OF JENNER’S STUDY

On the surface, Edward Jenner’s study may seem unethical. Hedeliberately inoculated a young boy with cowpox for the sake of ascientific experiment. He probably didn’t ask the boy or his parentsto sign any legal forms before he did it, either.

However, Jenner was more careful than some people realize. In theyears before his experiment, he had taken detailed notes on theeffects of cowpox on the villagers. He noted that nobody who hadcowpox got smallpox later on, even if he or she had cowpox morethan 25 years earlier. What’s more, the villagers that Jenner studiedroutinely variolated themselves with actual smallpox, and youngJames Phipps was next in line. So vaccinating him with cowpox wasno worse than exposing him to smallpox, and, in fact, it kept himfrom getting sick when he was exposed to the smallpox virus sixweeks later.

If Jenner had done his study today, he would have had to clearmany more legal and ethical hurdles before actually carrying it out.Still, it’s fair to say that Jenner did his best to ensure the safety ofhis first subject under the circumstances.

“Directfrom theCow!”,1877. A localinspectoris endeav-ouring toestablishwhetherthewoman’sson hasbeen vac-cinated.Therewere anumberof seriouscholera epidemics in the mid-nineteeth century and, followingEdwin Chadwick’s report into public health, local health officialswere appointed and a number of Public Health Acts were passedto reduce disease. The smallpox vaccine had been developed atthe beginning of the century by Edward Jenner and it may bethis that the inspector was referring to. From “Punch, or theLondon Charivari”, March 24, 1877.