What are bacterial infections?

Causes and Symptoms

Bacteria are very small, one-celled organisms (the cell being the smallest unit of a living organism) with an average size of thousandths of a millimeter. Based on their relatively simple structure, they are classified as prokaryotic cells. Prokaryotic cells have a rigid outer cell wall, very simply organized hereditary material (deoxyribonucleic acid, or DNA) floating free within the cell, and only a few other structures necessary for their survival, growth, and reproduction. Eukaryotic cells, such as those found in humans, plants, and other animals, have highly organized DNA and many more internal structures. Despite the fact that bacteria are relatively “simple,” they are still very complex living organisms.

The many types of bacteria can be divided into three categories based on their shape: coccus (round), bacillus (rod-shaped), or spirillum (spiral). Another major distinction between types of bacteria is based on the sugar and lipid (fat) composition of their cell walls. This difference can be identified through Gram staining, the result of the stain determining whether the organism is gram-positive or gram-negative. Various types of bacteria may have additional structures that are useful in their identification. Capsules and slime layers are water-rich sugary materials secreted by the bacteria that cling to their surfaces and form halolike structures. Flagella are long, thin, whiplike structures found in one location on the bacterium or occasionally covering its entire surface. These structures are used to enhance the motility, or movement, of the bacteria.

Some bacteria are normal, harmless inhabitants of human bodies, such as those on the surface of the skin. Others, such as those that live in the human intestinal tract, aid in digestion and are essential for good health. The warm, moist, nutrient-rich human body also provides an excellent breeding ground for numerous harmful bacterial invaders. For bacteria to cause infectious disease, several stages must occur. The bacteria must enter the person, they must survive and multiply on or in the person, they must resist the natural defenses of the human body, and they must damage the infected person. Most bacterial diseases are infectious because of the ease with which they can be transmitted from individual to individual by physical contact with the person, a contaminated object, or bacteria expelled into the air, such as by coughing or sneezing. A few bacterial diseases, such as food poisoning, are not classified as infectious.

Bacterial infections cause disease by a variety of mechanisms. Many of them produce chemical compounds that are toxic to human beings. For example, Salmonella
and Staphylococcus aureus are two types of bacteria that are capable of causing food poisoning. Clostridium botulinum produces the deadly
botulism toxin. In each case, ingestion of the toxin in contaminated food can lead to serious illness. Clostridium tetanii can enter the body through puncture wounds and will multiply rapidly deep in tissue where there is little exposure to the air. The toxin that it produces acts on the central nervous system and causes severe muscle spasms, which can lead to death from respiratory failure. Water that has been contaminated with raw sewage is a potent source of disease-causing bacteria. Vibrio
cholera

produces a potent toxin that causes severe diarrhea leading to death if it is not vigorously treated. Certain varieties of Escherichia coli and Shigella found in contaminated water can also cause severe intestinal disorders. Toxic shock syndrome is associated with the production of toxins by Staphylococcus aureus.

Another common cause of disease from bacterial infections is the result of the physical destruction of tissue by the invading organisms.
Leprosy (also called Hansen’s disease), caused by Mycobacterium leprae, if left untreated, can lead to severe deterioration and disfiguration of large areas of a person’s body. If a wound interrupts the blood supply to an area of the body such as a hand or foot, the tissues begin to decay, thereby providing nutrients for many bacteria, especially Clostridium perfringens. These bacteria can greatly accelerate the destruction of the tissue, which causes the condition known as gas
gangrene.

In many cases, disease results when the infecting bacteria are recognized by the body’s natural defense system (the
immune system) as “nonself,” that is, as invaders. Certain cells within the body are designed to attack intruders and eliminate them. During this process, disease symptoms that are consequences of the immune system’s response may be evident: inflammation (redness and swelling), the production of pus, and fever, among other symptoms. In some cases, certain components of the bacteria, such as capsules and slime layers, may protect them from being eliminated by the immune system. The bacteria may also multiply exceedingly rapidly, producing increasing amounts of toxins that overwhelm the capacity of the immune system to eliminate them. In these cases, continued and increasingly elevated disease symptoms such as fever can cause severe, even fatal, damage unless an alternate method for eliminating the infection is found. Failure to eliminate the bacterial invaders can also lead to a long-term, chronic infection that damages body tissues.

Many
respiratory diseases are associated with the body’s immune response to bacterial invasion. Streptococcus pyogenes is the causative agent of
strep throat, whose features include severe redness, inflammation, pain, and the production of pus in throat tissue. In a small percentage of cases, strep throat can also lead to an infection of and potential permanent damage to the heart
valves in a disease called rheumatic fever. In tuberculosis, Mycobacterium tuberculosis
enters the lungs through inhalation. The body’s defense system walls off the intruders and forms a nodule called a tubercle deep in the lung tissue. Nevertheless, the bacteria continue to multiply in the nodule and can travel to new sites in the lung. Tubercle formation occurs at these new sites. Eventually, this
repeated cycle of infection and nodule formation becomes a chronic disease and leads to the destruction of lung tissue. Bacterial
pneumonia can be caused by several different organisms, including Klebsiella pneumoniae and Mycobacterium pneumoniae. A pneumonia-like disease, Legionnaires’ disease, was first identified in 1976 after twenty-nine delegates to an American Legion convention died from a mysterious respiratory disorder. The lengthy process of identifying a causative agent led to the discovery of a type of bacteria not previously known, Legionella pneumophila.

The human urinary and genital tracts are also potential havens for invading bacteria. Cystitis (bladder infections) are caused by many different types of bacteria. Kidney infections can be acquired as corollaries of urinary tract infections. Sexually transmitted diseases (STDs)
are contracted through sexual contact with an infected partner, and two common STDs have a bacterial origin.
Gonorrhea is caused by Neisseria gonorrhoeae and leads to a severe inflammatory response and rapid spread of the organisms throughout the body. If not treated, it can lead to sterility as well as to diseases of the joints, heart, nerve coverings, eyes, and throat. Syphilis, caused by Treponema pallidum, can also have serious consequences if left untreated, including dementia and death. In addition, it can be passed to a fetus developing inside an infected mother in a condition known as congenital syphilis.

Treatment and Therapy

The medical management of the many bacterial infections and the diseases they cause begins with diagnosis. Diagnosis relies on a variety of biochemical tests that are analyzed in conjunction with the signs and symptoms exhibited by the infected individual. Treatment is then designed so that it not only eliminates the disease symptoms but also eradicates all invading bacterial organisms, thereby minimizing the chance of a recurrence of the disease. Prevention involves steps that the individual takes to avoid potential contact with infectious diseases, as well as the use of medical procedures that protect against specific bacterial diseases.

To treat a bacterial disease properly, the invading organism must be identified correctly. In some cases, symptomology can be specific enough to identify the offending bacterium, but since there are literally thousands of different types of disease-causing organisms, a systematic approach using a variety of tests is undertaken to make a definitive diagnosis. First, a specimen from the infected person is collected. This may be a blood or urine sample; a swab of the infected area, such as the throat or another skin surface; or a secretion, such as sputum, mucus, or pus. Since human bodies are normally inhabited by a variety of harmless bacteria, the individual types of bacteria are isolated in pure cultures, in which each bacterium present is of the same type. The pure cultures are then tested to determine the identity of the organisms. Staining procedures, such as Gram staining, and microscopic examination of the stained bacteria to determine the Gram reaction and the shape of the bacteria can narrow down the identity of the organisms considerably.

Based on these results, a standard series of tests is performed, continually narrowing down the possible identities until only one remains. One test measures the organisms’ growth requirements. Many identifications are aided by analyzing the types of sugars and proteins that the organisms can use as food sources. The by-products of their metabolism (chemical reactions occurring inside the bacteria), such as acids and gas, are identified. Oxygen requirements, motility, and the presence of a capsule are three other common characteristics that are examined. For cases in which the identification of a particular variety of one type of bacteria is necessary, more complex tests may be undertaken, such as an analysis of the particular sugars and proteins on the surface of the organism or tests for the production of specific toxins. Once the bacterium’s identity is confirmed, treatment may begin.

The most common type of treatment for bacterial infection is antibiotic therapy.
Antibiotics are chemical compounds that kill bacteria. Originally discovered as antibacterial compounds produced by bacteria, molds, and fungi (such as penicillin from bread mold), many more are synthetically produced. Antibiotics work in a variety of fashions. Some, such as penicillin and the cephalosporins, interfere with the synthesis of cell walls by bacteria, thus preventing the organisms from multiplying. Other commonly used antibiotics prevent the bacteria from synthesizing the proteins that they need to survive and multiply. These include the tetracyclines (a class of antibiotics that act against a large range of bacteria), erythromycin, and streptomycin. A host of other antibiotics target a variety of bacterial functions, including specific chemical reactions and the propagation of genetic material, and the structural components of the bacteria. Each class of antibiotics works best on certain types of bacteria. For example, penicillin is most efficient in killing cocci (such as Streptococcus and Staphylococcus) and
Gram-positive bacilli.

Frequently, the symptoms of a bacterial disease may disappear rapidly after the beginning of antibiotic therapy. This reaction is attributable to the inhibition of bacterial multiplication and the destruction of most of the microorganisms. A small number of the bacteria may not be killed during this initial exposure to antibiotics, however, and if antibiotic therapy is ended before all are killed, a recurrence of the disease is likely. A full prescription of antibiotics should be taken to avoid this situation. For example, effective treatment and eradication of all bacteria in tuberculosis may take six months to a year or more of antibiotic treatment, despite the fact that the symptoms are alleviated in a few weeks.

Upon repeated exposure to a type of antibiotic, some bacteria develop the capacity to degrade or inactivate the antibiotic, thus rendering that drug ineffective against the resistant microorganism. In these cases, other antibiotics and newly developed ones are tested for their effectiveness against the bacteria. Such situations have arisen in the bacteria that cause gonorrhea and tuberculosis.

While antibiotics exist to combat infections of most types of bacteria, in some cases the human immune system is capable of clearing the infection without additional intervention. In these instances, the symptoms of the infection are treated until the body heals itself. This is the common treatment path in mild cases of food poisoning, such as those caused by some Salmonella and Staphylococcus varieties. Diarrhea and vomiting are treated by replacing water and salts, by drinking large volumes of fluids, and perhaps by using over-the-counter remedies to ease some of the symptoms.

Many bacterial diseases can be easily prevented through good hygiene. Foods, such as eggs and meats, that are not thoroughly cooked may become quickly contaminated by the rapid growth of food-poisoning organisms present on their surfaces. Proper cooking kills these organisms. Similarly, foods that are not properly stored but left out in warm places can also provide a potent breeding ground for toxin-producing bacteria. Picnic food not properly refrigerated is a common source of food poisoning. Similarly, questionable water sources should never be used for drinking or cooking water without proper treatment. Filtering with an ultrafine filter specifically designed to remove bacteria is one safeguard, as is boiling for the required time period based on altitude. Food that may have been washed with contaminated water sources should always be cooked or peeled before consumption.

Many diseases can be prevented with vaccinations. A bacterial vaccine is a mixture of a particular bacterium, its parts, or its inactivated toxins. When this solution is injected into an individual, it provides immunity (resistance to infection) to the particular organism contained in the vaccine. Some vaccines provide lifetime immunity when enhanced with an occasional booster shot, while some are relatively short-acting. Many types of vaccines that are directed against specific diseases are part of standard preventive care given to children. For example, the DTaP vaccine (or Tdap for adults) confers immunity to diphtheria, pertussis (whooping cough), and tetanus. Some vaccines are useful for individuals who are living, working, or traveling in areas where certain diseases are endemic, or for those who regularly come into contact with infected individuals. Examples of these sorts of vaccines include those for plague (Yersinia pestis), typhoid fever (Salmonella typhi), cholera, and tuberculosis.

Perspective and Prospects

Bacteria were first described as “animalcules” by the Dutch scientist Antoni van Leeuwenhoek
in 1673 after he observed them in water-based mixtures with a crudely designed microscope. In 1860,
Louis Pasteur recognized that bacteria could cause the spoiling of wine and beer because of the by-products of their metabolism. Pasteur’s solution to this problem was heating the beverages enough to kill the bacteria, but not change the taste of the drink—a process known as pasteurization, which is used today on milk and alcoholic beverages. In addition, Pasteur settled a long-standing debate on the origin of living things that seemed to arise spontaneously in fluids exposed to the air. He demonstrated that these life-forms were seeded by contaminating bacteria and other microorganisms found in the air, in fluids, and on solid surfaces. Pasteur’s work led to standard practices in laboratories and food processing plants to prevent unwanted bacterial contamination; these practices are referred to as aseptic techniques.

Prior to the late nineteenth century, deaths from wounds and simple surgeries were quite common, but the reason for these high mortality rates was unknown. In the 1860s, Joseph Lister, an English surgeon, began soaking surgical dressings in solutions that killed bacteria, and the rate of survival in surgical and wound patients was greatly improved. In 1876, Robert Koch, a German physician, discovered rod-shaped bacteria in the blood of cattle that died from anthrax, a disease that was devastating the sheep and cattle population of Europe. When he injected healthy animals with these bacteria, they contracted anthrax, and samples of their blood showed large numbers of the same bacteria. By these and other experiments, Koch, Lister, and others proved the “germ theory of disease”—that microorganisms cause disease—and appropriate measures were instituted to protect against the transmission of bacteria to humans through medical procedures and food.

A milestone in the prevention of infectious diseases was the development of vaccinations. The first vaccine was developed in 1798, long before the germ theory of disease was proven. The British physician Edward Jenner first used vaccination as a preventive step against the contraction of deadly smallpox, a viral disease. How vaccinations work and their use as a protection against bacterial diseases were discovered around 1880 by Pasteur.

The first antibiotic, penicillin, was discovered by Alexander Fleming in 1928. Since then, scores of others, produced both naturally and synthetically, have been analyzed and used in the treatment of bacterial diseases. All these discoveries have made bacterial disease a much less deadly category of illness than it was in the late nineteenth century. Yet bacterial diseases are by no means conquered. Overuse of antibiotics in medical practice and in cattle feed results in the appearance of new varieties of bacteria that are resistant to standard antibiotic therapy. Research will continue to develop new means of controlling and destroying such infective organisms. Bacteria also play an important role in synthesizing new antibiotics and other pharmaceuticals in the laboratory through recombinant DNA technology. These organisms will continue to provide challenges and opportunities for human health in the years to come.

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Wilson, Michael, Brian Henderson, and Rod McNab. Bacterial Disease Mechanisms: An Introduction to Cellular Microbiology. New York: Cambridge University Press, 2002.

Why do you think the theme is implied rather than stated in "Thank You, Ma'am" by Langston Hughes?

In Langston Hughes’ short story “Thank You, M’am” there are a number of implied themes. Why would the author imply the themes instead of stating them explicitly? By implying theme, the author allows the actions, thoughts, and emotions of the characters to teach a moral lesson. In addition, the setting of the story often contributes to theme, as it does in this story.

In “Thank You, M’am” the themes of kindness and trustworthiness are demonstrated by the actions of both Mrs. Luella Bates Washington Jones and Roger. Roger attempts to steal Mrs. Jones purse but she thwarts his actions. Instead of taking punitive action against him, she takes him to her home, where they come to an understanding of each other’s situations. She sees him as a product of his environment, and he learns that she is a hard-working, reliable woman who sees potential in him.

The woman said, “Um-hum! You thought I was going to say but, didn’t you? You thought I was going to say, but I didn’t snatch people’s pocketbooks. Well, I wasn’t going to say that.” Pause. Silence. “I have done things, too, which I would not tell you, son—neither tell God, if he didn’t already know. So you set down while I fix us something to eat. You might run that comb through your hair so you will look presentable.”

The setting contributes to the theme of rising above poverty. The action occurs late in the evening on the streets of Harlem, and in a single room of a boarding house. The setting provides background and breathes life into the character’s actions. Mrs. Jones’ works late catering to the clientele of a hotel beauty shop, while Roger allows his poverty to reduce him to petty thievery.

Therefore, in his story, Langston Hughes uses the actions of his characters and the setting of the story to develop theme.  He allows the reader to become emotionally involved with the characters, and teaches them about the consequences of social inequity.

Why are onion cells rectangular?

Plant cell structures are very similar across the range of plants that exist on Earth. All plant cells contain specific components, one of which is a cell wall. Cell walls, which do not exist in animal cells, are rigid in structure. Cell walls provide shape to form tissues and play a large role in determining what individual parts of a plant look like.

Because all plant cells have cell walls, plant cells have fixed rectangular shapes. If you look at an onion peel (or any piece of an onion) under a microscope, you will see clear evidence of a rectangular cell supported by the rigid structure of the cell wall. In contrast, animal cells, which do not have cell walls, will appear to be round.

Analyze in detail the collapse of the Han Dynasty (50 BCE-220 CE).

The Han Dynasty (50 BCE-220 CE) collapsed in part because of the corruption of the emperors. At the end of the first century (CE), one emperor after another died without an heir, and, often, a relative or even an infant was chosen with a guardian. The lack of a clear heir for many emperors meant that the court was riddled with intrigue and there was a great deal of political instability. In addition, China at the time was subject to many natural disasters, including plagues and floods. The public saw these problems as a sign that the dynasty had lost the mandate of heaven, and there were various internal revolts against the emperor. The eunuchs in court formed one powerful bloc (called the Ten Attendants) that opposed the government, and Confucians were also opposed to the corruption of the court.

In 184 CE, there was a peasant uprising called the Yellow Turban Rebellion (sometimes called the Yellow Scarves Rebellion), named after the clothing the rebellious forces wore on their heads. The rebellion was in part a reaction against widespread agrarian problems. A famine in the northern part of China forced many peasants to go south, where they were largely exploited by landowners. The Yellow Turban Rebellion was led by a man named Zhang Jue, who was an adherent of a Taoist sect that taught that land should be equally distributed among people. It took 21 years to suppress this rebellion. While the revolt was being put down, local governments gained power, furthering weakening the Han. In addition, tax collectors had a very difficult time collecting sufficient funds to support the empire, in part because of the ongoing agrarian problems.  

In addition, China was prey to foreign invasions, including during the Sino-Xiongnu Wars of 133 BCE to 89 CE. The Chinese fought the Xiongnu, who were Eurasian nomads, in the western areas of China. Though the Han won, their victory came at the price of weakening their empire.

At the end of the Han Dynasty, China was ruled by the Emperor Xian. There was much internal opposition to him, and several warlords opposed the emperor. One warlord, Cao Cao, tried to unite the empire under Xian. However, other warlords attacked forces loyal to the emperor at the Battle of Red Cliffs in 208-209 CE. The Han were defeated at this battle, and Cao Pi, the son of Cao Cao, ultimately forced Emperor Xian to abdicate, leading to the end of the Han Dynasty in 220. A new emperor called Sun Quan then ruled, beginning the era of the Three Kingdoms. 

What was Julius Caesar's relationship with the Senate from when he was born to his death/assassination and what are some good web resources and...

Julius Caesar is one of the most famous political and military figures in world history. Without him and his populist leanings and activities the Roman Senate might never have opposed him as vehemently, and thus would have not changed to the extent it did.

Caesar grew to manhood during the time of The Roman Republic, not The Roman Empire. His life and contributions would cause his heir, Augustus, to be the first true "emperor".

His relationship with the Senate was always one of conflict and uneasy tolerance. The disregard that Caesar showed for the wishes of the Senate in his military days are well summed up by his crossing the Rubicon in 49 BC in defiance of their orders. Hence the term "crossing the Rubicon" has come to mean taking an action that puts one across the point of no return.

The Life and Times of Julius Caesar, by Whiting

Caesar: A History of the Art of War Among The Romans, by Dodge

What are sexually transmitted diseases (STDs)?

Causes and Symptoms

Sexually transmitted diseases, or STDs (formerly called venereal diseases), have plagued humankind for centuries. The most prevalent, serious STDs are syphilis, gonorrhea, nongonococcal urethritis, trichomoniasis, genital herpes, genital warts, viral hepatitis, and AIDS. Others, troublesome but not as serious, include lice, scabies, and vaginal yeast infections. They are passed on from one person to another mostly by sexual contact, although some of these diseases may be acquired indirectly through contaminated objects or blood. In addition, nearly all these diseases can be passed on from an infected mother to her fetus, which may cause birth defects, severe and damaging infections, or even death. A person can acquire several STDs at the same time, and since recovery from an STD does not confer immunity, a person can get them again and again. Many of these diseases are asymptomatic, which allows them to spread and cause serious complications before a victim is aware of being infected. Finally, some STDs are treatable and some are not.

Syphilis is caused by Treponema pallidum. This bacterium normally infects the penis in males and the vagina or cervix in females, but it can also enter through a cut on the mouth or other parts of the skin. Once inside, the bacteria grow at the site of entry, then spread throughout the body through the lymph and blood vessels. The symptoms of syphilis are caused by the efforts of the immune response of the patient to fight off the infection. The disease occurs in three stages: primary, secondary, and tertiary. In primary syphilis, a flat, firm, painless, red sore called a chancre appears at the site of entry two to ten weeks after infection. Secondary syphilis is characterized by a red rash that appears two to ten weeks after the disappearance of the primary lesion. The rash will disappear in a few weeks. Without treatment, 40 percent of patients will progress to the tertiary stage within three to ten years. Tertiary syphilis is characterized by the formation of severe lesions called gummas on the skin, bones, or internal organs. Gummas on the spinal cord, brain, or heart can lead to seizures, insanity, or death. Almost all pregnant women with untreated primary or secondary syphilis will transmit the bacteria through the placenta to the developing baby, who will develop congenital syphilis. Many babies with congenital syphilis are spontaneously aborted or stillborn. Many others are born with characteristic birth defects, secondary or tertiary syphilis, or neurological damage, and may die shortly after birth.

Gonorrhea is caused by the Neisseria gonorrhoeae bacterium (also known as gonococcus). The bacterium infects the urethra in males and the cervix, vagina, or urethra in females. Most infected males get urethritis (inflammation of the urethra) along with symptoms of a pus-containing discharge from the penis and painful urination. Untreated, 1 percent of these men will develop complications of urethral blockage, epididymitis (inflammation of the epididymis, a sac through which sperm passes as it leaves the testicles), prostatitis (inflammation of the prostate, a gland that secretes fluid for semen), and infertility. Between 20 and 80 percent of women infected with gonococcus are asymptomatic or show only mild symptoms. Symptoms include burning or high frequency of urination, vaginal discharge, fever, and abdominal pain. In 20 to 30 percent of untreated women, gonococcus will spread to the Fallopian tubes and cause pelvic inflammatory disease (PID), which can lead to infertility. Infected mothers can transmit the bacteria to their babies as they pass through the birth canal, causing ophthalmia neonatorum, a type of conjunctivitis (inflammation of the eye) that can cause blindness if untreated.

Most cases of nongonococcal urethritis (NGU) are caused by Chlamydia trachomatis types d through k. This bacterium infects the urethra in males and the cervix or urethra in females. The symptoms of chlamydia infection are often mild and go unnoticed. Males experience mild urethritis with a watery discharge, frequent urination, and painful urination. Females are either asymptomatic or experience mild cervicitis (inflammation of the cervix) or urethritis. Complications include epididymitis in males and PID and infertility in females. Infants born to mothers with cervicitis can develop eye (inclusion conjunctivitis) or lung (infant pneumonia) infections.

Trichomoniasis is caused by the protozoan Trichomonas vaginalis. In both sexes, the disease is often mild or asymptomatic. In males, the organism infects the prostate, seminal vesicles, and urethra. About 10 percent of infected males show signs of mild urethritis, with a thin, white urethral discharge. Secondary bacterial infection can lead to more severe urethritis and inflammation of the prostate and seminal vesicles. In females, the organism can infect the vulva, vagina, and cervix. Females may suffer from severe vaginitis, which includes a tender, red, and itchy genital area, and a profuse, frothy, foul-smelling, greenish-yellow discharge. Newborns may acquire the infection from an infected mother during delivery.

Most genital herpes infections are caused by herpes simplex virus type 2, but some are caused by herpes simplex virus type 1. The virus infects the penis in males and the cervix, vulva, vagina, or perineum in females. Two to seven days after infection, painful blisters appear in the genital area that ulcerate, crust over, and disappear in a few weeks. Herpes viruses are unique in that they can remain latent in the nerves and cause a recurrent infection at any time in the future. Fever, stress, sunlight, or local trauma may trigger the virus to come out of hiding and cause a recurrent infection. The virus can be transmitted from an infected mother to her baby either congenitally, through the placenta, or neonatally, as the baby passes through the birth canal. In congenital or neonatal herpes, the virus can infect all parts of the body, the death rate is high, and survivors commonly have long-term neurological damage and recurrent infections.

Viral hepatitis is also an STD. At least three variants of the virus—hepatitis A virus (HAV), HBV, and HCV—are known to be transmitted sexually. HBV is the form most commonly transmitted sexually. Vaccines are available to immunize persons at risk for HAV and HBV.

Genital warts are caused by human papillomaviruses (HPVs). In males, the warts appear on the penis, anus, and perineum. They are found on the vagina, cervix, perineum, and anus in females. The warts themselves may be removed, but the infection remains for the life of the patient. HPV infection seems to increase a woman’s risk for cervical cancer. Two vaccines for HPV, Gardasil and Cervarix, are now available.

AIDS is caused by the human immunodeficiency virus (HIV). This virus is acquired through sexual contact as well as through intravenous drug use and blood transfusions. HIV infects and inactivates the T helper cells that are needed by the immune system to respond to and fight off infections. Without T helper cells, the immune system eventually becomes nonfunctional, and the affected person becomes susceptible to every type of infection possible. Two-thirds of all AIDS patients get pneumonia caused by Pneumocystis carinii. Other common diseases associated with AIDS patients are tuberculosis and other mycobacterial infections; viral infections such as those caused by cytomegalovirus and herpes viruses; fungal infections; cancers such as Kaposi’s sarcoma; and neurological disorders. HIV can also be transmitted from an infected mother to her baby through the placenta.

Treatment and Therapy

Sexually transmitted diseases can be diagnosed in several ways. One way is by observing the symptoms and case history of the patient. Characteristic sores or symptoms can lead a doctor to suspect a particular disease, and a sample of a scraping from a lesion or an unusual discharge can be examined under a microscope to identify the infecting organism. The syphilis, gonorrhea, chlamydia, and trichomoniasis organisms all have unique shapes that a doctor can recognize. For those STDs with mild symptoms or no symptoms, a doctor can try to grow the organism in the laboratory from samples taken from appropriate sites on the body. All organisms that cause STDs can be grown in the laboratory, and since these organisms are not normally present in humans, isolation of the organism from the body is a sign that the body has been infected by that organism. Finally, there are many blood tests that have been developed to test whether a person has specific antibodies in his or her blood that bind to one of these organisms. The presence of antibodies to an organism implies that one has been or is currently infected with that organism. In many cases, doctors will use several of these methods to confirm a diagnosis of an STD.

Specific treatment recommendations for each sexually transmitted disease are subject to periodic revision. Current recommendations are reviewed by the Centers for Disease Control and are published in the Morbidity and Mortality Weekly Report every three or four years. It is important for physicians to review these recommendations in order to prescribe the best method for treating STDs. All the bacterial and the protozoal STDs can be treated and cured with antibiotics. It is important to seek early diagnosis and treatment of these diseases for three reasons: first, to prevent the disease from spreading; second, to prevent the various complications associated with the diseases; and third, to prevent the infection of infants by pregnant mothers. There is no cure for STDs caused by viruses; there are only drugs that slow the progress of the infection.

Syphilis is commonly treated with penicillin, or alternatively with erythromycin, doxycycline, or ceftriaxone. In most patients receiving appropriate therapy during primary or secondary syphilis, the active disease is totally and permanently arrested. Treatment during the latent stage stops the development of symptoms of the tertiary stage. There is no successful treatment for patients with tertiary syphilis. Cephalosporin antibiotics, such as cefixime and ceftriaxone, have replaced penicillins as therapeutic agents for gonorrhea because of widespread resistance of gonococci to penicillins. Quinolones, such as ciprofloxacin, and azithromycin are other antibiotics that can be effective treatment for gonococcal infections. Doxycycline or azithromycin are used to treat NGU caused by chlamydia, and trichomoniasis is treated with metronidazole or tinidazole.

Genital herpes is treated with antiviral agents such as acyclovir. Topical application of acyclovir is helpful in reducing the duration of primary, but not recurrent, infections. The use of oral acyclovir to suppress recurrent infections may cause more severe and more frequent infections once the therapy has stopped. Neonatal herpes is treated with acyclovir or vidarabine, which can reduce the severity of the infection but cannot reverse any herpes-related neurological damage or prevent recurrent infections. Genital warts can be removed by chemicals, freezing, electrocautery, or laser therapy. Antiviral drugs are useful in treating some STDs: acyclovir for genital herpes, zidovudine for AIDS, and interferon for hepatitis virus. They slow the progress of the disease in some persons, but they do not cure it.

As with any disease, prevention is the most desirable means of controlling STDs. With the exception of viral hepatitis and HPV, there are no vaccines for STDs; although much research is being done and many potential vaccines have been developed and tested, none is yet satisfactory for general and routine use. Therefore, behaviors resulting in disease avoidance are the only means of preventing most STDs. The only 100 percent effective way to prevent a sexually transmitted disease is abstinence. Abstinence means to refrain voluntarily from engaging in sexual activity. Since many of these diseases can be spread through sexual activity other than intercourse, abstinence must include all sexual activity. Choosing to exercise one’s sexuality within a monogamous relationship for life can also help prevent sexually transmitted disease. The use of a condom or any other barrier method can significantly reduce the risk of STD transmission, but is not always effective. Prevention of transmission of STDs from infected mothers to their babies involves early diagnosis and treatment of the mothers before birth and preventive medication of the babies after birth. In the past, ophthalmia neonatorum was the cause of blindness for half of the children admitted to schools for the blind. Therefore, the government made it mandatory to treat all newborns’ eyes with silver nitrate, tetracycline, or erythromycin, to prevent this disease. The instillation of silver nitrate in babies’ eyes does not prevent chlamydia eye infections, so babies born to mothers with chlamydia need additional antibiotic treatment. Prevention of neonatal herpes may involve delivery by cesarean section to avoid infection of the child as it passes through the birth canal. Preventing the spread of AIDS includes screening blood supplies, organ donors, and semen donors and avoiding contact with infected body fluids through sexual contact, blood transfusions, or intravenous drug use.

Control of STDs in a population is complex, since it is both a medical and a social problem. First, it is important that persons who contract a sexually transmitted disease receive early diagnosis and adequate treatment that will prevent further spread of the disease, serious complications, and infection of infants. This is difficult because many STDs are asymptomatic; therefore, people do not know they have the disease and have no reason to seek treatment. Many persons contract STDs from asymptomatic carriers. In addition, social stigma or embarrassment reduces the motivation of a victim to seek prompt medical care. Adequate treatment of STD victims is difficult if they do not want to return for subsequent treatment or will not take all their prescriptions. Finally, people often contract several STDs at the same time, so detection of one STD should routinely instigate testing for other STDs.

Not only does the person with an STD need to be treated, but all the sexual contacts of that person need to be contacted, tested, and treated as well. Public health officials interview victims of STDs to determine the names and addresses of contacts and then try to find and treat the contacts. This is difficult if a victim does not remember who those contacts are, if he or she does not want to discuss his or her sexual activity, or if the contacts do not want to be bothered by the health department. In addition, many private physicians do not report cases of STDs to the public health department; therefore, in many cases, the sources of STDs are never interviewed.

A reduction in risky sexual behavior, such as unprotected sex, would aid in the control of STDs. Effective education to change sexual behavior must be predicated upon the motivation and cognitive development of the student. One-third of all cases involve teenagers and young adults; sexual activity in this age group is on the rise, and members of this group are more likely to have multiple sex partners. Prostitution for money or drugs also increases the incidence of STDs. Other control measures include development of vaccines for these diseases, mandatory reporting of all STDs, and education of the population regarding the dangers and risks involved in acquiring these diseases.

Perspective and Prospects

Syphilis was first recognized at the end of the fifteenth century in Europe, where it rapidly reached epidemic proportions and was called the “great pox.” Gonorrhea was described and given its present name by the Greek physician Galen in 150 CE From the fifteenth century to the eighteenth century, there was much confusion as to the nature of syphilis and gonorrhea, and many persons thought they were different stages of the same disease. In 1767, an English physician named John Hunter inoculated himself with a urethral discharge from a patient with gonorrhea in order to determine once and for all whether they were one disease or two. Unfortunately, that patient also had syphilis, so when Hunter developed symptoms of both gonorrhea and syphilis he concluded they were a single disease. It was not until 1838 that it was clearly proved that they were two separate diseases. Traditionally, 95 percent of all cases of sexually transmitted diseases were either syphilis or gonorrhea. Since the late twentieth century, however, there has been a dramatic increase in the incidence of several other sexually transmitted diseases, such as genital herpes, NGU, AIDS, genital warts, and trichomoniasis.

The rise in incidence of STDs is of epidemic proportions. The World Health Organization reports that in 2008 more than a million people worldwide contracted a sexually transmitted infection (STI) per day and that about 499 million new cases of curable STIs occurred per year. The WHO also reported that in 2011 there were about 34 million people living with HIV around the world; of these more than 8 million people were receiving anti-retroviral therapy (ART) in low- and middle-income nations. The international community set a goal of providing 15 million people with ART by 2015.

In the United States, the Centers for Disease Control and Prevention reported in 2013 that, based on 2008 data, there were a total of 110 million STI cases. About 19.7 million new cases of STIs occur annually, with people between the ages of fifteen and twenty-four accounting for roughly 50 percent of new cases. The direct medical costs related to STIs were estimated to be $16 billion (in 2010 dollars). By 2008, HPV had become the most frequently diagnosed STI in the United States, estimated at more than 14.1 million new cases annually. Other STIs with high incidence included chlamydia (2.86 million new cases annually), trichomoniasis (1.09 million annually), gonorrhea (820,000 new cases annually), and genital herpes (776,000). Because there is no cure for genital herpes, it may be present in 24.1 million Americans. By 2009, there were about 1.1 million people with HIV living in the United States. As of 2010, there were about 47,500 new cases of HIV and 15,500 AIDS-related deaths in the United States. It is estimated that there are 3 to 5 million new cases of NGU per year. One in five couples in the United States is infertile, and much of that infertility is caused by the complications associated with STDs, with chlamydial infection being the primary preventable cause of sterility in women. In the United States, it is estimated that 25 percent of all women are infected with trichomoniasis.

Despite the fact that most STDs can be controlled, the incidence of many of the diseases is still quite high; thus, STDs obviously present a social as well as a medical problem. An increase in education concerning the signs and risks of these diseases, a reduction in unprotected sex, and development of vaccines would help in controlling these destructive and fast-spreading diseases.

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Eng, Thomas Rand, and William T. Butler, eds. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, D.C.: National Academy Press, 1997.

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World Health Organization. Sexually Transmitted Infections (STIs). Geneva, Switzerland: 2013.

Do you think the road the speaker took was really the less travelled one? Why?

No, the road the speaker takes is not really the less traveled one, because, according to the second and third stanzas, there is no road less traveled; they have both been traveled by relatively equal numbers of people.  The speaker says that the second road is "just as fair" as the first road, it just happens to be grassier; however, "the passing there / Had worn them really about the same" (lines 6, 9-10).  The passing there refers to people who have taken these roads before, and, since the roads are worn about the same, we can ascertain that about the same number of people have taken each one.  The roads may look a bit different, but they are equally worn.  In fact, the speaker says that "both that morning equally lay," strewn with leaves that had not yet been trodden black by the steps of others (11).  Therefore, there is no road less traveled because both roads have been taken an approximately equal number of times.