Viruses (singular: virus) are tiny, infectious particles and also parasites, i.e. living beings that cannot multiply independently without a host organism. On average, a virus particle is between 20 and 400 nm in size, many times smaller than human cells, bacteria or fungi.
Viruses are not very complex in structure. The most important component of viruses is their genetic material. In the case of viruses, this can either be in the form of DNA (Deoxyribonucleic acid) or RNA (Ribonucleic acid) are available. This feature can also be used to distinguish between DNA and RNA viruses (there are also so-called retroviruses, which are a subgroup of RNA viruses).
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The genetic material can either be in the form of a ring or thread inside viruses. If the virus has not yet established itself in a cell, it is called Virion designated. In almost all cases, the genetic material is surrounded by a capsid, which serves to protect the genetic material. This capsid is a structure of many identical subunits (Capsomeres) which consist of proteins. As a result, the capsid is often referred to as the protein shell, together with the DNA or RNA one speaks of Nucleocapsid.
In addition, some viruses are surrounded by another envelope, the virus envelope, which is made up of a lipid bilayer in which proteins and glycoproteins are partially embedded. The glycoproteins protrude from the shell like spikes, which is why they are also known as "spikesSuch viruses are called enveloped. If the virus envelope is missing, it is called an unenveloped virus.
In addition, some viruses have other components, but never a cytoplasm with cell organelles, as in human, animal or plant cells, which would enable them to have their own metabolism. Since both mitochondria and ribosomes are missing, viruses are not capable of protein biosynthesis on their own and cannot produce their own energy. It has to nestle in a so-called host cell, i.e. a cell of a person, for example, that has the necessary material. There the virus is able to manipulate the cell metabolism in such a way that it adapts to the needs of the virus and, instead of its own proteins, produces proteins that the viruses need to survive.
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Viruses (singular virus)
You can find an overview of all Dr-Gumpert images at: medical illustrations
In addition, it is possible for the virus to multiply by introducing its DNA or RNA into the host cell (replicate). The first step is always for the virus to attach itself to the host cell. The genetic material is then introduced into the cell. There the cover (s) are then removed (uncoating), after which the nucleic acid can enter the cell nucleus. There it practically takes over the control and first of all ensures that the genetic material is reproduced and proteins are produced.
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From these individual components, new virus particles can finally form again. There are two different ways in which the virus can complete replication.
$config[ads_text2] not found1. Lytic cycle: here the cell membrane is completely dissolved, i.e. the cell is destroyed and the new viruses are released.
2. Lysogenic cycle: the cell does not die, but the viruses are only channeled out of it (budding) by taking part of the host cell's cell membrane with them in order to form a shell.
How many viruses emerge from a single host cell during such a process varies from virus to virus. While a cell infected with the herpes virus produces on average only 50 to 100 new viruses, for example, a cell infected with the poliovirus releases more than 1000 new viruses.
Almost all viruses are host-specific, which means that a particular virus usually only affects one particular host organism. Depending on which organism it is, a distinction is made
There are an incredible number of these human viruses, which is why only the most important ones can be mentioned here. Most viruses lead to a specific disease in humans.
The most important human pathogens belong to the DNA viruses:
1. The herpes viruses, in which one again distinguishes a large number of subgroups. The herpes viruses include the human herpes virus 1 and 2, which are responsible for the well-known herpes, which is noticeable in the form of blisters, pain and / or itching and is usually found on the lips (Herpes labialis, especially HHV 1) or in the genital area (Genital herpes, especially HHV 2) manifested.
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The HHV 6 is responsible for the so-called 3-day fever.
HHV 8 is a rarer herpes virus, as it only really leads to an infection in people with a weak immune system (for example people infected with HIV), which causes a certain type of cancer, Kaposi's sarcoma.
2. The group of smallpox viruses includes, on the one hand, the triggers of harmless warts and, on the other hand, those viruses that cause dangerous smallpox.
3. The hepatitis B virus causes liver inflammation.
4. Of human papillomaviruses (HPV) There are various different types that also lead to different clinical pictures. While most (e.g. types 6 and 11) are relatively harmless, some (e.g. types 16 and 18) can develop cancer of the cervix (Cervical cancer) cause.
5. Adenoviruses are often the cause of diarrhea or colds with a runny nose.
Of particular importance in the case of RNA viruses for humans are:
Viruses can not only cause disease, however. Much research is currently being carried out into using viruses as a therapy. For example, certain viruses should be able to be used against certain forms of cancer or serve as vaccines.
$config[ads_text1] not foundYou may also be interested in this topic: Viral infection
It is more difficult to cure an infection caused by viruses than, for example, bacteria-related diseases, because viruses are not cells of their own but are always found in human cells. That is why killing a virus also means killing a body cell.
In order to fight viruses, so-called antivirals are used. These are drugs that prevent viruses from multiplying or at least limit them.
The main targets of antiviral drugs are:
However, these agents are often associated with sometimes serious side effects.
Read more about here Antiviral drugs.
The human papilloma virus - HPV for short - is the main cause of the known skin warts and can increase the risk of certain types of tumors developing. In the group of HP viruses, over 150 different types can now be found, which, roughly speaking, differ in the severity of the warts they cause.
Please also read the article: Human papilloma virus
On the one hand, there are types that cause normal skin warts that form on the hands, feet or, for example, the armpits. Although they are not very aesthetic, they are harmless and usually disappear on their own.
Second, there are types that cause harmless genital warts called condylomas. This is where transmission usually occurs during sexual intercourse. These warts are also unaesthetic, but not tumorous skin changes.
Third, there are types that cause skin changes in the genital area, which have a cancer tendency.
A well-known example of this is cervical cancer, which also explains why you can “vaccinate” yourself against a type of cancer.
Viruses are very easy to transmit because they can easily survive for several days in the environment without dying. The virus then penetrates through microscopic skin lesions and attacks human skin cells, whereupon the warts develop.
Read more about this: Vaccination against cervical cancer, symptoms of cervical cancer
The Ebola virus is one of the so far little researched and dangerous viruses whose infection is associated with a high death rate.
Please also read the article: What is the Ebola Virus?
The virus probably originated in a species of flying fox that is native to a cave in West Africa. It was from here that it was transmitted to the person who spread the virus.
The subsequent illness begins with unspecific symptoms such as conjunctivitis and only develops a characteristic rise and fall in body temperature after about a week. The result is rash-like reddening of the skin and ultimately an infection of the body's own immune cells and massive blood loss as the body's own blood vessels lose their tightness.
At present, only the symptoms can be treated; systematic therapy to combat the virus in the form of drugs or vaccinations are not yet available.
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The respiratory syncytical virus (RSV for short) is a cause of respiratory diseases, especially in childhood. The virus usually leads to epidemic-like outbreaks worldwide in late autumn. It mainly affects the upper respiratory tract, but in particularly severe cases it can also reach the lungs and lead to lung or pleural inflammation. In the vast majority of cases, however, only the throat and bronchi are affected. Sometimes, however, it also leads to an otitis media.
The viruses cause minor cell death of the tracheal cells and in the worst case can clog them with degradation products or the resulting mucus, which leads to shortness of breath.
The aforementioned respiratory diseases mainly occur in young children up to the age of three. After this point in time, almost 100% of the antibodies against the virus have formed, so that the infections only appear as a mild cough or a slight throat irritation.
Treatment is currently still symptomatic. One tries to loosen the mucus in the bronchi and to cure any inflammation that may arise.
The elimination of the virus, however, is left to the body's own defenses. In very rare cases and if the disease progresses badly, a so-called antiviral agent can be used.
You can find everything on this topic in our article: The RS virus
The human immunodeficiency virus, or HIV for short, actually consists of two types: HIV 1 and HIV 2.
These can in turn be divided into different subspecies depending on the location of the outbreak. In all likelihood, HIV is derived from a similar type of virus. This affects chimpanzees and is called SIV, Simian Immunodeficiency Virus. The transmission and conversion of the virus probably took place around 1900 in West Africa and spread from here to the world.
There are currently around 37 million sick people worldwide and around 1 million fatalities every year.
The transmission of the HI virus can occur either through blood, through sexual intercourse or from the mother to the unborn child. The likelihood of being infected depends on the amount of virus transmitted.
After the transmission, the first thing you notice is cold symptoms. The full expression of the virus infection, the so-called AIDS disease, only occurs after a few months or years. There are permanent symptoms of infection, the likelihood of developing a tumor is drastically increased and structures of the nervous system are also attacked.
Fortunately, the viral load can be well contained and the manifestation of the disease reduced if patients see a doctor immediately after exposure to HIV-infected body materials.
The difficulty in treating HIV or the reason why there is no effective vaccination against HIV is that the virus is extremely changeable and is changed within a reproduction cycle in such a way that it is no longer recognized by the human immune system.
Please also read: Symptoms of HIV, Symptoms of AIDS
Rotaviruses cause diarrhea. It is estimated that up to 150 million people are infected with rotavirus every year. Many of the infections are barely noticeable because you will come into contact with rotaviruses over the course of your life and thus maintain an almost permanent immune protection.
The disease is usually only dangerous for small children, older patients and in countries where there is not enough clean water.
The viruses attack the small intestine and, through cell death, reduce the ability to absorb water, which is why patients should drink even more water to counteract this lack of fluids.
The diarrhea is usually not bloody and is often associated with vomiting. Fever develops better than ever, only elevated temperatures of up to approx. 38 degrees Celsius.
Read more about this: Home remedies to treat diarrhea, anti-vomiting medication
The viruses are usually transmitted through improperly cleaned hands after using the toilet. The next person affected then spreads the viruses, for example through food, into their mouth, from where they find their way into the small intestine, where they can lodge and cause diarrhea.
The illness usually lasts a maximum of one week.
There is no vaccination, the affected person is given more fluids and their salt balance is checked.
Read more about this: Vaccination against the rotavirus
In addition to the rotavirus, the norovirus is the main cause of viral vomiting and diarrhea diseases: the virus lodges in the early small intestine and causes the intestinal cells there to decline.
As a result, the intestine can no longer absorb enough water from the stool and severe diarrhea occurs as a result. However, the disease is mainly characterized by severe vomiting and severe abdominal cramps.
The symptoms only last two to three days and then go away on their own. The disease mainly affects children shortly before school age.
The severe loss of fluid can make it dangerous for people who do not consume enough water to make up for the loss. In the concrete case, it is toddlers and old people who can “dry out” in the worst case.
The disease is treated purely symptomatically: people are given more fluids and attempts are made to maintain the patient's salt balance.
Read more about this: Gastrointestinal virus - causes and treatment, homeopathy for vomiting
Basically one cannot speak of "the" hepatitis virus. At least five hepatitis viruses are currently known to research. From hepatitis A to hepatitis E, the viruses differ both in their clinical pictures and in their danger to humans. Even if there are several hundred thousand people with hepatitis in Germany, this virus is more of a problem in developing and emerging countries.
In Germany, those affected can now be helped very well - provided they are undergoing medical treatment, so that the probability of dying from a hepatitis infection is very low.
Read more on this topic: Vaccination against hepatitis B, symptoms of hepatitis A
