6. Viral infections
A virus is a small infectious organism—much smaller than a fungus or bacterium—that must invade a living cell to reproduce (replicate). The virus attaches to a cell (called the host cell), enters it, and releases its DNA or RNA inside the cell. The virus's DNA or RNA is the genetic material containing the information needed to replicate the virus. The virus's genetic material takes control of the cell and forces it to replicate the virus. The infected cell usually dies because the virus keeps it from performing its normal functions. When it dies, the cell releases new viruses, which go on to infect other cells.
Some viruses do not kill the cells they infect but instead alter the cell's functions. Sometimes the infected cell loses control over normal cell division and becomes cancerous. Some viruses leave their genetic material in the host cell, where the material remains dormant for an extended time (latent infection). When the cell is disturbed, the virus may begin replicating again and cause disease.
Viruses usually infect one particular type of cell. For example, cold viruses infect only cells of the upper respiratory tract. Additionally, most viruses infect only a few species of plants or animals. Some infect only people. Many viruses commonly infect infants and children .
Viruses are spread (transmitted) in various ways. Some are swallowed, some are inhaled, and some are spread by the bites of insects and other parasites (for example, mosquitoes and ticks). Some are spread sexually.
Defenses: The body has a number of defenses against viruses. Physical barriers, such as the skin, discourage easy entry. Infected cells also make interferons, substances that can make uninfected cells more resistant to infection by many viruses.
When a virus enters the body, it triggers the body's immune defenses. These defenses begin with white blood cells, such as lymphocytes and monocytes, which learn to attack and destroy the virus or the cells it has infected. If the body survives the virus attack, some of the white blood cells remember the invader and are able to respond more quickly and effectively to a subsequent infection by the same virus. This response is called immunity. Immunity can also be produced by getting a vaccine.
Types of Viral Infections: Probably the most common viral infections are those of the nose, throat, and upper airways (upper respiratory infections). These infections include sore throat, sinusitis, and the common cold. Influenza is a viral respiratory infection. In small children, viruses also commonly cause croup and inflammation of the windpipe (laryngotracheobronchitis) or other airways deeper inside the lungs. Respiratory infections are more likely to cause severe symptoms in infants, older people, and people with a lung or heart disorder.
Some viruses (such as rabies, West Nile virus, and several different encephalitis viruses) infect the nervous system. Viral infections also develop in the skin, sometimes resulting in warts or other blemishes.
Other common viral infections are caused by herpesviruses. Eight different herpesviruses infect people. Three of them—herpes simplex virus type 1, herpes simplex virus type 2, and varicella-zoster virus—cause infections that produce blisters on the skin or mucus membranes. Another herpesvirus, Epstein-Barr virus, causes infectious mononucleosis. Cytomegalovirus is a cause of serious infections in newborns and in people with a weakened immune system. It can also produce symptoms similar to infectious mononucleosis in people with a healthy immune system. Human herpesviruses 6 and 7 cause a childhood infection called roseola infantum. Human herpesvirus 8 has been implicated as a cause of cancer (Kaposi's sarcoma) in people with AIDS.
All of the herpesviruses cause lifelong infection because the virus remains within its host cell in a dormant (latent) state. Sometimes the virus reactivates and produces further episodes of disease. Reactivation may occur rapidly or many years after the initial infection.
Diagnosis
Common viral infections may be diagnosed based on symptoms. For infections that occur in epidemics (such as influenza), the presence of other similar cases may help doctors identify a particular infection. For other infections, blood tests and cultures (growing microorganisms in the laboratory from samples of blood, body fluid, or other material taken from an infected area) may be done. Blood may be tested for antibodies to viruses or for antigens (proteins on or in viruses that trigger the body's defenses). Polymerase chain reaction (PCR) techniques may be used to make many copies of the viral genetic material, enabling doctors to rapidly and accurately identify the virus. Tests are sometimes done quickly—for instance, when the infection is a serious threat to public health or when symptoms are severe. A sample of blood or other tissues is sometimes examined with an electron microscope, which provides high magnification with clear resolution.
Treatment
Drugs that combat viral infections are called antiviral drugs. Many antiviral drugs work by interfering with replication of viruses. Most drugs used to treat human immunodeficiency virus (HIV) infection work this way. Because viruses are tiny and replicate inside cells using the cells' own metabolic functions, there are only a limited number of metabolic functions that antiviral drugs can target. In contrast, bacteria are relatively large organisms, commonly reproduce by themselves outside of cells, and have many metabolic functions that antibacterial drugs (antibiotics) can target. Therefore, antiviral drugs are much more difficult to develop than antibacterial drugs. Antiviral drugs can be toxic to human cells. Viruses can develop resistance to antiviral drugs.
Other antiviral drugs strengthen the immune response to the viral infection. These drugs include several types of interferons, immunoglobulins, and vaccines. Interferon drugs are replicas of naturally occurring substances that slow or stop viral replication. Immune globulin is a sterilized solution of antibodies (also called immunoglobulins) collected from a group of people. Vaccines are materials that help prevent infection by stimulating the body's natural defense mechanisms. Many immune globulins and vaccines are given before exposure to a virus to prevent infection. Some immune globulins and some vaccines, such as those for rabies and hepatitis B, are also used after exposure to the virus to help prevent infection from developing or reduce the severity of infection. Immune globulins may also help treat some established infections and also prevent infection after future exposures to the virus.
Most antiviral drugs can be given by mouth. Some can also be given by injection into a vein (intravenously) or muscle (intramuscularly). Some are applied as ointments, creams, or eye drops or are inhaled as a powder.
Antibiotics are not effective against viral infections, but if a person has a bacterial infection in addition to a viral infection, an antibiotic is often necessary.
Notes:
host cell клетка “хозяина”
latent infection скрытая инфекция
replicate повторять
Varicella-zoster virus вирус опоясывающего лишая
Epstein-Barr-virus Энштейна-Барр вирус, цитомегаловирус
Roseola infantum детская розеола, внезапная экзантема
trigger провоцировать
Kaposi’s sarcoma Капоши ангиоматоз
Text A Herpes simplex
Herpes simplex virus infection causes recurring episodes of small, painful, fluid-filled blisters on the skin, mouth, lips (cold sores), eyes, or genitals.
There are two types of herpes simplex virus (HSV): HSV-1 and HSV-2. HSV-1 is the usual cause of cold sores on the lips (herpes labialis and sores on the cornea of the eye (herpes simplex keratitis). HSV-2 is the usual cause of genital herpes. This distinction is not absolute: genital infections are sometimes caused by HSV-1. Infection also can occur in other parts of the body such as the brain (a serious illness) or gastrointestinal tract. Widespread infection may occur in newborns or in people with a weakened immune system.
HSV is very contagious and can be spread by direct contact with sores and sometimes by contact with the oral and genital areas of people with chronic HSV infection who are between episodes of sores.
HSV infections produce an eruption of tiny blisters. The first eruption is called primary herpes. After the eruption of blisters subsides, the virus remains in a dormant (latent) state inside the collection of nerve cells (ganglia) near the spinal cord that supply the nerve fibers to the infected area. Periodically, the virus reactivates, begins growing again, and travels through the nerve fibers back to the skin—causing eruptions of blisters in the same area of skin as the earlier infection. Sometimes the virus is present on the skin or mucous membranes even when no blisters can be seen.
The virus may reactivate many times. Reactivation of a latent oral or genital HSV infection may be triggered by a fever, menstruation, emotional stress, or suppression of the immune system (for example, by a drug taken to prevent rejection of an organ transplant). An episode of cold sores can develop after physical trauma, such as a dental procedure or overexposure of the lips to sunlight. Often, the trigger is unknown.
Symptoms and Complications
An eruption of tiny blisters appears on the skin or on the mucous membranes, such as those lining the eyes, vagina, cervix, or inside of the mouth. The skin around the blisters is often red.
Oral Infection: The first oral infection with HSV usually causes multiple painful sores inside the mouth (herpetic gingivostomatitis). In addition, people usually feel sick and have a fever, a headache, and body aches. The mouth sores last 10 to 14 days and are often very severe, making eating and drinking extremely uncomfortable. In some first oral infections, swollen gums are the only symptom. Occasionally, no symptoms develop. Herpetic gingivostomatitis most commonly develops in Unlike the first oral infection , recurrences usually produce only a single sore. The sore is called a cold sore or fever blister (so named because they are often triggered by colds or fevers). Other triggers include sunburn on the lips, certain foods, anxiety, certain dental procedures, and any condition that reduces the body's resistance to infection. If people have a cold sore, they should postpone dental visits until the sore heals.
Cold sores typically develop on the lips. Before a cold sore appears, people usually feel a tingling at the site, lasting from minutes to a few hours, followed by redness and swelling. Usually, fluid-filled blisters form and break open, leaving sores. The sores quickly form a scab. After about a week, the scab falls off and the episode ends. Less often, tingling and redness occur without blister formation. Sometimes small clusters of sores develop on the gums or the roof of the mouth. These sores also last about a week and then go away.
Genital Infection: The first genital HSV infection (genital herpes) can be severe and prolonged, with multiple painful blisters in the genital area. Fever and a general feeling of illness (malaise) are common, and some people have burning during urination, difficulty urinating, or pain during defecation. Some people have no symptoms.
Recurrences of genital herpes begin with symptoms (including local tingling, discomfort, itching, or aching in the groin) that precede the blisters by several hours to 2 to 3 days. Painful blisters surrounded by a reddish rim appear on the skin or mucous membranes of the genitals. The blisters quickly break open, leaving sores. Blisters may also appear on the thighs or buttocks or around the anus. In women, blisters may develop on the vulva. These blisters are usually obvious and very painful. Internal blisters may develop in the vagina or on the cervix. They are less painful and are not visible. A typical episode of recurring genital herpes lasts a week.
Bacteria sometimes infect genital sores due to HSV infection. Such sores may appear more irritated or have a thick or foul-smelling discharge
Other Infections and Complications: In people with a weakened immune system, recurrences of oral or genital herpes can result in progressive, gradually enlarging sores that take weeks to heal. The infection may progress inside the body, moving down into the esophagus and lungs or up into the colon. Ulcers in the esophagus cause pain during swallowing, and infection of lungs causes pneumonia with cough and shortness of breath.
Sometimes HSV-1 or HSV-2 enters through a break in the skin of a finger, causing a swollen, painful, red fingertip (herpetic whitlow). Health care workers who are exposed to saliva or other body secretions (such as dentists) when not wearing gloves are most commonly affected.
HSV-1 can infect the cornea of the eye. This infection (called herpes simplex keratitis) causes a painful sore, tearing, sensitivity to light, and blurred vision. Over time, particularly without treatment, the cornea can become cloudy, causing a significant loss of vision and requiring corneal transplantation.
Infants or adults with a skin disorder called atopic eczema can develop a potentially fatal HSV infection in the area of skin that has the eczema (eczema herpeticum). Therefore, people with atopic eczema should avoid being near anyone with an active herpes infection.
HSV can infect the brain. This infection (called herpes encephalitis) begins with confusion, fever, and seizures and can be fatal.
Infrequently, a pregnant woman can transmit HSV infection to her baby (called neonatal herpes). Transmission usually occurs at birth, when the baby comes into contact with infected secretions in the birth canal. Rarely, HSV is transmitted to the fetus during pregnancy. Transmission during birth is more likely when the mother has recently acquired the herpes infection and when the mother has visible herpes sores in the vaginal area, although babies may become infected from mothers who have no apparent sores. When acquired at birth, the infection appears between the 1st and 4th week of life. Newborns with HSV infection become very ill. They may have widespread disease, brain infection, or skin infection. Without treatment, two thirds die, and even with treatment, many have brain damage.
Diagnosis
HSV infection is usually easy for doctors to recognize. If unsure, doctors may use a swab to take a sample of material from the sore and send the swab to a laboratory to grow (culture) and identify the virus. Sometimes doctors examine material scraped from the blisters under a microscope. Although the virus itself cannot be seen, scrapings sometimes contain enlarged infected cells (giant cells) that are characteristic of infection by a herpes-type virus. Blood tests to identify antibodies to HSV and biopsy of the sores can also be helpful. Certain blood tests can distinguish between HSV-1 infection and HSV-2 infection. This information helps doctors determine the risk of transmission, for example, to sex partners.
If a brain infection is suspected, magnetic resonance imaging (MRI) or computed tomography (CT) of the brain, and a spinal tap (lumbar puncture) to obtain a sample of cerebrospinal fluid, may be done.
Treatment
Antiviral Drugs: No current antiviral treatments can eradicate HSV infection, and treatment of a first oral or genital infection does not prevent chronic infection of nerves. However, during recurrences, antiviral drugs, such as zovirax, valtrex, or famvir, may relieve discomfort slightly and help symptoms resolve a day or two sooner. Treatment is most effective if started early, usually within a few hours after symptoms start—preferably at the first sign of tingling or discomfort, before blisters appear. For people who have frequent, painful attacks, the number of outbreaks can be reduced by continuous therapy (suppression) with antiviral drugs. Antiviral drugs are available by prescription only.
Penciclovir (denavir) cream, applied every 2 hours during waking hours, can shorten the healing time and duration of symptoms of a cold sore by about a day. Nonprescription creams containing docosanol (abreva) (applied 5 times a day) may provide some relief. Acyclovir (zovirax), valacyclovir (valtrex), or famciclovir (famvir) taken by mouth for a few days may be the most effective treatment.
Severe HSV infections, including herpes encephalitis and infections in newborns, are treated with intravenous acyclovir (zovirax). If the virus becomes resistant to acyclovir (zovirax), foscarnet (foscavir) can be given.
People with herpes simplex keratitis are usually given trifluridine (viroptic) eye drops. An ophthalmologist should supervise treatment.
Other Treatments: For people who have minimal discomfort, the only treatment needed for recurring herpes of the lips or genitals is to keep the infected area clean by gentle washing with soap and water. Applying ice may be soothing and reduce swelling.
Applying prescription or nonprescription topical anesthetics, such as tetracaine cream or benzocaine ointment, may help relieve pain. If the mouth contains many sores, the mouth can be rinsed with lidocaine, which should not be swallowed. Topical anesthetics should be used only about once every few hours. If used more often, these drugs can have harmful side effects.
Pain relievers may be taken for pain.
Prevention
People should avoid activities and foods known to trigger recurrences. For example, they should avoid exposure to sunlight as much as possible.
Because HSV infection is contagious, people with infection of the lips should avoid kissing as soon as they feel the first tingling (or, if no tingling is felt, when a blister appears) until the sore has completely healed. They should not share a drinking glass and, if possible, should not touch their lips. They should also avoid oral sex. People with genital herpes should use condoms at all times. Even when there are no visible blisters and no symptoms, the virus may be present on the genitals and can be spread to sex partners. Vaccines for the prevention of HSV infections are being developed.
Notes:
herpes simplex простой герпес, герпетическая лихорадка
herpetic gingivostomatitis герпетический гингивостоматитa
defecation опоражнение кишечника
postpone откладывать
recurrence рецидив
buttocks ягодицы
move down спускаться, опускаться вниз
move up продвигаться вперед или выше
Text B Common cold
The common cold is a viral infection of the lining of the nose, sinuses, throat, and large airways
Common colds are among the most common illnesses. Many different viruses cause colds, but rhinoviruses (of which there are 100 subtypes) are implicated more often than others. Colds caused by rhinoviruses occur more commonly in the spring and fall. Different viruses cause colds during other times of the year.
Colds spread mainly when people's hands come in contact with nasal secretions from an infected person. These secretions contain cold viruses. When people then touch their mouth, nose, or eyes, the viruses gain entry to the body and cause a cold. Less often, colds are spread when people breathe air containing droplets that were coughed or sneezed out by an infected person. A cold is most contagious during the first 1 or 2 days after symptoms develop. Becoming chilled does not cause colds, nor does it increase a person's susceptibility to infection. General health and eating habits also do not seem to affect susceptibility to infection, nor does having an abnormality of the nose or throat (such as enlarged tonsils or adenoids).
Symptoms and Diagnosis
Symptoms start 1 to 3 days after infection. Usually, the first symptom is a scratchy or sore throat or discomfort in the nose. Later, people start sneezing, have a runny nose, and feel mildly ill. Fever is not common, but a mild fever may occur at the beginning of the cold. At first, secretions from the nose are watery and clear and can be annoyingly plentiful, but eventually, they become thicker, opaque, yellow-green, and less plentiful. Many people also develop a mild cough. Symptoms usually disappear in 4 to 10 days, although the cough often lasts into the second week.
Complications may prolong the disease. Rhinovirus infection often triggers asthma attacks in people with asthma. Some people develop bacterial infections of the middle ear (otitis media) or sinuses. These infections develop because congestion in the nose blocks the normal drainage of those areas, allowing bacteria to grow in collections of blocked secretions. Other people develop bacterial infections of the lower airways (secondary bronchitis or pneumonia).
Doctors are usually able to diagnose a cold based on the typical symptoms. A high fever, severe headache, rash, difficulty breathing, or chest pain suggests that the infection is not a simple cold. Laboratory tests are not usually needed to diagnose a cold. If complications are suspected, doctors may order blood tests and x-rays.
Prevention
Because so many different viruses cause colds and because each virus changes slightly over time, an effective vaccine has not yet been developed. The best preventive measure is practicing good hygiene. Because many cold viruses are spread through contact with the secretions of an infected person, people with cold symptoms and people in their household and office should wash their hands frequently. Sneezing and coughing should be done into tissues, which should be carefully disposed of. When possible, people with symptoms should sleep in a separate room. People who are coughing or sneezing because of a cold should not go to work or school where they might infect others. Cleaning shared objects and surfaces with a disinfectant can also help to reduce the spread of common cold viruses.
Despite their popularity, echinacea and high-dose vitamin C (up to 2,000 milligrams per day) have not been shown to prevent colds.
Treatment
People with a cold should stay warm and comfortable and try to avoid spreading the infection to others. Anyone with a fever or severe symptoms should rest at home. Drinking fluids and inhaling steam or mist from a vaporizer may help to keep secretions loose and easier to expel.
Currently available antiviral drugs are not effective against colds. Antibiotics do not help people with colds, even when the nose or cough produces thick or colored mucus.
Echinacea, zinc preparations, and vitamin C have been suggested as treatment. Some small studies have shown them to be effective. Others have shown them to be ineffective. But no well-designed, large clinical studies have confirmed their effectiveness. Thus, most experts do not recommend them as treatment.
Several popular nonprescription (over-the-counter) remedies help relieve cold symptoms. Because they do not cure the infection, which usually resolves after a week regardless of treatments tried, doctors feel that their use is optional, depending on how bad the person feels. Several different types of drugs are used:
Decongestants, which help open clogged nasal passages
Antihistamines, which help dry a runny nose
Cough syrups, which may make coughing easier by thinning secretions or suppressing cough.
These drugs are most often sold as combinations but can also be obtained individually. For relieving nasal congestion, inhaled decongestants are better than forms taken by mouth. However, taking inhaled forms for more than 3 to 5 days, then stopping, may make congestion worse than it was originally. Ipratropium, a nasal spray available only by prescription, also helps dry a runny nose. Older antihistamines, such as chlorpheniramine , can cause drowsiness. Newer antihistamines, available only by prescription, are less likely to cause drowsiness but are ineffective for treating the common cold. Nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin, ibuprofen , and naproxen , can relieve aches and pains and reduce fever, as can acetaminophen. Aspirin is generally not recommended for children because, in children, it increases the risk of Reye's syndrome. Cough suppressants are not routinely recommended because coughing is a good way to clear secretions and debris from the airways during a viral infection. However, a severe cough that interferes with sleep or causes great discomfort can be treated with a cough suppressant.
Notes:
rhinovirus infection риновирусная инфекция
otitis meadia отит среднего уха
decongestant drug противоотечное лекарственное средство
Reye’s syndrome гепатоцеребральный синдром, Рейе синдром
opaque темный, непрозрачный
expel удалять
Text C Influenza
Influenza (flu) is infection of the lungs and airways with one of the influenza viruses. It causes a fever, runny nose, sore throat, cough, headache, muscle aches (myalgias), and a general feeling of illness (malaise).
Every year, throughout the world, widespread outbreaks of influenza occur during late fall or early winter. Influenza occurs in epidemics, in which many people get sick all at once. Influenza epidemics may occur in two waves: first in schoolchildren and the people who live with them and, second, in people who are confined to home or live in long-term care facilities, mainly older people. In each epidemic, usually only one strain of influenza virus is responsible for the disease. The name of a strain often reflects where it was first found: a location (for example, Hong Kong flu) or an animal (for example, swine flu).
There are two types of influenza virus, type A and type B, and many different strains within each type. About 95% of influenza cases are caused by influenza virus type A. The illnesses produced by the different types and strains are similar. The strain of influenza virus causing outbreaks is always changing, so each year the influenza virus is a little different from the previous years. It often changes enough that previously effective vaccines no longer work.
Influenza is distinctly different from the common cold. It is caused by a different virus and produces symptoms that are more severe. Also, influenza affects cells much deeper down in the respiratory tract.
Influenza virus is spread by inhaling droplets that have been coughed or sneezed out by an infected person or by having direct contact with an infected person's nasal secretions. Handling household articles that have been in contact with an infected person or an infected person's secretions may sometimes spread the disease.
Symptoms and Diagnosis
Symptoms start 1 to 4 days after infection and can begin suddenly. Chills or a chilly sensation is often the first indication. Fever is common during the first few days, sometimes reaching 102 to 103° F (about 39° C). Many people feel so ill, weak, and tired that they remain in bed for days. They have aches and pains throughout the body, particularly in the back and legs. Headache is often severe, with aching around and behind the eyes. Bright light may make the headache worse.
At first, respiratory symptoms may be relatively mild. They may include a scratchy sore throat, a burning sensation in the chest, a dry cough, and a runny nose. Later, the cough can become severe and bring up phlegm (sputum). The skin may be warm and flushed, especially on the face. The mouth and throat may redden, the eyes may water, and the whites of the eyes may become bloodshot. People, especially children, may have nausea and vomiting. A few people lose their sense of smell for a few days or weeks. Rarely, the loss is permanent.
Most symptoms subside after 2 or 3 days. However, fever sometimes lasts up to 5 days. Cough, weakness, sweating, and fatigue may persist for several days or occasionally weeks. Mild airway irritation, which can result in a decrease in how long or hard a person can exercise, or slight wheezing may take 6 to 8 weeks to completely resolve.
The most common complication of influenza is pneumonia, which can be viral, bacterial, or both. In viral pneumonia, the influenza virus itself spreads into the lungs. In bacterial pneumonia, unrelated bacteria (such as pneumococci or staphylococci) attack the person's weakened defenses. With either, people may have a worsened cough, difficulty breathing, persistent or recurring fever, and sometimes blood or pus in the sputum. Pneumonia is more common among older people and among people with a heart or lung disorder. In long-term care facilities, as many as 7% of older people who develop influenza have to be hospitalized, and 1 to 4% die. Younger people with a chronic disorder are also at risk of developing severe complications.
Because most people are familiar with the symptoms of influenza and because influenza occurs in epidemics, it is often correctly diagnosed by the person who has it or by family members. The severity of symptoms and the presence of a high fever and body aches help distinguish influenza from a cold, especially when the illness occurs during an influenza outbreak. It is more difficult to correctly identify influenza by symptoms alone when no outbreak is occurring. Tests on samples of blood or respiratory secretions can be used to identify the influenza virus. Such tests are done mainly when people appear very ill or when a doctor suspects another cause for the symptoms. Some tests can be done in the doctor's office.
Prevention
Annual vaccination is the best way to avoid getting influenza. Influenza vaccines contain inactivated (killed) influenza virus or pieces of the virus and are given by injection. A newer vaccine, inhaled as a nasal spray, contains weakened live viruses. This vaccine is used only in healthy people aged 5 to 49 years. Influenza vaccines usually protect against three different strains of influenza virus. Different vaccines may be given every year to keep up with changes in the virus. Doctors try to predict the strain of virus that will attack each year based on the strain of virus that predominated during the previous influenza season and the strain causing disease in other parts of the world.
Vaccination is useful for most people but is particularly important for people who are likely to become very ill if infected. These people include the young (particularly those younger than 24 months), those older than 65, those with a weakened immune system, and those with a chronic disorder such as diabetes or a lung, heart, or kidney disorder. In older people who live in long-term care facilities, the vaccine is less likely to prevent influenza, but it reduces the chances of developing pneumonia and of dying. Other than occasional soreness at the injection site, side effects from the vaccine are rare.
Several antiviral drugs can be used to prevent infection with influenza virus. Doctors may prescribe these drugs when people have had a clear, recent exposure to someone with influenza. These drugs are also given to people who have conditions that make vaccination ineffective or dangerous. The drugs are used during epidemics of influenza to protect unvaccinated people who are at high risk of complications of influenza: older people and people with a chronic disorder. Amantadine and rimantadine are older antiviral drugs that provide protection against influenza type A but not influenza type B. These drugs can cause stomach upset, nervousness, sleeplessness, and other side effects, especially in older people and in those with a brain or kidney disorder. Rimantadine tends to have fewer side effects than amantadine. Another drawback of both amantadine and rimantadine is that the influenza virus rapidly develops resistance to them. During the 2005 to 2006 influenza season, concerns about resistance prompted the Centers for Disease Control and Prevention to discourage the use of these drugs for prevention and treatment. Two newer drugs, oseltamivir and zanamivir, can prevent infection with influenza virus type A or type B. These drugs have minimal side effects.
Treatment
The main treatment for influenza is to rest adequately, drink plenty of fluids, and avoid exertion. Normal activities may resume 24 to 48 hours after the body temperature returns to normal, but most people take several more days to recover. People may treat fever and aches with acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs, such as aspirinor ibuprofen). Because of the risk of Reye's syndrome, children should not be given aspirin. Acetaminophen and ibuprofen can be used in children if needed. Other measures as listed for the common cold, such as nasal decongestants and steam inhalation, may help relieve symptoms.The same antiviral drugs that prevent infection (amantadine, rimantadine, oseltamivir, and zanamivir) are also helpful in treating people who have influenza. However, these drugs work only if taken in the first day or two after symptoms begin, and they shorten the duration of fever and respiratory symptoms only by a day or so. Nevertheless, these drugs are very effective in some people. Most doctors recommend zanamivir or oseltamivir, which are effective against both influenza type A and type B. If a secondary bacterial infection develops, antibiotics are added.
Notes:
bring up phlegm откашлять макроту
be confined to home не выходить из дома по болезни
outbreak вспышка(эпидемии)
keep up with быть хорошо осведоленным о чем-либо
drawback отрицательная сторона, недостаток
EXERCISES
Exercise 1. Make up sentences of your own using the following words and phrases from the section “Abscesses.”
An accumulation of pus, the location of the abscess, abscess develop anywhere in the body, to heal an abscess without treatment, to drain a large abscess, to select the most effective antibiotic, abdominal abscess, an abscess below the diaphragm, abscesses in the midabdomen, pelvic abscesses, abscesses in the kidney , abscesses in the spleen, liver abscess.
Exercise 2. Study the texts from the section “Bacillary infections” and say whether these statements are right or wrong. Correct them, if they are wrong.
Several groups of bacteria can form structures called endospores or spores.
Anthrax is not transmitted by spores- a vegetative reproductive form of the bacteria.
Early and aggressive treatment with antibiotics, vaccination against anthrax should be administered before completing antimicrobial therapy.
Brucella is a genus of Gram-negative aerobic spherical or rodlike parasitic bacteria responsible for Cat-scratch-disease in man.
Untreated brucellosis may last for years but prolonged administration of tetracycline antibiotics or streptomycin is effective.
Many bacterial species are beneficial.
Bartonella henselae make a cat sick, and kittens or cats carry the bacteria for months.
Once a cat is infected, the bacteria doesn’t live in the animal saliva during life.
In most children and adolescents, swollen lymph nodes are the main symptoms of brucellosis and the illness often is mild.
Gram-negative bacteria retain the initial stain, appearing violet microscopically.
Gram-positive bacteria lose the initial stain but take up the counterstain, so that they appear red microscopically.
Bacillus- any red-shaped bacterium.
Untreated anthrax can’t be fatal.
Bacillus anthracis is transmitted to man by contact with animal hair, hides or excrement.
Harmful bacteria doesn’t penetrate the body’s defenses.
Exercise 3. The words on the right can be used to form a noun that fits suitably in the blank space. Fill each blank in this way.
An injury, including an invasion by bacteria causes___ (to inflame).
Inflammation partly serves to direct certain defense mechanisms to the site of injury or ____ . (to infect)
____ by most microorganisms begins when they adhere to a person’s cells. (to invade)
A serious infection may cause ___ ulcers in the upper intestine, leading to bleeding. (to stress)
The ___ of equipment is necessary to kill spores. (to sterile)
Some disease organisms may trigger the inflammatory ___ in the body. (to respond)
In the most European countries, ___ against many childhood diseases is available. (to vaccinate)
In the case of mumps the period of ___ is very long. (to incubate)
Although the vaccine probably provides lifetime ___ , people at high risk are advised to receive the vaccine every six years. (to protect)
A doctor weighs the _____ of the side effect against the ___ of the infection. (to be serious)
Exercise 4. Study the texts from the sections “ bacillary, coccal, fungal, viral infections” and compare their etiology. Give your own example of diseases to each type of infections and tell about them in details.
Exercise 5. Arrange a discussion on the text “Tuberculosis (TB)”.
What is TB?
Is it contagious?
What bacteria can Tuberculosis cause?
Is TB characterized by a lifelong balance between the host and rod-shaped bacteria?
Are symptoms of Tuberculosis vague and difficult to identify?
What types of TB do you know? Define each.
What diagnostic method should a doctor choose to recognize an illness?
Can TB affect organs of the body: bladder, brain, pericardium, joints, kidney, spine?
Does a tuberculin skin test identify all types of present TB?
What complication can it give ?
Is it truth, that BCG (bacilli Calmette-Guerin) vaccine can prevent such serious disease?
Is it possible to identify people who require vaccination with a help of tuberculin test?
Can this disease be curable by various combinations of the antibiotics: streptomycin, isoniazid?
Can such infectious disease be fatal? In what case?
Exercise 6. What do the following abbreviations stand for? If it’s necessary, use the dictionary.
BCG___________ Dx______________
CT____________ HSV_____________
ID____________ M/F_____________
Pen___________ PT_______________
PX____________ MRI______________
T_____________ TB________________
Vacc____________ XR________________
Exercise 7. Answer the following questions to the texts from the chapter “Infections”
What is abscess? When should a medical intervention be performed? What types of abdominal abscesses are known?
What disease is caused by the bacterium Bacillus anthracis? How can a doctor identify it? What form of anthrax is the most deadly?
What is the etiology of Brucellosis (undulant fever) and its treatment?
Is Cat-scratch fever communicative or noncontagious disease? What is the incubation period of this illness? What preventive measures are existed? Is it curable illness?
What is the infectious illness caused by inhaling spores of the fungus Histoplasma capsulatum? Is the patient terminally ill of such disease? What recommendation can a doctor give to avoid it? Is treatment of such infectious disease easy? Is the condition serious or minor? Does progressive Histoplasmosis resemble tuberculosis development?
Do any symptoms of Coccidioidomycosis produce? What therapy is administered in severe or progressive infection caused by the fungus Coccidioides immitis? Is it fatal? What type of germ is it caused by? What is the choice of treatment?
Who is extremely susceptible to the almost 200 different viruses that cause colds? When does cold occur most frequently? Can infection spread to the larynx that may be caused by laryngitis?
What is the difference between influenza and common cold? Are their symptoms similar? Are these conditions caused by an infection or allergy? What is the course of influenza likely to be? What complication can flue cause? What is the most effective preventive measure against influenza?
How is Herpes simplex transmitted? What types of Herpes simplex do you know? Is treatment for Herpes simplex variable? What drugs are prescribed for the type 1 (HSV1)? What preventive measures for type 2(HSV2) should people follow?
Exercise 8. Choose the version and put it in empty space.
1 Up to 40,6C fever causes weakness and it best to treat with …
metapyrin b) asperin c) antiseptic gargle
2 Normal core body temperature, measured orally, doesn’t exceed…
37,2C b) 40C c)36,6C
3 Vaccine can prevent some…
coughing b) simple disease c) viral disease
4 … are ineffective against viral disease.
antibiotic b) allergic remedies c) antifungal antibiotic
5 About 200 different strains of … can produce colds.
virus b) parasite c) Asia influenza
6 The treatment of a cold involves rest, adequate fluid intake and … remedies for the symptom.
Echinacea b) over-the-counter drug c) antimycotic
7 … is frequently taken as a cold preventive.
vitamine C b) vitamine B c) vitamins C and D
8 Influenza is acute viral … of the upper or lower respiratory tract.
complication b) infection c) virus
9 Chills, fatigue and muscles aches are the symptoms of … which begin abruptly.
common cold b) gripp c) pneumonia
10 Viruses are much smaller than …
microorganisms b) parasites c) bacteria
11 Disinfectants are used to destroy … on surfaces.
Microorganisms b) organisms c) microbes
12 Antibiotics and other … are given in shots or orally for infections.
a)antimicrobial agents b) microbial agents c) bacterial agents
13 Antimicrobial agents and antibiotics may be applied locally for superficial …
viruses b) infections c) disease
14 Many antiseptics destroy specific types or forms of microorganisms but not …
bacteria b) gametes c) spores
15 Treatment with drugs is usually effective against most…
nausea b) noninfections c) infections
16 Cat-scratch-disease is carried by cats, especially kittens and this a result of …
viral infection b) bacterial infection c) infection
17 A bearable pain but persistent is labeled … by patient.
an ache b) a pain c) a hurt
18 A headache is associated with colds, flu, sinus infections and …
a) tooth trauma b) nervous breakdown c) meningitis
19 If tonsillitis due to to streptococcal infection is not treated by… it may lead to rheumatic fever or nephritis.
atropine b) antibiotics c) analgesic
20 The effective agent may be transmitted by a patient or carrier in airbone droplets expelled during coughing and sneezing or by direct contact or …
sexual intercourse b) lost of blood c) vaccine
Exercise 9. Fill in the missing words in the text “ History of viral diseases”. Choose from the following.
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Historic descriptions of ______ date back as far as the 10th century BC. The concept of the ______ , however, was not established until the last decade of the 19th century, when several _____ obtained evident that agents far smaller than ______ were capable of causing _____.
The existence of viruses was finally proved when bacteriophages were discovered by independent researches in 1915 and 1917. The question of whether viruses are actually ______ (similar to very tiny bacteria) was resolved in 1935, when the virus responsible for causing _____ in tobacco was isolated and crystallized; the fact that it could be crystallized proved that the virus was not ____ .
Exercise 10. Speak on the following
1 Infections and their types.
2 Bacterial diseases. Its symptoms and treatment.
3 Viral diseases. Its diagnosis and preventive measures.
4 Tuberculosis. Complications and treatment.
5 Fungal diseases. Its etiology and consequences.
6 Abscesses.