Can you smell diseases

Covid-19 symptoms: smell and taste disturbed

Status: 04/08/2020 4:20 p.m. | archive
The coronavirus affects the smell and taste of some sick people.

Typical symptoms of Covid-19 disease include fever, sore throat, extreme back pain, cough, chest pain, and extreme physical weakness. Another symptom occurs with remarkable frequency in the course of the disease: Many sufferers lose their sense of smell and taste for days.

Smell and taste disturbed for days

In a recent study from Belgium on 417 people who were suffering from a mild form of Covid-19, 86 percent of those surveyed reported impairment of their sense of smell, 88 percent had lost their sense of taste. Most of the symptoms disappeared completely after two weeks. In fact, in some cases, loss of taste and smell was the only symptom of the condition. In contrast to other colds, those affected often taste and smell nothing for days - without the nose becoming swollen.

Nerve involvement in coronavirus infection underestimated?

Neurologists suspect that the impairment of the sense of taste and smell could be triggered by a coronavirus attack on the nerves - an aspect that may have been underestimated with Covid-19 so far.

The thought is obvious: The dangerous coronaviruses Sars-CoV and Mers-CoV, which are related to the new virus, had also attacked the nerves.

The Sars-CoV pathogen from 2002 and the new Sars-CoV-2 are very similar. They enter the cell through the same receptor. And so it stands to reason that some symptoms of Covid-19 could also be traced back to a neurological cause. However, this has not yet been proven.

Sick people report "hallucinations"

Some sufferers report downright hallucinations: for example, they suddenly smell things that are not there - such as pus or fried bacon. One possible explanation for this are disorders in the olfactory center. With Sars-CoV, the predecessor of the new Sars-CoV-2, researchers found in animal experiments that the viruses penetrate into the olfactory center of the brain via nerve endings in the nasal mucosa and the olfactory nerve.

Attack on the respiratory center in the brain?

Sars-CoV not only attacked the olfactory center, but also the brain stem and thus the respiratory center. Experts suspect that in some Covid 19 sufferers, the sudden lung failure could be due to a brainstem disorder. The viruses could penetrate from the lungs via the spinal cord to the brain and trigger respiratory arrest in the respiratory center.

In studies with Mers-CoV, it was found that animals also died of lung failure that had previously shown no symptoms in the airways. The viruses were found in these animals only in the brain, but not in the lungs. That was a clear sign that the viruses had attacked via the nervous system.

Prevent lung failure in Covid-19

With Covid-19, too, there are repeated cases of acute lung failure. Doctors cannot currently investigate whether the brainstem is also involved in the disease, as the sick are treated in isolation wards and cannot be taken to the magnetic resonance imaging required for this.

How big the effects of Covid-19 is on the nervous system has yet to be researched. Scientists hope to soon find a so-called marker that they can use to detect the virus in the tissues of the deceased.

Nerve Involvement in Covid-19: Consequences for Treatment

A proven involvement of the nerves in a Covid 19 disease would have decisive consequences for the therapy. So far, doctors have decided whether a patient needs ventilation or not based on the condition of the lungs alone. If the lungs appear normal, but the brain stem is attacked, it could be fatal not to ventilate the affected person anymore.

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Experts on the subject

Prof. Dr. Christian Gerloff, director
Clinic and Polyclinic for Neurology
Head neurocenter
University Medical Center Hamburg-Eppendorf
Martinistrasse 52
20246 Hamburg

Prof. Dr. Peter Berlit, Secretary General
German Society for Neurology e.V.
Reinhardtstrasse 27 c
10117 Berlin

Prof. Dr. Marylyn Addo
Head of Infectious Diseases Section
I. Medical clinic and polyclinic
University Medical Center Hamburg-Eppendorf
Martinistra├če 52, 20246 Hamburg

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