Diseases that are more common among children than among adults are referred to as childhood diseases. That is not to say that adults cannot or will not contract these illnesses, but usually children contract these diseases and form the immunity against them that will protect them as adults. In fact, some of these diseases may be quite uncomplicated in childhood, but may be life-threatening when contracted in adulthood by someone who never had the disease as a child. Vaccines provide immunization against some of these diseases; others, however, can neither be prevented nor cured.
Although the first vaccination for any disease was administered in the late eighteenth century, the development of immunology proceeded slowly for the next hundred years. Dr. Edward Jenner (1749–1823), an English physician, noticed that milkmaids who developed cowpox from contact with cows were immune to smallpox. He correctly hypothesized that exposure to the cowpox somehow conferred protection. Jenner withdrew some of the material from the milkmaids’ skin pustules and injected it under the skin of a young boy; Jenner then proved the inoculation by injecting the boy with smallpox matter, which did not give the boy smallpox. Jenner’s method was soon accepted throughout Europe and America, and the death rate from smallpox fell sharply.
Some childhood diseases are brought on by a bacterium or virus (chickenpox or measles, for example); others are inherited (Tay-Sachs disease or sickle cell anemia); and still others are caused by heavy use of alcohol or drugs by the mother while she is pregnant.
Many childhood diseases are contagious—that is, can be passed on from one person to another by transmission of the bacterium or virus. Children are brought together in school buses and classrooms, and these close quarters are ideal for the transmission of the etiologic agents that cause diseases. When one child contracts measles, usually several in the same bus or class will also get the disease before steps can be taken to slow the rate of transmission, because such infections are often most contagious before any outward symptoms appear. Similarly, a child with mumps can infect a number of others before actually showing signs of being ill. This type of transmission is particularly true of the common cold. The virus that causes the cold is especially numerous in the early stages of the cold, before the patient actually starts to sneeze and develop a fever.
Much research is directed toward developing vaccines and remedies for diseases that are presently incurable (e.g., the common cold or AIDS), but virus-borne diseases are much more difficult to cure or prevent than bacterial diseases. A virus cannot be seen under the normal light microscope used in laboratories. A special electron microscope must be used to see a virus. Viruses can also change or mutate to fend off any natural immunity that may develop against them. In addition, some diseases, such as the common cold, are caused by more than one virus. A cold can be brought on by any one of some 200 viruses. A vaccine, if developed, would be effective against only one virus; many scientists feel such a vaccine would hardly be worth the trouble to develop. Even diseases that are caused by a single virus (such as AIDS) can defy the development of an effective vaccine.
The etiologic agents of contagious diseases can be passed from one person to another in any number of ways. They are present in droplets of saliva and mucus sprayed by sneezing and coughing. They can be conveyed by passing an object from the infected person to someone else. With the close proximity of children in classrooms, the agent can be passed quickly through the class.
Chickenpox is one of the most easily transmitted childhood diseases; it is second only to measles. It is caused by the varicella-zoster virus, which may reactivate to cause shingles in individuals who have already had chickenpox. After exposure to the virus, a 7-21 day period of incubation occurs before any symptoms appear. Chickenpox begins with a low fever and general feeling of tiredness. Soon a rash develops on the abdomen and chest, which may or may not spread to the extremities, but usually affects the scalp. The rash appears in successive stages; as a result, some of the bumps are mature while others are just appearing. The rash progresses from the initial red bumps through a vesicle stage, in which they are filled with liquid, to a mature, crusty stage. Itching is intense, but scratching can cause localized infection of the broken vesicles and may require antibiotics. Within a week after the appearance of the rash, the patient is no longer infectious.
There is no treatment for chickenpox, but the Food and Drug Administration approved a varicellazoster vaccine in March 1995. The live-virus vaccine, developed from a strain of the virus isolated in Japan in 1981, is recommended for children between the ages of 12-18 months. A person also develops immunity to the virus if he has experienced an outbreak of chick-enpox. The outbreak is usually harmless to children and passes within a week without any noticeable permanent effect. In adults the disease is much more serious; it can cause damage to the eyes and, in males, the testes. An adult with chickenpox also requires a longer period of recuperation than does a child. Pregnant women who contract chickenpox may pass the infection on to their unborn child, with serious consequences. Varicella-zoster immunoglobulin may be given to such pregnant women, in an effort to decrease the complications to the fetus. Children who have weakened immune systems (due to chemo–therapy treatments for cancer, for example) may have severe, life-threatening complications from chicken-pox. Antiviral medications such as acyclovir may be given in an attempt to decrease the severity and shorten the duration of the illness.
Even when the infection has disappeared, however, the virus remains in the person’s body and can cause shingles later in life. The chickenpox virus lies dormant in some nerve cells and can become active later in life; the nerve root becomes inflamed, and the area of the body served by that nerve is affected. Another eruption occurs, but in this case it is very painful. A rash may appear on the abdomen or any area of the arms or legs. The outbreak lasts for five to six days, unless the patient has an underlying cancer, in which case the rash may persist for two weeks or longer.
It is not possible to predict who will have shingles after they have had chickenpox. There is no treatment for shingles, but usually an individual will have it only once and then be immune to any further outbreaks. If the virus infects certain facial nerves, care must be taken to prevent damage to the eyes. Unlike chicken-pox, shingles is not contagious. The virus is confined to the nerve fiber and is not released into the air.
Measles generally refers to nine-day measles, also called rubeola, a highly contagious disease spread by a virus. A person who has the measles virus can pass it to others before he shows signs of the disease. Once exposed to the virus, it will be 7-18 days before the typical measles rash develops. The patient is infectious, however, for the two to four days immediately before the rash appears; thus he spreads the disease unknowingly. Present in mucus and saliva droplets from the nose and mouth, the virus is spread by coughing or sneezing.
The initial symptoms of measles include headaches, a low fever, tiredness, and itchy eyes. Spots appearing on the roof of the mouth look like white grains of sand surrounded by an inflamed area. These are called Koplik spots. A sore throat may also develop. The rash appears three to five days later: a bright red outbreak usually begins on the side of the head in front of the ears and spreads over the body within the next day or two. The temperature may climb to 104°F (40°C). Inflammation of the eyes may cause painful sensitivity to light.
The disease is short lived; the rash fades within three to five days and the body temperature returns to normal. The disease, while active, renders the patient much more susceptible to bacterial infections and may worsen diseases such as tuberculosis, if present. Pneumonia and ear infections are common complications of measles, especially in infants and very young children. Also, the virus can penetrate the central nervous system and cause encephalitis (inflammation of the brain tissue), which can lead to convulsions, coma, and even death. A person with measles should have bed rest during the active stage of the disease and be protected from exposure to any bacterial infections.
Fortunately, a vaccine has been developed against measles. The vaccine is a suspension of a live attenuated (weakened) virus that is given to children at the age of approximately 15 months. The vaccine causes the formation of antibodies against the measles virus that will protect the child from future infections.
Another form of measles, known as three-day measles, German measles, or rubella, is also caused by a virus. Contagion is high because the infected person can transmit the virus to others for a week before showing any symptoms, and remains infectious for up to a week after the measles rash disappears.
Rubella is less infectious than the nine-day measles, and some infections may be so mild that the patient’s case of rubella goes undetected. After exposure to the virus, an incubation period of 14-21 days passes before any symptoms appear. Usually the symptoms afflict only young children; teenagers and adults will not develop the typical rash, which is similar to that of nine-day measles but is less extensive. It appears on the face and neck and may spread to other areas. The rash lasts about three days before fading. No other symptoms, such as a sore throat, accompany the rash.
The most serious complication of three-day measles is its effect on a woman in the early stages of pregnancy. The virus can cause loss of the fetus or stillbirth, or it may result in congenital (birth) defects. These can include heart defects, eye defects (including glaucoma and cataracts), deafness, bleeding problems, mental retardation, and an increased risk of diabetes mellitus, thyroid problems, and future encephalitis (brain inflammation). A woman in the first three months of pregnancy should be protected from exposure to individuals who have measles. This form of measles can also be prevented by vaccination.
Mumps, also called epidemic parotitis, is a viral infection of the salivary glands, especially the parotid glands. The mumps virus is spread in droplets of saliva sprayed during sneezing or coughing and can be passed along on any object that has the infected saliva on it. The virus is present in the saliva of the infected person for up to six days before symptoms appear. Late winter and early spring are the peak periods of mumps epidemics, and children aged 5-15 years are most commonly infected. The disease is not as infectious as chickenpox or measles, and it is rare in children under two years of age.
The first symptom of mumps is pain during chewing or swallowing, which is worsened by acidic foods. The parotid gland, located in the area at the angle of the jaw, becomes sensitive to pressure. Body temperature increases to 103-104°F (40°C). The infected parotid gland becomes inflamed and swollen; the swelling may extend beyond the gland to the ear and the lower area of the jaw. The swelling reaches its maximum within two days and then recedes.
The mumps virus can also penetrate the central nervous system and cause abnormally high numbers of cells to accumulate in the spinal fluid. Usually this form of encephalitis has no residual effects, although rarely some facial paralysis or deafness due to auditory nerve damage may result. Mumps afflicting an adult male can cause atrophy of the testes and, in some cases, subsequent sterility. Patients should remain in bed until the fever accompanying the disease has subsided.
There is no treatment for mumps. Usually it is benign and will leave no residual effects other than a natural immunity against catching it again. During the illness, patients may take aspirin to ease the pain in the jaw and lower the fever. Eating soft food also helps to ease jaw pain. Anyone who has been in contact with a mumps patient should be watched closely for up to four weeks to see whether he or she will also develop the disease. A live-virus mumps vaccine is available for administration to children who are 15 months of age.
As recently as the early decades of the twentieth century, childhood was fraught with diseases that often entailed suffering and premature death. Many of those diseases were highly contagious; a child who contracted one of them was immediately isolated at home and a quarantine sign was posted conspicuously on the door to warn others. These once-perilous diseases included diphtheria and whooping cough (pertussis), which have been effectively controlled by vaccines; scarlet fever, another such disease, is now easily treated with antibiotics.
Diphtheria is caused by a toxin-producing bacterium, Corynebacterium diphtheriae, which infects the nervous tissue, kidneys, and other organs. The disease is spread by contact with the secretions of an infected person or objects that have the bacterium on them. Diphtheria develops rapidly after a short incubation period of one to four days. The bacterium usually lodges in the tonsils, where it multiplies and begins to produce a toxin. The toxic exudate, or secretion, is lethal to the cells around the infected area and can be carried to distant organs by the blood. Areas of infection and damage can be found in the kidneys, heart muscle, and respiratory tissues, as well as in the brain. A membrane that is characteristic of the infection forms over the area affected by the toxin.
If left untreated, diphtheria can cause serious heart damage that can result in death, nerve damage resulting in a palsy, or kidney damage that is usually reversible. Penicillin and a diphtheria antitoxin are now used to neutralize the bacterial secretions. One of the earliest vaccines now given to children is a combined vaccine for diphtheria, pertussis, and tetanus; as a result, diphtheria is now rare.
Pertussis, or whooping cough, so named because of the characteristic high-pitched crowing sound of the breath between coughs, is another highly infectious bacterial disease. The etiologic agent is the bacterium Bordetella pertussis.
Pertussis is known throughout the world. It is transmitted in the saliva of coughing patients who have the bacterium, usually in the early stages of the disease. Patients are no longer infectious after eight weeks. The bacterium invades the nose, pharynx (back of the throat), trachea (windpipe), and bronchi. Symptoms appear after an incubation period of about one to two weeks. The earliest stage of the disease consists of sneezing, fatigue, loss of appetite, and a bothersome nighttime cough. This stage lasts for about two weeks, after which the coughs become rapid (paroxysmal) and are followed by the characteristic whoop, a few normal breaths, and another paroxysm of coughing. The coughing spells expel copious amounts of thick mucus, which may cause gagging and vomiting. This stage of the disease can last up to four weeks, after which the patient begins a recovery; the coughing lessens and the mucus decreases.
Pertussis may be fatal in very young children; it is rarely serious in older children and adults. Fatalities in young children are usually caused by a subsequent bout of pneumonia. Infected individuals should be isolated, but do not necessarily need bed rest. Very young children should be hospitalized so that mucus may be suctioned from the throat area. A pertussis vaccine is available and is part of the early inoculation program in children. It is given with the vaccines for diphtheria and tetanus. Newer acellular pertussis vaccines cause fewer side effects than the old whole cell vaccines.
Poliomyelitis, also called polio or infantile paralysis, is caused by a virus and once appeared in epidemic proportions. It occurs mostly in young children and appears primarily in the summer or fall. Poliovirus, the causative agent, is found in three forms—types I, II, and III. Type I is the most likely to cause paralysis.
Most people who host the poliovirus do not develop any symptoms but can still spread the virus. Because it is present in the throat of infected individuals, the virus is spread by saliva. Polio is known worldwide, and cases of it occur year round in tropical areas. Fortunately, only one of every 100 people who have the virus actually exhibits the symptoms of polio.
At one time polio was so widespread that many young children developed an immunity to polio very early in life, because they would acquire the virus without fail. With the onset of hygienic sanitation, however, the disease began to appear as epidemics in developed countries. Since children no longer develop a natural immunity, as they did prior to the installation of modern sewage facilities, an outbreak of polio can quickly sweep through the younger population.
The onset of polio is divided into two phases: a minor illness and a major illness. The minor illness, experienced by about 90% of those who contract the virus, consists of vague symptoms such as headaches, nausea, fatigue, and a mild fever. These symptoms pass within 72 hours, and for most victims this is the extent of the disease. Those who acquire the major illness, however, combat a much more drastic form. It begins with severe headaches during the 7-35 days following exposure to the virus. A fever develops, and stiffness and pain in certain muscles appear. The affected muscles become weak and the nerve reflexes to those muscles are lost. This is the beginning of the paralysis, which results because the virus infects certain areas of the nervous system, preventing control of muscle groups.
A vaccine is available to prevent polio. The first polio vaccine was given by injection, but a later version was given orally. The latest guidelines for polio immunization state that IPV (inactivated poliovirus vaccine, supplied via injection) should be given at two and four months of age; subsequent immunizations at 6-18 months and 4-6 years may be given either as injection or orally. These newer guidelines were designed to decrease the rare complication of vaccine-induced polio infections which increased when all doses were given orally (which is a live virus vaccine).
Noncontagious childhood diseases are acquired by heredity—that is, passed from parents to offspring. In fact, neither parent may have any physical signs of the disease, but if they are carriers—people who have the recessive gene for the disease—they can pass it on to their children.
Some of these conditions are serious or even fatal, with no cure for the person who has the disease. Some effective preventive measures can be taken to keep the disease in an inactive state, but even these measures are sometimes not effective.
Sickle cell anemia
Sickle cell anemia is named for the shape assumed by some of the red blood cells in persons who have this disease. It primarily affects people of African descent, but it can also be present in people of Mediterranean descent, such as Arabs and Greeks.
Some people carry the gene for sickle cell anemia without having any active symptoms. For those in whom the disease is active, however, a “sickle cell crisis” can be a painful and debilitating experience.
When the red blood cell undergoes changes that alter its shape from a disk to a sickle, the cells can no longer pass easily through the tiniest blood vessels, the capillaries. The sickle cells stick in these vessels and prevent the passage of normal cells; as a result, the organ or muscle dependent on blood flow through the affected capillaries is no longer getting oxygen. This causes a very painful crisis that may require hospitalization.
No cure exists for sickle cell anemia, so the person who has the active disease must avoid infections and maintain a healthy lifestyle. Any activity that is strenuous enough to cause shortness of breath can also bring on a crisis.
Tay-Sachs disease is an inherited, invariably fatal condition in which a missing enzyme allows certain toxic substances to accumulate in the brain. Under ordinary circumstances the enzyme, hexosaminidase A, breaks down these toxins, but without its presence the toxins accumulate.
The condition causes the development of red spots in the eye, retarded development, blindness, and paralysis. The child usually dies by the age of three or four. Tay-Sachs disease primarily affects Jews from eastern Europe.
Parents who carry the gene for Tay-Sachs can be counseled about having children. Statistically for parents who are both carriers of the gene, one in four children will have the active disease, two of the four will be unaffected carriers of the gene, and one of four will have neither the gene nor the disease.
Some conditions are passed from mother to child not as a result of an infection or a genetic malfunction, but because the mother has failed to provide an optimal prebirth condition for the developing baby. The placenta, which lines the womb and serves to nourish the developing infant, can be penetrated by substances such as alcohol, nicotine, cocaine, and heroin. Also, a mother who has AIDS can pass the virus to the child during gestation or delivery of the child.
The mother who smokes, drinks alcohol, or uses drugs while pregnant can cause developmental problems for the child. The fetus is especially susceptible to these influences during the first three months (first trimester) of pregnancy. The organs are formed and the anatomy and physiology of the infant are established during the first trimester.
Fetal alcohol syndrome (FAS) is a well-recognized affliction brought about by the mother’s heavy consumption of alcohol during pregnancy. Alcohol consumed very early in the pregnancy can cause brain damage by interfering with the fetus’s brain development. Other features of a child with FAS are wide-set eyes, flattened bridge of the nose, and slowed growth and development.
A child born of a mother addicted to drugs will also be addicted. Often the baby will exhibit signs of withdrawal, such as shaking, vomiting, and crying with pain. These children usually have a low birth weight and are slow to develop. In time, once the drug is out of his system, the child may assume a normal life pattern.
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