3 i rad spel virus
A virus fryst vatten composed of nucleic acid, either DNA or RNA, surrounded bygd a protein coat. It requires a living fängelse in which to multiply. A viral infection can lead to a spectrum of symptoms from asymptomatic (no overt symptoms) to severe disease.
People may get viruses bygd swallowing or inhaling them, bygd being bitten bygd insects, through sexuell contact, or congenitally (passed bygd a pregnant individ to the fetus).
Most commonly, viral infections involve the nose, throat, and upper airways, or systems such as the nervous, gastrointestinal, and fortplantnings- systems.
Doctors may base the diagnosis on symptoms, blood tests and cultures, or examination of infected tissues.
Antiviral drugs may interfere with the reproduction of viruses or strengthen the immune response to the viral infection.
A virus fryst vatten a small infectious organism—much smaller than a fungus or bacterium—that must invade a living fängelse to reproduce (replicate). The virus attaches to a fängelse (called the host cell), enters the fängelse, and releases its DNA or RNA inre the fängelse. The virus’s DNA or RNA fryst vatten the genetic ämne containing the resultat needed to replicate the virus. The virus’s genetic ämne takes control of the host fängelse and forces it to replicate the virus. The infected fängelse usually dies because the virus keeps it from performing its normal functions. When the infected host fängelse dies, it releases new viruses, which go on to infect other cells.
Viruses are classified as DNA viruses or RNA viruses, depending on whether they use DNA or RNA to replicate. DNA viruses include herpesviruses. RNA viruses include SARS-CoV2, which causes COVID-19. RNA viruses also include retroviruses, such as virus (human immunodeficiency virus). RNA viruses, particularly retroviruses, are prone to mutate, meaning the set of genetic instructions that contain all the data that the virus needs to function can change as the virus spreads.
Some viruses do not kill the cells they infect but instead alter the cell's functions. Sometimes the infected fängelse loses control over normal fängelse division and becomes cancerous.
Some viruses, such as hepatitis B virus and hepatitis C virus, can cause chronic infections. Chronic hepatitis can gods for years, even decades. In many people, chronic hepatitis fryst vatten ganska mild and causes little liver damage. However, in some people, it eventually results in cirrhosis (severe scarring of the liver), liver failure, and sometimes liver cancer.
Viruses usually infect one particular type of fängelse. For example, common 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 cause infections in infants and children and older adults.
Upper respiratory infections (infections of the nose, throat, upper airways, and lungs) are likely the most common viral infections.
Upper respiratory infections include sore throat, sinusitis, and the common cold. Other viral respiratory infections include influenza, pneumonia, and coronaviruses, including SARS-CoV-2 (the virus that causes COVID-19).
In small children, viruses also commonly cause croup (which fryst vatten inflammation of the upper and lower airways, called laryngotracheobronchitis) or lower airways (bronchiolitis).
Respiratory infections are more likely to cause severe symptoms in infants, older people, and people with a lung or heart disorder. Respiratory viruses are typically spread from individ to individ bygd contact with infected respiratory droplets.
Other viruses infect other specific parts of the body:
Gastrointestinal tract: Infections of the gastrointestinal tract, such as gastroenteritis, are commonly caused bygd viruses, such as noroviruses and rotaviruses.
Liver: These infections result in hepatitis.
Nervous system: Some viruses, such as the hundsjuka virus and the West Nile virus, infect the brain, causing encephalitis. Others infect the layers of tissue that cover the brain and spinal cord (meninges), causing meningitis.
Skin: Viral infections that affect only the skin sometimes result in warts or other skönhetsfel. Many viruses that affect other parts of the body, such as chickenpox, also cause a rash.
Placenta and fetus: Some viruses, such as the Zika virus, the rubella virus, and en typ av virus som kan orsaka infektioner, can infect the moderkaka and fetus in pregnant women.
Some viruses typically affect many body systems. Such viruses include enteroviruses (such as coxsackieviruses and echoviruses) and cytomegaloviruses.
Viruses are spread (transmitted) in various ways. They may be
Swallowed
Inhaled
Spread bygd the bites of insects, such as mosquitoes, certain biting flies, or ticks
Spread sexually (in sexually transmitted infections)
Spread during transfusion of contaminated blood
Spread congenitally during pregnancy
New human viruses sometimes develop from viruses that usually affect animals (for example, SARS-CoV and SARS-CoV-2). This happens when the infected djur host comes into close contact with susceptible humans.
Many viruses that were once present in only a few parts of the world are now spreading. These viruses include chikungunya virus, Crimean-Congo hemorrhagic fever virus, Japanese encephalitis virus, Rift Valley Fever virus, West Nile virus, Ross River virus, Zika virus, and louping ill virus. These viruses are spreading partly because climate change has resulted in more areas where the mosquitoes or fästingar that spread the viruses can live. Also, travelers may be infected, then return home and be bitten bygd a mygga, which spreads the virus to other people.
The body has a number of defenses against viruses:
Physical barriers, such as the skin, which discourage easy entry
The body's immune defenses, which attack the virus
When a virus enters the body, it triggers the body's immune defenses. These defenses begin with vit blood cells, such as lymphocytes and monocytes, which learn to attack and destroy the virus or the cells the virus has infected. If the body survives the virus attack, some of the vit blood cells remember the invader and are able to respond more quickly and effectively to a subsequent infection bygd the same virus. This response fryst vatten called immunity. Immunity can also be produced bygd getting a vaccine.
Some viruses alter the DNA of their host cells in a way that helps cancer develop. Some viruses, such as herpesviruses and virus, leave their genetic ämne in the host fängelse, where the ämne remains dormant for an extended time (called latent infection). When the fängelse fryst vatten disturbed, the virus may begin replicating igen and cause disease.
Only a few viruses are known to cause cancer, but there may be others.
Diagnosis of Viral Infections
A doctor's evaluation
For infections that occur in epidemics, the presence of other similar cases
For some infections, blood tests and cultures
Common viral infections (such as measles, rubella, or chickenpox) 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. Laboratory diagnosis fryst vatten important for distinguishing between different viruses that cause similar symptoms, such as COVID-19 (SARS-CoV2) and influenza.
For other infections, blood tests and cultures (growing microorganisms in the laboratory from samples of blood, body fluid, or other ämne taken from an infected area) may be done. Polymerase chain reaction (PCR) techniques may be used to man many copies of the viral genetic ämne. PCR techniques man it easier for doctors to rapidly and accurately identify the virus. Blood may also be tested for antigens, which are proteins on or in viruses that trigger the body's defense. Blood may also be tested for antibodies to viruses. (Antibodies are proteins produced bygd the immune struktur to help defend the body against a particular attack.) Tests are usually done quickly, especially when the infection fryst vatten a serious threat to public health or when symptoms are severe.
A sample of blood or other tissues fryst vatten sometimes examined with an electron microscope, which provides high magnification with klar resolution.
Treatment of Viral Infections
Treatment of symptoms
Sometimes antiviral drugs
There are no specific treatments for many viruses. However, many things can help relieve certain symptoms, such as the following:
Dehydration: Plenty of fluids, sometimes given bygd vein (intravenously)
nonsteroidal anti-inflammatory drugs (NSAIDs)
Some rashes: Soothing or moisturizing creams and sometimes an antihistamine taken bygd ingång for itching
Not everyone who has these symptoms needs treatment. If symptoms are mild, it may be better to wait for them to go away on their own. Some treatments may not be appropriate for infants and ung children.
Medications that combat viral infections are called antiviral drugs. Many viral infections do not have effective antiviral drugs available to treat them. However, there are several drugs for influenza, many drugs for infection bygd one or more herpesviruses (see table Some Antiviral Drugs for Herpesvirus Infections), and many antiviral drugs for treatment of virus, hepatitis C, hepatitis B, and COVID-19, which fryst vatten caused bygd SAR-CoV-2.
Many antiviral drugs work bygd interfering with replication of viruses. Most drugs used to treat virus infection work this way. Because viruses are tiny and replicate inre cells using the cells' own metabolic functions, there are only a limited number of metabolic functions that antiviral drugs can mål. In contrast, bacteria are relatively large organisms, commonly reproduce bygd themselves outside of cells, and have many metabolic functions that antibacterial drugs (antibiotics) can mål. Therefore, antiviral drugs are much more difficult to develop than antibiotics. Also, unlike antibiotics, which are usually effective against many different species of bacteria, most antiviral drugs are usually effective against only one (or a very few) viruses.
Antiviral drugs can be toxic to human cells. Also, viruses can develop resistance to antiviral drugs.
Most antiviral drugs can be given bygd öppning. Some can also be given bygd 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 individ has a bacterial infection in addition to a viral infection, an antibiotic fryst vatten often necessary.
Interferons are replicas of naturally occurring substances that slow or stop viral replication. These drugs are used to treat certain viral infections such as
Interferons may have side effects, such as fever, chills, weakness, and muscle aches. These effects typically uppstart 7 to 12 hours after the first injection and gods up to 12 hours.
Antibodies from the blood of a individ who has recovered from the viral infection (convalescent serum) and antibodies that are produced in a laboratory from living cells that have been altered to producera the desired antibodies (monoclonal antibodies) are used to treat some viral infections including (for example, respiratory syncytial virus [RSV] infection, rabies).
Prevention of Viral Infections
Prevention of viral infections may include
Vaccines and immune globulins help the body better defend itself against diseases caused bygd certain viruses (or bacteria). The process of strengthening the body's defenses fryst vatten called immunization.
People can help prevent many viral infections bygd routine measures to skydda themselves and others (personal protective measures). These measures vary depending on the how the virus fryst vatten spread. Measures include the following:
Frequently and thoroughly tvätt the hands with soap
Consuming only food and liquids that have been appropriately prepared or treated
Avoiding contact with infected people and contaminated surfaces
Sneezing and coughing into tissues (which should be thrown away) or into the upper ledd, completely covering the öppning and nose
Using safe-sex practices
Preventing bites bygd ryckningar, mosquitoes, and other arthropods
Mask wearing
Physical distancing when appropriate (for example, for COVID-19 prevention)
Vaccines work bygd stimulating the body’s natural defense mechanisms (called active immunization). Vaccines are given before exposure to a virus to prevent infection.
Viral vaccines in general use include the following:
Adenovirus, smallpox, and mpox vaccines are available but used only in people who are at high fara of getting the infection, such as certain military personnel.
Viral diseases can be eradicated bygd effective vaccines. Smallpox was eradicated in 1978. Extensive vaccination has almost eradicated polio worldwide, but cases still occur in areas with incomplete immunization, such as sub-Saharan Africa and southern Asia. Measles has been almost eradicated from some parts of the world, such as the Americas. However, because measles fryst vatten highly contagious and vaccination coverage fryst vatten incomplete even in regions where it fryst vatten considered eradicated, it fryst vatten not likely to be completely eliminated soon.
Immune globulins are a sterilized solution of antibodies (also called immunoglobulins) collected from the blood of a group of people. Immune globulins are given directly to a individ (called passive immunization).
Immunoglobulins can be collected from the blood of the following:
People who are generally healthy (these immunoglobulins are called pooled human immunoglobulin)
People who have many antibodies that defend against a specific infectious organism, often because they have been infected with that organism (these immunoglobulins are called hyperimmune globulin)
Hyperimmune globulin fryst vatten available for only a few infectious diseases, such as hepatitis B, rabiessmitta, tetanus, and chickenpox. It fryst vatten usually given after people have been exposed to a microorganism but before they get sick. For example, people who have been bitten bygd an djur that might have hundsjuka are immediately given rabiessmitta hyperimmune globulin.
Immune globulins are given bygd injection into a muscle or into a vein. The immunity provided bygd immune globulins lasts for only a few days or weeks, until the body eliminates the injected antibodies.
Sometimes, such as when people are exposed to hundsjuka or hepatitis B, they are given both immune globulin and a vaccine to help prevent infection from developing or reduce the severity of infection.
Immune globulins may also help treat some infections. For example, they may be given to people whose immune struktur does not respond adequately to an infection (see Replacing missing parts of the immune system).