Their crown-like appearance under the microscope gave them the name: Coronaviruses have long been regarded as the harmless cause of colds. But the pathogen from Wuhan is the third example that they can do it differently. Here we answer a few of the most important questions about this virus family and its latest offspring.
What are viruses?
Viruses are tiny structures that contain genetic material (DNA or RNA) but are not considered to be independent living beings, They can only multiply in other cells and use their metabolism for this. host organisms can be bacteria, but also archaebacteria, fungi and other nucleated unicellular and multicellular organisms – from slipper animals and plants to humans. Viruses were discovered at the end of the 19th century. The first was one that infested tobacco plants: the tobacco mosaic virus, which is still very important in research today.
Why do viruses trigger diseases?
This almost banal-sounding question is not easy, and certainly not comprehensive, to answer. Infection with a virus can be unproblematic for the infected organism, but it can also be threatening. This is how people catch a lot of different viruses in the course of their lives.
Even if the immune system does not immediately neutralize them, many have little or no effect. Other that rabies virus about, are fatal in almost 100 percent of cases, These differences in “virulence”, which in some definitions include not only the disease-causing potential but also the ability to be transferred to other organisms, are anything but completely understood.
One hypothesis why some viruses make you very sick is that this in the interest of the virus is because it facilitates its spread – for example, through coughing or excretion through skin ulcers or diarrhea. This contradicts that very similar viruses behave very differently here.
[Inour[Inunserem Super FAQ on the Coronavirus epidemic we answer the 40 most important questions.]
So there is Gastrointestinal virusesthat cause massive diarrhea and vomiting and others that do not cause any symptoms, but can obviously spread just as well or better. It seems clear that proteins that help the virus evade the host’s immune system contribute to virulence.
So that a virus can spread, it has to destroy its host cell, and many destroyed cells mean inflammation and usually also increased “poison” concentrations, triggered among other things by the dying tissue, which leads to symptoms of illness.
In fact, a so-called seems evolutionary strategy of viruses to be able to find a balance between damage to the organism and sparing it, because an immediately dying host is not a good vehicle for spreading.
Too little cell destruction and thus the release of viruses is an equally limiting factor. This could also be a reason why new viruses that have jumped from animals to humans can be very dangerous, since such a balance only has to be developed over long evolutionary periods.
What are corona viruses?
Corona viruses are comparative large round viruses that have an envelope, The name derives from the Latin Word for crown because the viruses look crown-like under the electron microscope. Researchers have described hundreds of types of corona viruses. They can cause very different types of diseases in mammals, birds and fish.
As they multiply, their genetic makeup changes every time. This can cause them to move from one species to another – and suddenly become dangerous for people, even though they have only infected animals so far. Corona viruses, which can be dangerous to humans, carry the Abbreviation HCoV (human pathogenic coronaviruses).
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Four of these HCoV occur worldwide. Scientists estimate that they responsible for about ten to thirty percent of all upper respiratory infections could be. Researchers have found the greatest variety of coronaviruses in bats. Therefore, they assume that the animals are a reservoir for many corona viruses. Pets and farm animals can act as intermediate hosts, in which the viruses continue to multiply and thereby change their genetic makeup.
What are the best known corona viruses and where do they come from?
For a long time, doctors and virologists believed that coronaviruses only cause normal colds in humans. That changed with two particularly pathogenic virus variants that triggered epidemics: the SARS coronavirus (Severe acute respiratory syndrome) and the Mers coronavirus (Middle east respiratory syndrome).
Around 2,500 people have been infected with Mers, which occurs primarily on the Arabian Peninsula, since 2012, about one in three died, Both viruses have their origin in animals. The most likely reservoir of the Sars pathogen are bats or larval rollers, a sneak cat species that is considered a delicacy in China. The Mers coronavirus originates from bats and is transmitted from dromedaries to humans.
How Infectious Are Sars & Co.?
Since precise data on the Wuhan virus is so far lacking, So far, experts have mostly referred to Sars in their assessment, Here patients seem to have been particularly infectious relatively late in the course of the disease. This also explains why a large number of doctors and nurses became infected, because these patients were mostly accommodated in hospitals.
In addition, according to Anthony Fauci from the National Institute of Allergy and Infectious Diseases in Bethesda in the United States and two of his colleagues in a recent article in the Journal of the American Medical Association, the virus could be infected in more than a quarter of patients due to the disease necessary interventions – such as mechanical ventilation – have found good conditions for dissemination.
Because this creates aerosols Clouds of droplets in the airthat can be inhaled easily. In fact, most of the documented cases of human-to-person contagion at Sars were among hospital staff.
That Sars – unlike normal corona cold viruses – severe symptoms in the lungs According to the researchers, this may be due to the “basic virology”: those molecules on cell surfaces that the virus needs for docking occur primarily in deeper regions of the respiratory tract in humans. Fauci also writes that many aspects of the transmission of the Sars virus are still not understood today.
How was the new corona virus discovered?
The new corona virus, which first appeared in central China’s Wuhan in late December 2019, has the provisional name 2019-nCoV, Just a few days after the first official reports, scientists from Shanghai succeeded in decoding the genetic makeup of the virus.
Developed on this basis a team around the virologist Christian Drosten from the Charité the first diagnostic test ever to be used to identify infections. According to initial analyzes, the new virus appears to have structural similarities to the Sars virus and could also use similar binding sites in the body for docking.
Where does the corona virus come from and how can it be transmitted?
The virus was originally transmitted from an animal to humans. The outbreak probably started at a market in Wuhanwhere fish and seafood, but also snakes, pheasants and other animals were sold.
Unsanitary contact with infected animals may have triggered almost all of the initial cases. Meanwhile, however, it is considered certain that the virus also transmitted from person to person can be. On Thursday, the World Health Organization announced that it was at least four generations of the virus have to give.
That means that it probably jumped from an infected animal to a person, who then infected another person who passed the pathogen on again. This is likely to happen both from droplet and smear infection, The former means that the virus is absorbed through inhaled aerosols, such as those that occur when you sneeze.
A smear infection can occur when someone especially surfaces or people contaminated with hands and then touched your own mucous membranes, especially your mouth, nose and eyes. On Thursday, the WHO announced the first estimate of the “basic reproduction number” of the virus: According to this, an infected person infects about 1.4 to 2.5 other people with the virus on average.
To stop an outbreak, it must be brought under one. Michael Osterholm, director of the Center for Infectious Disease Research and Policy in Minnesota, told the US online magazine Stat: “It gives me little hope that everything that is happening now will soon control the outbreak.”
How threatening is the corona virus for infected people?
Nothing precise can still be said about this. As of Friday, January 31st, approximately 10,000 cases were known 213 people have died as a result of the infection,
According to the authorities, the first reported deaths mainly affected older people with some serious previous illnesses.
However, on Friday, January 24, a Chinese research team released clinical data (here as a PDF) on the first 41 patients in the outbreak who disagree with this initial assessment. Therefore only one in three had an accompanying disease, such as diabetes, high blood pressure or cardiovascular diseases. The median age of onset was 49 years.
Many experts did first suspected that the new corona virus is less deadly than Sars and Mers, However, in order to be able to analyze this precisely, further evaluations of the cases of infection are necessary. You have to know not only how many people die, but also how many have recovered – and ideally also how many survive the infection without becoming noticeably ill.
What treatments would be possible?
Currently, unlike against herpes viruses or HIV, no specifically effective drugs against coronaviruses approved, Treatment is symptomatic, such as intravenous fluids, cortisone medication for inflammation and swelling, and, if necessary, ventilation. In addition, people are treated with a combination of two antivarals known from HIV therapy, a study is ongoing. In addition, studies are currently ongoing with antiviral drugs that have worked against Mers coronaviruses in animal experiments.
Scientists are also examining whether vaccine candidatesthat were developed against Mers and Sars could also help against 2019-nCoV. Results are expected in the coming weeks, when safety and clinical tests could start. As long as consistent hygiene remains the best precaution against the new virus.
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