Introduction
Viruses are a very common type of infectious disease. Many of the most common human diseases are viral. There are literally hundreds of types of viral conditions.
Viruses are the smallest life-form existing, since they are not even a single cell. It is almost like they are not alive at all. They are small strands of DNA-like cell material. A virus consists mostly of RNA and cannot survive without host cells.
Causes
Viruses are infectious microbes that can be inside or outside cells. They are little strips of DNA (or RNA) usually wrapped inside a tiny capsule. Viruses are not even a single cell, but are a tiny part of a cell, and thus they are much smaller even than bacteria. Viruses are not alive in the normal sense. They do not feed, nor do they generate energy or waste products. Viruses are effectively inert until they attach to a live body cell. But once they attach, they become alive in a sense. They enter the cell, breaking open the capsule, so that their inside contents of DNA or RNA strips enter the cell. Because this viral DNA looks like normal DNA, the cell starts to copy it like the cell does to ordinary DNA. In this way, the body cell is tricked into making many copies of the virus inside the cell. Eventually, the cell is killed and these newly created viruses are expelled into the body to infect more cells.
Unlike most bacteria, most viruses do cause disease because they invade living, normal cells, such as those in the human body. They then multiply and produce other viruses like themselves. Each virus is very particular about which cell it attacks. Various human viruses specifically attack particular cells in the body's organs, systems, or tissues, such as the liver, respiratory system, or blood cells.
News
Bird Flu Virus Can Survive Two Years in Landfill
Carcasses of infected bi
Reds continue to be infectious, study finds
FRIDAY, June 5 (Health Day News) — Poultry carcasses infected with the bird flu virus can remain infectious in municipal landfills for as long as two years, say Nebraska researchers.
Hundreds of millions of chickens and ducks infected with bird flu have died or been killed worldwide in an effort to control the spread of the disease, they noted. The remains are disposed of in different ways, including burial in landfills. For example, the carcasses of more than 4 million poultry that were culled or died during a 2002 outbreak in Virginia were placed in municipal landfills, according to a news release from the American Chemical Society.
But the safety of landfill disposal has received little attention, said the researchers who conducted the study. They found that the bird flu virus can survive in landfill leach ate — liquid that drains from a landfill — for at least 30 days and up to two years.
Factors that most reduced the virus' survival times were elevated temperatures and acidic or alkaline pH, the news release noted.
"Data obtained from this study indicate that land filling is an appropriate method of disposal of carcasses infected with avian influenza," concluded Shannon L. Bartle-Hunt and colleagues, who noted that landfills are designed to hold material for much longer than two years
What Causes A Sore Throat?
Sore throat is a symptom of many medical disorders. Infections cause the majority of sore throats and are contagious. Infections are caused either by viruses such as the flu, the common cold, mononucleosis, or by bacteria such as strep, my co plasma, or homophiles. While bacteria respond to antibiotic treatment, viruses do not.
Viruses: Most viral sore throats accompany flu or colds along with a stuffy, runny nose, sneezing, and generalized aches and pains. These viruses are highly contagious and spread quickly, especially in winter. The body builds antibodies that destroy the virus, a process that takes about a week. Sore throats accompany other viral infections such as measles, chicken pox, whooping cough, and croup. Canker sores and fever blisters in the throat also can be very painful. One viral infection takes much longer than a week to be cured: infectious mononucleosis, or "mono." This virus lodges in the lymph system, causing massive enlargement of the tonsils, with white patches on their surface and swollen glands in the neck, armpits, and groin. It creates a severely sore throat and, sometimes, serious breathing difficulties. It can affect the liver, leading to jaundice— yellow skin and eyes. It also causes extreme fatigue that can last six weeks or more. "Mono," a severe illness in teenagers but less severe in children, can he transmitted by saliva. So it has been nicknamed the "kissing disease," but it can also be transmitted from mouth-to-hand to hand-to-mouth or by sharing of towels and eating utensils.
Bacteria: Strep throat is an infection caused by a particular strain of streptococcus bacteria. This infection can also damage the heart valves (rheumatic fever) and kidneys (nephritis), cause scarlet fever, tonsillitis, pneumonia, sinusitis, and ear infections. Because of these possible complications, a strep throat should be treated with an antibiotic. Strep is not always easy to detect by examination, and a throat culture may be needed. These tests, when positive, persuade the physician to prescribe antibiotics. However, strep tests might not detect other bacteria that also can cause severe sore throats that deserve antibiotic treatment. For example, severe and chronic cases of tonsillitis or tensile abscess may be culture negative. Similarly, negative cultures are seen with diphtheria, and infections from oral sexual contacts will escape detection by strep culture tests. Tonsillitis is an infection of the lumpy tissues on each side of the back of the throat. In the first two to three years of childhood, these tissues "catch" infections, sampling the child's environment to help develop his immunities (antibodies). Healthy tonsils do not remain infected. Frequent sore throats from tonsillitis suggest the infection is not fully eliminated between episodes. A medical study has shown that children who suffer from frequent episodes of tonsillitis (such as three- to four- times each year for several years) were healthier after their tonsils were surgically removed. Infections in the nose and sinuses also can cause sore throats, because mucus from the nose drains down into the throat and carries the infection with it. The most dangerous throat infection is epiglottises, caused by bacteria that infect a portion of the larynx (voice box) and cause swelling that closes the airway. This infection is an emergency condition that requires prompt medical attention. Suspect it when swallowing is extremely painful (causing drooling), when speech is muffled, and when breathing becomes difficult. A strep test may miss this infection.
Allergy: The same pollens and melds that irritate the nose when they are inhaled also may irritate the throat. Cat and dog dander’s and house dust are common causes of sore throats for people with allergies to them.
Irritation: During the cold winter months, dry heat may create a recurring, mild sore throat with a parched feeling, especially in the mornings. This often responds to humidification of bedroom air and increased liquid intake. Patients with a chronic stuffy nose, causing mouth breathing, also suffer with a dry throat. They need examination and treatment of the nose. Pollutants and chemicals in the air can irritate the nose and throat, but the most common air pollutant is tobacco smoke. Other irritants include smokeless tobacco, alcoholic beverages, and spicy foods. A person who strains his or her voice (yelling at a sports event, for example) gets a sore throat not only from muscle strain but also from the rough treatment of his or her throat membranes.
Reflux: An occasional cause of morning sore throat is regurgitation of stomach acids up into the back of the throat. To avoid reflux, tilt your bed frame so that the head is elevated four- to six-inches higher than the foot of the bed. You might find antacids helpful. You should also avoid eating within three hours of bedtime, and eliminate caffeine and alcohol. If these tips fail, see your doctor.
Tumours: Tumours of the throat, tongue, and larynx (voice box) are usually (but not always) associated with long-time use of tobacco and alcohol. Sore throat and difficulty swallowing, sometimes with pain radiating to the ear, may be symptoms of such a tumour. More often the sore throat is so mild or so chronic that it is hardly noticed. Other important symptoms include hoarseness, a lump in the neck, unexplained weight loss, and/or spitting up blood in the saliva or phlegm.
