The causative agent of Sars-CoV-2 is currently being explored as well as possible. An important question: Is the spread of the Coronavirus only via direct contact and coughed droplets or through aerosols in the air? What studies show and experts say.
Scientists from South Korea wanted to the question of whether Sars-CoV-2 can also be due to aerosols in the air, on the bottom. For this you have studied in ferrets, whether this can only infect via direct contact or also by a stream of air with the Covid-19-pathogens Sars-CoV-2. Their observations, published recently in the journal "Cell Host & Microbe".
Aerosols are finest moisture mist. Such, we set about on the Exhale free.
Only through direct contact with animals infected so that they showed symptoms
Ferrets are not suitable for such an attempt, however, only of limited use, as you show in your course of the disease, although some Similarities to humans, however. Also ferrets develop, according to the researchers a fever, the Virus multiplies in the upper respiratory tract and can be for days in saliva samples, urine, and feces evidence. Serious illness or even deaths, it was not among the animals.
The researchers built for their investigation of two different Experiments. To a you gave with Sars-CoV-2 infected animal in a cage with healthy ferrets. It took two days until all the animals were infected with the Virus.
On the other, they were infected and healthy animals in two different cages. In the cage of the healthy animals in the surroundings was launched in the air of infected animals. Symptoms developed in this case in healthy ferrets.
The researchers were able to demonstrate up to four days of Virus RNA, i.e. viral DNA in the nasal mucosa and the feces of a healthy ferret, in the case of an animal, you even found antibodies against Sars-CoV-2.
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The ferrets could, therefore, only through direct contact , so infected, that they symptoms showed. A Transmission over the air, according to the researchers, but cannot be ruled out.
Roman Wölfel, a physician and Director of the Institute for Microbiology of the German armed forces in Munich, sees the study in Parts of is critical. While the direct Transferability of the pathogen can be demonstrated, says woelfel: “the animals of the indirect contact model, the data of the here described studies do not convince me, however, of an aerosol transmission.”
Because the animals would show no typical symptoms, the detection of the viruses in the RNA was high. Also, the fact that one of the animals has formed antibodies, did not speak for a Transmission over the air. “If an infection would have actually been transferred, I would increases here are also significant Titers of the neutralizing antibodies expect." The physician concluded that further studies are needed to draw meaningful conclusions.
Various studies are not Aerosol-Transmission
Has driven the discussion over the possible spread of the Coronavirus by aerosols, however, also a letter from the National Academics of Science, Engineering and Medicine in the United States (NAS). Therein, the NAS-infection Loge Harvey Fineberg and his colleagues write that the current research – although it can be very difficult and currently only limited evidence – the possibility of support, "that Sars-CoV-2 could be due to aerosols, the spread, at the expiration of infected people entstehen".
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Fineberg refers in his letter, among other things, on a study by the University of Nebraska, the end of March on the Preprint Server "medRxiv" was published. The researchers in the room where Covid-19-patients were isolated, virus-RNA, even on hard-to-reach surfaces and in air samples collected in more than two meters distance from the patient, had found. “The fact that this RNA is found there, shows that the Virus spreads through aerosols,” said study lead author Joshua Santarpia, therefore. However, no complete virus could be found in the samples.
The authors of the NAS, writing that studies, the PCR assays to the genome of the Virus to identify, may be the Virus is not a lot of evidence that would be sufficient to cause an infection. However, the Emergence of viral genetic material (RNA) in aerosols suggest the possibility for such transmission of the virus.
In mid-March had pointed to a study in the “New England Journal of Medicine” for the first time, then that virus from aerosol droplets in the breathing air could be transported that are smaller than five microns. They could float for up to three hours long through the air, the pathogen infectious to stay.
The study was widely criticized, because the Experiment have to do with the reality little. Charité-virologist Drosten said in the NDR Podcast about: “The Virus is in the air for a short period of time. It will coughs and stands as a coarse to medium-large tröpfiges Aerosol in the air. And the falls relatively quickly to the ground. This is not so, that a Virus is as a cloud in the air for hours, and also in the neighboring room.”
Experts advise to nationwide use of the mouth-nose cover or in a public space
At this time, so clarified from a scientific point of view, finally, whether the pathogen can be transmitted not only by coughing, but also via small droplets when Breathing.
“In Essence, the conclusion of the American authors conclude that aerosol formation in SARS-CoV-2 is assumed, even if not yet the latest scientific evidence available ist", explains Clemens Wendtner, chief physician, Schwabing in Munich clinic. "A crucial missing link is currently the direct detection of viable Virus in the air and in the exhaled air. Nevertheless, talk of the American scientists as a warning of that already when you Exhale a risk to the immediate environment due to SARS-CoV-2 aerosols could cause serious damage."
This would confirm the Thesis that the virus could spread through respiratory air, would discuss a mouth guard duty again. Also, the National Academy of Sciences Leopoldina recommends, according to the Wendtner is now a nationwide use of the mouth-nose cover or in a public space. "It is clear that this is more of a foreign protection and less a self-protection in the foreground, but the consistent use of the measure could entstehen" in the sum is also a self-protection;, the physician explained.
The US researchers of the NAS-related in your letter, a study that comes to a similar conclusion. It comes from researchers led by Nancy Leung of the University of Hong Kong and is on 3. April in the journal "Nature Medicine" appeared. Leung and colleagues analyzed the Transmission of the novel Coronavirus, but the spread of already known human corona viruses, Influenza and rhinovirus, breathing air.
They came to the conclusion that surgical face could help masks to avoid Transfers, if they are worn by Sufferers.
Find out more:
- Scarves, shawls, masks – Germany Needs a mouth-guard duty? What speaks in favour of the
Thomas Mettenleiter, President, Friedrich-Loeffler-Institute in Greifswald, you can understand the reasoning of the US-Americans in your letter: "The statements are based on the available information correctly." However, there is a need for further studies to understand the possible mode of Transmission better.
"Being proactive is often better than hesitating Abwarten"
In the clinic, you can not wait for this evidence. "From the clinical point of view is also already on the suspicion that infection might be capable of aerosols in the air of the room of a patient with Covid-19 available, traded without the outstanding scientific proof of the Infectivity abwartet", Wendtner explained. This applies, among other things, for intensive care units non-invasive ventilation, oxygen therapy, because in this therapy, high aerosol concentration in the ambient air would occur. 
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