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What scientists do and don’t know

Women using AbSecent scent products

One way to treat COVID-19 survivors who lost their sense of smell is: ‘Scent training’ where they learn defining scents like rose and lemon.Credit: Christine E. Kelly

Early in the COVID-1

9 outbreak, many people infected with the SARS-COV-2 virus lost their sense of smell, even without showing any other symptoms. Researchers also discovered that infected people could lose. Taste sensations and the ability to detect chemically stimulated sensations, such as spiciness called chemesthesis.

Almost a year later, some people have yet to regain these sensations, and for the proportion of people whose smell is volatile: unpleasant smells have replaced the usual pleasant scents. nature Explore the science behind the potential, long-standing, and destructive phenomena.

How many people with COVID-19 lose their sense of self?

The exact percentages varied between studies. But most suggest that the loss of smell is a common symptom.

One review published this past June.1 Data were collected from 8,438 people infected with COVID-19 and found that 41% reported loss of odor. In another study, published in August.2A team led by researcher Shima T.Moein from the Institute for Basic Sciences Research in Tehran, Iran, conducted an odor identification test on 100 COVID-19 patients, who were smelling it and identified. It is a basic multiple-choice. Ninety-six percent of the participants had an olfactory disorder and 18% had total odor loss. (Also known as anosmia)

“Usually, these patients say they have a sudden loss of smell,” said a clue that this condition is linked to COVID-19, Moin said. And often times, the disorder is the only COVID-19 symptom people have registered, indicating that the phenomenon is separate from a viral stuffy nose.

Some researchers say odor loss should be used as a diagnostic test for COVID-19, a study published last October.3 Self-reported changes in smell or taste were found to be a better predictor of transmission than other government-monitored indicators, such as arrivals at hospital accidents and emergency departments.

Why do people with COVID-19 become sensitive to odors?

Although the mechanism is not fully understood. But there is also consensus that the loss of smell occurs when coronavirus infects cells that support nerve cells in the nose.

When the researchers first identified the loss of smell as a symptom of COVID-19, they were concerned that the virus was infecting olfactory neurons in the nose, which sent signals to the olfactory bulb in the brain and thus the virus could reach the brain. Autopsy study4 Of people who have had COVID-19, it was shown that the virus has entered the brain very little

A team led by Sandeep Robert Datta, a neuroscientist at Harvard Medical School in Boston, Massachusetts, found that5 The cells that support sensory neurons in the nose, also known as sustained cells, are probably what the virus is infecting.

Datta and his colleagues focus on cells. sustentacular because SARS-CoV-2 attacks by targeting a receptor called ACE2 on the surface of the cell and the living cells contain a large number of receptors. Neurons can’t smell This suggests that the corona virus infects support cells, making nerve cells weak and malnourished.

But there may be other ways in which COVID-19 causes a loss of smell. For example, the research team in Italy showed.6 The loss of smell and taste coincided with an increase in blood levels of the inflammatory signaling molecule called interleukin-6, and a post-mortem study published in December showed signs of Strong inflammation, such as leaky blood vessels in the olfactory tubes in people who have previously been infected with COVID-19.7.

Although scientists have a good understanding of the mechanisms involved in smell. But they have little idea how the corona virus affects flavors and chemicals. “Nobody knows this very well,” said John Hayes, a professor of food science at Pennsylvania State University. At Park University, which is studying the effects of COVID-19 on sensory chemistry. Chemistry taste and feel are different senses than scent, although all three are combined to tell humans how ‘flavored’ a food or drink is. The therapy relies on ion channels on the sensory nerves in conjunction with other mechanisms, and the response to COVID-19 has not been studied well.

How quickly did the senses come back?

For most people, the flavor and chemistry will recover within a few weeks. In a study published last July872% of people infected with COVID-19 with olfactory dysfunction reported that they recovered after a month, as did 84% of people with taste disorders. Claire Hopkins, an ENT consultant at Guy’s and St Thomas’ Hospital in London, United Kingdom, and her colleagues also observed.9 Rapid recovery: Following 202 patients for one month, 49% reported complete recovery during that time, and 41% reported improvement.

But for others, the symptoms are more serious. Some people whose consciousness doesn’t immediately return will improve slowly over a longer period of time – and that can have consequences, Hopkins said.As a person gets their sense of smell, the smell often becomes unpleasant. And unlike what they remember, a phenomenon known as parosmia “everything smells like” for these people, Hopkins said, and the effect can last for months. This could be because olfactory neurons are working again as they recover, she said.

The other patients remained fully dyspnea for several months, and it is not clear why. Hopkins pointed out that in these cases, coronavirus infection might kill olfactory neurons.

How does permanent loss of chemistry affect a person?

Although the condition is not as well studied as other sensory loss, such as vision and hearing. But the researchers know the consequences can be severe.

One of the effects is that it exposes people to dangers such as food poisoning and fires. For example, people with anemia will be less likely to detect spoiled food and smoke. A 2014 study found that people with anosmia were more than twice as likely to experience dangerous events, such as eating spoiled food due to the odorless people.10.

The other effects are more difficult to measure. “Most people reject the importance of smell in life – until they lose it,” says Moein. Failure to appreciate the taste of food is a huge loss. But other feelings are also important.For example, Hayes points out a loss that parents will feel they can’t connect with their child through. ‘Newborn smell’ and Moein said odor disorders are linked to depression, although the biological mechanisms involved are unclear.

Is there any treatment to restore these feelings?

Lack of research means few available treatments. But one option is a scent practice, where people will sniff a regularly scheduled scent to learn new ones.Hopkins is working with a charity called AbScent in Andover, UK, to publish to the public about this training there is evidence.11 From before the epidemic that could improve odor function in some people with such disabilities But it doesn’t seem to work for everyone.

The available drugs are much more limited, Hopkins said, but for those in the early stages of COVID-19 infection, when the majority of the odor loss may be due to nasal cell inflammation, steroids may be helpful. According to the Hopkins team’s preliminary experiment12.

In long-term research, Richard Costanzo and Daniel Coelho of Virginia Commonwealth University in Richmond are developing an olfactory transplant device, a device implanted in the nose that senses odor-causing chemicals and sends electrical signals to the brain. However, the device is still going “many more years” in clinical presentation, Coelho said. In particular, researchers have to find out which brain regions should be activated, he added, so “there is still some science to be done. The ”

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