An infection is a condition in which viruses, bacteria, fungi, or parasites enter the body and cause a state of disease. Such invaders are called pathogens. They damage cells of the body by adhering to and damaging the cell walls, releasing toxic substances or causing allergic reactions. The body has a set series of responses to infection, which mostly involve body chemicals, body tissues, and the immune system. It was recently reported that infection is the fourth leading cause of death in the United States and kills more people than cancer and heart disease combined.
Pathogens are everywhere in a person's daily environment: They may enter the body through breathing, ingested food or water, sexual contact, open wounds, or contact with contaminated objects. Having entered the body, pathogens begin to reproduce. Most pathogens are kept in check before they have a chance to multiply. If, however, the body is unable to keep the pathogens in balance, serious disease and even death may occur. Chronic infections may develop if the body has only limited control over a given pathogen. In that case, the infection will have a tendency to flare up in response to stress and weakness. Sepsis is a serious condition in which pathogens spread and circulate throughout the body via the bloodstream. This type of infection affects the entire body.
The body has many natural barriers to infection. For example, the harmless bacteria normally found on the skin, known as commensals, inhibit the growth of many pathogens. Sweat and oil gland secretions also protect the skin; and the skin itself offers a significant physical barrier that no bacteria are able to penetrate. Damage to the skin from burns, insect bites, surgery, or injuries may leave the skin open to infection. In addition to the physical barrier of the skin, many of the body's secretions such as tears, sweat, urine, and saliva contain chemicals that destroy pathogens.
The mucous membranes that line the passageways of the body secrete mucus, which contains enzymes and chemicals that kill or disable pathogens. The pathogens are then trapped in the mucus and filtered out or swallowed. Commensal bacteria also live on the mucous membranes; there they inhibit the spread and multiplication of pathogens just as they do on the skin. The digestive tract contains stomach acid, pancreatic enzymes, and other secretions that protect against infection. Peristalsis and the shedding of the lining of the intestinal tract also help to remove pathogens. The acid pH of the stomach and vagina is protective, as well as the length of the urethra in males. The flushing action of urine and feces as they are excreted also protect against infection.
A fever is defined as the elevation of the body temperature to at least 100°F (37.8°C). Fevers are a helpful part of the body's response to an infection, since most pathogens do not thrive at higher temperatures while the immune system's white blood cells (WBCs) work best in a warm environment. If the fever reaches levels of 102°F (38.9°C) or higher, it may have to be brought down to avoid seizures, dehydration, and tissue damage.
The second level of the body's defenses is the immune system. The white blood cells are a major part of this system. In response to the invasion of pathogens, WBCs are released from the bone marrow into the bloodstream. The main function of these WBCs, depending on their type, is to engulf pathogens and render them harmless, detoxify poisons, produce and release antibodies and chemicals, and clean up wastes left by other WBCs. The spleen, thymus, lymph system, and liver all have roles in the immune response. Successful removal of pathogens from the body often gives immunity against infection by that pathogen in the future.
Pathogens can be persistent. They may secrete enzymes, destroying tissues in the body to spread the infection more quickly and effectively. They may secrete chemicals that counteract the actions of the WBCs. Some pathogens release toxins that kill the surrounding cells. Many also have methods to evade being engulfed and destroyed. In addition, the body's own commensal bacteria may become pathogenic if something upsets their balanced state in the body. This loss of balance may often result from chronic illness, low stomach acid, recurrent use of antibiotics, cross-contamination through medical or sexual exploration, or a compromised immune system.
Infections are caused by pathogens invading the tissues of the body and beginning to multiply. Headaches, muscle aches, fever, chills, and fatigue are common symptoms of infections. Many of these symptoms are due to inflammation and the response of the immune system to the pathogens. For example, during an infection, the blood supply is increased to the affected areas; as the blood rushes to the site of infection, it causes the skin to redden. The blood vessels also become more readily able to release WBCs into the tissues; when the WBCs die and decay they form a thick fluid known as pus. Enzymes released by the WBCs may also be responsible for pain and swelling.
More specific symptoms of infection vary according to the site and type of the infection. Some of these symptoms include:
Risk factors for infections include chronic disease; severe emotional stress; broken skin; changes in the pH of various body fluids; malnutrition; surgery; rupture of amniotic membranes; invasive medical or dental procedures; tissue injuries or destruction; decreased flow of body fluids; changes in peristalsis; decreased output of stomach acid; recurrent use of antibiotics; and suppressed immune function. Many infections have a high probability of being passed from person to person. This is especially true of respiratory diseases, which can be transmitted through contact with the sputum and droplets produced by coughing or sneezing. Contact with infected waste products, open sores, skin eruptions, infected clothing and bedclothes, and sexual contact are circumstances which often lead to the further spread of infections.
New concerns about infections continue to baffle researchers and clinicians into the twenty-first century. First, the world faces the threat of infection from bioterrorism, and Americans faced a scare from deliberate distribution of anthrax spores through the United States postal system following the September 11, 2001, terrorist attack. The year 1999 saw the first reports of the West Nile virus in the United States, and reported cases of the disease began spreading after that date. Further, clinicians worry about widespread antibiotic resistance, as individuals and the public at large become exposed to more antibiotics for longer periods of time.
Many infections are minor and self-limiting. Some infections, however, are serious; some can even lead to permanent impairment or death. If an infection does not clear up within a few days, or if it gets worse, a healthcare provider should be consulted. Infections are initially diagnosed by the patient's presentation and by a history of the illness or injury and the symptoms.
A complete blood count (CBC) is a simple clinical test that can be used to diagnose an infection. Increases in the total WBC count usually indicate a bacterial infection; decreases tend to indicate a viral infection or a very severe infection, both of which may cause the destruction of WBCs faster than they can be produced. Increases in specific types of white blood cells known as neutrophils, lymphocytes, and monocytes also point to an infection. An increase in eosinophils may be due to a parasitic infection. A blood chemistry panel may be taken to determine whether there are chemical changes that may have been brought on by an infection.
A serious illness may require further evaluation and diagnostic tests. Additional laboratory tests can be performed using blood, feces, or samples of the infected tissue. Ultrasound, computed tomography (CT) scans, and magnetic resonance imaging (MRI) may also be used. In some cases, a tissue sample (biopsy) is taken from the affected site for microbial culture tests and microscopic examination.
Echinacea spp. enhances the action of the immune system. It can be taken for up to six weeks to prevent or heal infections. Goldenseal (Hydrastis canadensis) has strong antibiotic qualities. Garlic (Allium sativum) is also antibiotic. Licorice (Glycyrrhiza glabra) has significant antiviral activity. It reduces the bad effects of stress on the health, and has been used to treat herpes, staphylococcal and streptococcal infections, typhus, cholera, pneumonia, and infections caused by Candida albicans. Astragalus membranaceus is a Chinese herb that may be used to enhance the immune system as well as to prevent the recurrence of chronic infections. Pau d'arco (Tabebuia impetiginosa) is recommended for internal fungal infections, while the topical use of tea tree oil (Melaleuca alternfolia) is recommended for some external infections.
A healthful balanced diet and lifestyle are important supports of the immune function. Reishi (Ganoderma lucidum), shiitake (Lentinus edodes), and maitake (Grifola frondosa) mushrooms are renowned for their ability to strengthen the immune system and their antimicrobial properties. Regular supplementation with vitamin C, vitamin A or beta-carotene, zinc, and bioflavonoids is also recommended to boost the immune response.
Sugary foods, including honey, may depress the immune system. Very high levels of fat in the diet may also interfere. Alcohol decreases the functioning of the immune system. All of these substances should be avoided during the course of an infection. Food allergies should be considered, especially in the case of chronic colds, throat infections, and ear infections. Once allergens have been identified, they should be avoided. Patients should increase their intake of fluids, including soups, teas, diluted fruit and vegetable juices, and pure water.
Aromatherapy may be a useful supportive measure in infectious conditions. An essential oil of cedarwood (Cedrus atlantica) is recommended in fungal infections; essential oils of tea tree (Melaleuca alternifolia) and patchouli are also recommended. It should be remembered, however, that essential oils are very concentrated, toxic to the liver and kidneys, and should be used only in very small doses (drops).
Acupuncture is helpful in stimulating the immune system. It reduces the effects of stress, improves circulation, and increases the production of RBCs and WBCs. It has been used for thousands of years to treat infectious diseases.
Constitutional hydrotherapy is the use of applications of hot water alternated with cold. It is effective in respiratory infections and in stimulating the immune system. For proper administration of hydrotherapy, a naturopath or other healthcare provider familiar with its techniques should be consulted.
Minor infections are often relieved by over-the-counter medications. A high fever or joint pain may be a sign of an infection spreading throughout the body. A physician should be contacted. Infections from bites and puncture wounds should also receive medical attention and possibly a tetanus injection.
Serious infections may be treated with antibiotics. Antibiotics are effective against many parasitic and fungal infections as well as bacteria. Antibiotics may also be given during a viral infection even though they have no effect on viruses. This measure is taken to prevent bacterial infections, which may occur due to the weakened state brought on by the virus. In the case of viral infections, antiviral drugs are used to reduce symptoms. Their usefulness, however, is limited because viruses quickly mutate and develop resistance to them.
Antifungal drugs are often applied directly to fungal infections. They may be taken orally, applied topically, or injected. Fungal infections often require several weeks of treatment and repeated courses of the drug. Both antifungal and antiviral drugs tend to be somewhat toxic to people as well as to the pathogens.
Most minor infections resolve within a week. Chronic infections may last for years. Serious infections need to be attended by a physician, as tissue damage and death may be an imminent outcome. Anemia may result from severe infections, since RBCs or their production may be affected.
Various vaccines are available to prevent major infections. These vaccines are made from deactivated parts of viruses or bacteria that confer future immunity to infection by those pathogens. Vaccinations for mumps, measles, chicken pox, tetanus, hepatitis, diphtheria, whooping cough, and pneumonia are widely available in the United States. They are routinely given to infants and children to provide lifetime immunity from these diseases. An anthrax vaccine is available but as of early 2002, reports say that a new, improved vaccine is needed in the United States, since the vaccine requires six doses over 18 months for full protection, with a booster every 12 months.
Good hygienic practices should be maintained. They include keeping the body clean as well as keeping food, utensils, and areas of preparation clean and free of contamination. Meat, seafood, and dairy products should be properly refrigerated. Breaks in the skin should be cleaned and disinfected to avoid further infection. Direct contact with people known or suspected to have infections should be limited, depending on the nature of the disease.
The health of the immune system should be maintained. A positive mental outlook is important, together with appropriate amounts of sleep, relaxation, and stress reduction. A healthful diet should be followed, with decreased sugar, salt, saturated fats, and chemical additives. Good lifestyle habits, such as giving up smoking and taking regular physical exercise, should be cultivated.
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Teresa G. Odle