As of mid-June 2022, more than 9 million people have been infected with the new coronavirus in Japan.

Many people suffer from various illnesses even after recovering from corona, and are considered to be "sequelae."

What kind of symptom is a sequela, how long it will last, and how it develops.

I have summarized what I have learned.

I have recovered from corona, but I have various symptoms ...

Some people have been suffering from poor health for a long time after recovering from the new Corona.

A man in his twenties living in Saitama Prefecture was infected with corona in late July.

A man who worked as a sales position at an IT-related company in his first year as a member of society.

He had a fever of over 39 degrees and had symptoms such as headaches, dullness, and no taste or smell.

After two weeks of medical treatment at the hotel, he recovered, and his fever and inability to breathe gradually disappeared, but his malaise, odor and taste abnormalities continued.

Then, in August, he returned to the company.

He was tired and coughing, and his taste and smell didn't return, so he wasn't satisfied with his diet.

Furthermore, in September, his head became "haze" and his thinking ability deteriorated, and he could not write simple emails.

Due to stress, he couldn't sleep easily and continued to feel depressed, and was diagnosed by a psychiatrist as "depression caused by corona".

Around this time, he was diagnosed with "sequelae" at an outpatient clinic to see the aftereffects of Corona.

The man took a leave of absence and devoted himself to treatment.


"Can I continue to be an office worker in the future? I had symptoms of depression and was confused as to whether this was really me."

After that, the man's symptoms subsided a little and he returned to work in March last year, about nine months after the infection.

However, he did not recover as he did before the infection, he continued to feel tired, and he often felt nausea in his daily life. In October last year, he was diagnosed with adjustment disorder by a psychiatrist.

He felt physical and mental limitations and ended up retiring.


"There were quite a few people who got infected at the company after I got infected, but in most cases, the vaccines and medicines helped me to get rid of the aftereffects quickly. Why are you so long? I was trying my best to heal myself, but sometimes I felt a little tight because my feelings didn't mesh with my surroundings. There was also nothing. I couldn't keep up with my feelings and body, and the mental damage was great. "

“Corona sequelae” may last for a long time

WHO = The World Health Organization defines "corona sequelae" as "symptoms that usually appear within 3 months of the onset of the new corona and last for at least 2 months, which cannot be explained as symptoms of other diseases."

It can last for a long time and is called "Long COVID" in English.

The main symptoms are said to be malaise, shortness of breath, memory impairment, poor concentration, and impaired sense of smell and taste.

How long will it last?

A research group of the Ministry of Health, Labor and Welfare led by Professor Akihito Yokoyama of Kochi University interviewed doctors and surveyed patients nationwide for more than 1,000 people with moderate or higher illness who were hospitalized during the year until September last year. So, I checked every three months to see what kind of symptoms I had.

At 3 months after infection,

about 50% of people had muscle weakness,

30% had dyspnea

, 25% had malaise,

20% had sleep disorders, and

▽ decreased thinking ability. Myalgia and coughing were about 18%.

Some had multiple symptoms.

The number of people who complain of symptoms tends to decrease over time, and one year later,

10.1% of people have sleep disorders,

9.3% have muscle weakness,

6.0% have dyspnea , and

5.3 have decreased thinking ability .


▽ cough was 5.0%,

▽ malaise was 4.9%, and

▽ muscle pain was 4.6%.

13.6% of the respondents complained of some kind of symptom.

People with severe respiratory symptoms tended to have more sequelae.

In addition, a research group of the Ministry of Health, Labor and Welfare led by Professor Koichi Fukunaga of Keio University has targeted more than 1,000 patients, from patients who were mildly ill to severely ill in Corona, to what extent in one year from the diagnosis, aftereffects. I checked the patient's questionnaire to see if it was found.

According to this, even one year later,

▽ people who complained of malaise were 12.8%,

▽ dyspnea was 8.6%,

▽ muscle weakness and concentration were 7.5%,

▽ memory disorder was 7.2%,

▽ Sleep disorder 7.0%,

▽ arthralgia 6.4%,

▽ muscle pain 5.5%,

▽ smell disorder 5.4%,

▽ tan 5.2%,

▽ hair loss 5.1%,

▽ headache 5.0%,

▽ taste disorder 4.7 %,

▽ Cough was 4.6%,

▽ Numbness of limbs was 3.9%,

▽ Ophthalmic symptoms were 3.6%.

It is said that 33% of the people complained of some kind of symptom.

(* Detailed data is posted at the end of the sentence)

The two research groups have different research methods, and while the research group at Kochi University conducted questionnaires to patients and interviewed doctors, Keio University Since the research group is based on patient questionnaires, it seems that there is a difference in the frequency of symptoms.

In addition, neither research group has made comparisons with non-infected people, so it cannot be determined whether the individual symptoms are sequelae of corona.

Various treatments have been tried for these symptoms, but none are specific, and symptomatic treatment according to the symptoms is used.

How far are the aftereffects?

However, the symptoms included in the WHO-defined "corona sequelae" are diverse, and there is debate among national experts as to whether they are all caused by corona.

Professor Akihito Yokoyama of Kochi University, who was the representative of the research group of the Ministry of Health, Labor and Welfare, points out that it is difficult to judge at this time whether it is a sequela of corona or another symptom that occurred after the infection of corona.

(Professor Akihito Yokoyama, Kochi University)

"In our research, there is no comparison of how many symptoms occur in uninfected people, so it is very difficult to tell whether it is a sequela of corona. At least the lungs. People who have an abnormality in the image and complain of suffocation are likely to have sequelae, but the current situation is that it is not clear to what extent the sleep disorder and mental illness are caused by corona. There may be other causes, and if you do not make a proper diagnosis, the patient will suffer disadvantages. While it is said to be a sequela of corona, there may be other illnesses that can be cured. In the future, I think it will be necessary to compare healthy people and people with non-corona pneumonia with those with corona to get a more accurate picture of the situation. "

What is the mechanism of sequelae?

How well do you know the mechanism by which various symptoms persist even after recovering from corona?

Professor Akiko Iwasaki of Yale University, who specializes in immunology, says that four hypotheses are influential.

(1) Even if the initial symptoms such as coughing and fever subside, the remaining virus and its fragments are inflamed for a long time

(2) The immunity that should protect the body is attacking one's body

(3 )

) Prolonged repair of organs damaged by infection

(4) Reactivating viruses that have existed in the body for a long time, such as herpes virus.

These factors combine to cause various symptoms. It is thought that it is.

Professor Iwasaki is concerned that these symptoms are not limited to people who have become severely ill with corona.

A study conducted in the United States found that 75% of people who complained of long-term symptoms were not hospitalized at the time of corona infection, and even asymptomatic or mild cases are at risk of developing corona sequelae. ..

(Professor Akiko Iwasaki, Yale University)

"I think the most likely thing is that the virus is lurking somewhere, causing inflammation and causing various symptoms in other organs. I'm thinking now. "" Some people who have no corona symptoms start to develop symptoms like long covid (aftereffects) after a few months. The rate of aftereffects in those who have been vaccinated. There are reports that the rate is low, but the rate varies depending on the report. I don't think I can be relieved just because I got the vaccine. "

What is "brain fog" that reduces thinking ability?

In addition, as one of the sequelae of corona, it is said that there is a symptom called "brain fog" that makes you feel that your head is haze and your thinking ability is reduced.

Professor Yoshiyoshi Shimohata of Gifu University, who specializes in neurology and was also involved in the preparation of the "medical care guide" of the Ministry of Health, Labor and Welfare regarding sequelae, said that "Brainfogue" often does not show any abnormalities in MRI or blood tests. He points out that it is difficult to make a judgment even in the field.

On the other hand, research is progressing on why it is caused.

(Professor Yoshiyoshi Shimohata, Gifu University)

"What we have learned from overseas animal experiments is that autoantibodies that infect the new corona and cause inflammation throughout the body and attack one's body, and cytokines that cause inflammation. It means that a substance called is formed. It is thought that it may be caused by getting into the bloodstream and going to the brain to cause inflammation. Now that there is only symptomatic therapy, understand the mechanism and treat it as well. It is important to make improvements. "

Omicron strain There are few aftereffects, but ...

Since entering this year, the infection of the Omicron strain has spread, and people who have been infected by an order of magnitude compared to the spread until last year have been infected.

How well do you know the sequelae of the Omicron strain?

The Tokyo Metropolitan Government has set up a consultation desk for the aftereffects of the new corona at metropolitan hospitals, etc., and summarizes the symptoms of more than 2,000 people who received the symptoms during the four months up to April.

According to this,

▽ people who complained of coughing were 38.6%,

▽ malaise was 34.0%,

▽ abnormal taste was 10.6%, and

▽ abnormal smell was 9.5%.

(* Detailed data is posted at the end of the sentence)

It is analyzed that abnormalities in taste and smell and hair loss are significantly reduced compared to people infected with Delta strains.

In addition, a group at the National Center for Global Health and Medical Sciences published research results comparing people infected with the Omicron strain with those infected with the previously spread virus according to conditions such as age, gender, and vaccination history. ..

As a result, only about one-tenth of the Omicron strains had symptoms that seemed to be sequelae.

However, it is pointed out that the number of infected people of Omicron strain is extremely large, so there is a possibility that more people will suffer from sequelae in the future.

According to UK government data, the frequency of people complaining of sequelae is about half that of Delta strains in Omicron strains if they have been vaccinated twice.

So far, there have been no reports of the Omicron strain having longer-lasting symptoms.

Care for patients with sequelae

The man in his twenties, who was introduced at the beginning, had symptoms such as malaise and nausea for nearly a year and a half after being infected.

Around January 2022, after the symptoms have generally subsided, he learned the basics of programming at a vocational training school and is thinking of working as a system engineer in the future.


"I'm really glad that my physical condition has finally returned to normal. However, my physical strength has not completely returned to the previous 80%, so I'm looking for a way to work comfortably."

At present, there are still many unclear points about how much corona sequelae are and how they are caused, but the two specialists who are examining patients have taken care of those who have symptoms. It points out the importance.

(Professor Akihito Yokoyama, Kochi University)

"It is true that some people are suffering from symptoms regardless of the cause, and it is necessary to deal with patients properly."

(Professor Yoshiyoshi Shimohata, Gifu University)

"Actually the brain While some people are inflamed, the reality may be quite complicated, as they may be suffering from their own symptoms and worsening their symptoms mentally. Whatever the cause, the patient I think it is important to support them firmly. Since it is a new symptom, we will spend money on research properly, create a specialized medical center, etc. to support patients mentally and society. It is also necessary to understand the actual situation properly. "

★★ Details of the data introduced in the article ★★

Survey by the Ministry of Health, Labor and Welfare research group centered on Keio University

Tokyo data