The number of new infections with the rapidly expanding new coronavirus has begun to decline nationwide.



However, the rate of decline is slow, and the number of severely ill and fatalities continues to increase.



What are the symptoms and sequelae of the Omicron strain?


And the point that "the infection has peaked out" has begun to be heard from experts.



I have summarized what I have learned.



(As of February 16, 2022)

More than double the number of infected people in half the period of Delta strains

In the sixth wave of the spread of infection by the Omicron strain, the number of newly infected people has continued to increase for more than a month.



Even in the fifth wave of infection in the summer of 2021, when the Delta strain spread, the number of infected people was about 900,000 in the three months from July to September.



In the sixth wave, the number of people exceeded 2.3 million in the first month and a half.



In half the period of the Delta strain, the number of infected people has more than doubled, and the number of infected people has increased significantly.



However, in mid-February 2022, the number of reported cases began to decline.


As of February 15, the number of newly infected people nationwide in a week was 0.90 times that of the previous week, and experts began to point out that the infection had peaked.



In Okinawa Prefecture, where the infection spread earlier in Japan, the average number of infected people per week reached the highest level of about 1440 on January 18, and then began to decline.



However, even on February 15, there were about 560 people.



In the first two weeks of January, the number of infected people increased by 40 times at a stretch, but in the following month it was less than half of the peak, but the speed of decline is slowing down. increase.



Looking at the tendency of overseas infections to spread before Japan, in the United Kingdom, the number of newly infected people in a week exceeded 1 million around January 10, and then in the week until January 18th, it was about. The number was 674,000, a decrease of about 40% compared to the previous week.



After that, it remained flat for about two weeks, but in the week until February 15, it has decreased again to more than 368,000.

In the United States, according to the CDC = Centers for Disease Control and Prevention, the number of new infections per day exceeded 1.3 million on January 10, with an average of 800,000 per week.



After that, it gradually decreased, and as of February 14, the average number of newly infected people per week has decreased to more than 146,000.



Overseas, the rate of booster vaccination is 55.5% in the United Kingdom and 27.7% in the United States, and the scale of infection spread is larger than in Japan, and the number of people with immunity is increasing, so the infection is rapidly decreasing. It is believed that it is in the background of the infection.


(Data is Our World in Data as of February 14)

The number of deaths may exceed the 5th wave

The number of infected people in Japan is about 2,337,000 in the month and a half from January to February 15, 2022, when the Omicron strain spread.



During this time, 2367 people have died, with a case fatality rate of approximately 0.10%.



Although the Omicron strain has been considered to be less likely to become severe, the scale of infection is so large that the number of severe cases and deaths is increasing.



The number of deaths reported on the 1st was 34 on January 26, 2022, three weeks ago, but on February 4th it was 103 and exceeded 100, and on February 8th. The number was 159, and on February 15th, it was 236, a record high.



It continues to be higher than 89 on September 8, 2021, which was the highest number during the period when Delta stocks spread.



In the spread of infection so far, the number of severely ill cases has peaked about two weeks after the peak number of infected people, and then the number of deaths has peaked.



During the Delta stock period, 3073 people died in the three months from August to October last year, and there is a possibility that the Omicron stock will surpass in the sixth wave.



In Japan, the fifth wave of last summer when the Delta strain spread was the timing of advanced vaccination, so it is said that the vaccine was able to prevent the death of many elderly people.



Although two vaccinations have the effect of preventing aggravation to a certain extent, the infection of the Omicron strain spreads to the elderly and the number of people who become aggravated increases when the effect diminishes after a while. Is believed to be.

The bed usage rate is increasing day by day, and as of February 15, it is 84.3% in Osaka prefecture and 58.8% in Tokyo.



In Okinawa prefecture, it is 48%, which is decreasing little by little.



In addition, there are cases where it is difficult to transport emergency patients other than the new coronavirus, and according to the summary of the Fire and Disaster Management Agency of the Ministry of Internal Affairs and Communications, it is difficult to transport patients, such as four or more inquiries to the hospital before the destination is decided. The number of “cases” was 5,740 in the week leading up to February 13, the highest number ever for five consecutive weeks.

In the United States, CDC data continue to report more than 2000 deaths per day, except on weekends when reports are low.



According to the CDC, although the severity of the Omicron strain is low, the number of inpatients is increasing, which puts a burden on the medical system and the number of deaths is considerable.



According to "Our World In Data", a website run by researchers at Oxford University in the United Kingdom, the number of deaths per day will be in the week until February 14th.


▽ About 2300 people in the United States,


▽ About 320 people in France,


▽ About 150 people in Japan, etc.



At the time of Delta stocks,


▽ in the United States, about 2000 people in late September 2021 and


▽ in France, about 110 people in late August peaked, which is now above the level at that time.



Denmark, which has taken steps to ease restrictions on activities, has a population of about 5.81 million, which is about the same size as Hyogo Prefecture, but the number of deaths reported per day was 41 on February 14, the highest in Denmark so far. It is in line with the high level of January 2021.

What kind of person is getting sick?

It is said that many people with severe illness are elderly or have underlying illness.



According to the materials submitted to the expert meeting of the Ministry of Health, Labor and Welfare, the rate of worsening pneumonia and becoming "moderate 2" or higher requiring oxygen administration from January 1st to 20th, 2022 became severe. It was 0.09% for those without the risk factor, but 1.22% for those with the risk factor, which is more than 13 times higher.



Risk factors include "chronic obstructive pulmonary disease," "diabetes," "lipidemia," "hypertension," "chronic kidney disease," "cancer," "obesity," and "smoking." The percentage of people with moderate disease 2 or higher is as high


as 0.81% for one risk factor


, 2.13% for


two, 3.63% for


three, and 4.70% for four or more. I was there.



By age,


▽ people with one risk factor under 40 years old are 0.155%,


▽ people in their 40s are 0.37%,


▽ people aged 50 to 64 years old are 0.61%, and


▽ people aged 65 and over are 4.43%. It was getting higher as I got older.

Significant hospitalization risk due to additional vaccination ↓

New data have been released by the CDC on the effectiveness of booster vaccines.



The CDC is based on data from approximately 240,000 patients who visited emergency outpatient clinics at hospitals throughout the United States from late August 2021 to late January 2022, and approximately 93,000 inpatients. The results of an analysis of the effects of vaccines for people over the age of 18 were published in the weekly report dated February 11.

According to it, the effect of Pfizer and Moderna's "mRNA vaccine" to prevent hospitalization compared to non-vaccinated people is up to 2 months after the third booster vaccination during the Delta strain period. It was 96%, and even after 4 months or more, it was 76%.



At the time of the Omicron strain, the effect of preventing hospitalization was 71% from the second inoculation to 2 months, and 54% after 5 months or more, but when the third inoculation was performed, Omicron was used. The effect of preventing hospitalization was also improved for the strain, which was 91% within 2 months after inoculation and 78% within 4 to 5 months.



The CDC states that a third dose is important and that unvaccinated people should be vaccinated as soon as possible.

Inflammation of the upper respiratory tract and symptoms of cough and throat nose

Regarding the Omicron strain, the WHO = World Health Organization says that although it is prone to inflammation of the upper respiratory tract such as the nose and throat, for many people, the risk of reaching the lungs and becoming severe is lower than other mutant viruses.



As of January 24, the National Institute of Infectious Diseases has released data on more than 3,600 people registered in the system "HER-SYS" that aggregates information on people infected with the new coronavirus.



At the time of notification, the symptoms seen with Omicron strains were


▽ fever 66.6%,


▽ cough 41.6%,


▽ general malaise 22.5%,


▽ headache 21.1%,


▽ non-cough respiratory symptoms 12.9%,


▽ Nausea and vomiting are 2.7%, and


diarrhea is 2.3%.



So far, 0.8% of people have complained of the olfaction and taste disorders that are characteristic of the new coronavirus.



Other domestic and overseas surveys have also shown symptoms of cough and sore throat, runny nose and stuffy nose, and the Japanese Society of Otolaryngology Head and Neck Surgery is suffering from hay fever every year as it is confusing with the symptoms of hay fever. People who have hay fever are encouraged to see a medical institution as soon as possible before symptoms appear.

Increasing number of infected children and the elderly

Omicron strains are more prevalent in children and the elderly.



According to the website of the Ministry of Health, Labor and Welfare, the number of newly infected persons under the age of 10


was 149 in the week until December 28, 2021, but


353 by January 4, 2022,


▽ 1 .

2238 people by January 11th,


▽ 12,947 people by January 18th, ▽ 41,863 people by


January 25th, ▽


67,564 people by February 1st,


▽ until February 8th The number continues to increase to 76,856.



In the United States, approximately 4.5 million children have been confirmed infected since the beginning of 2022.



The number of newly infected children in the week up to February 10 was about 300,000, a significant decrease from the peak of about 1.15 million in the week up to January 20.



Still, it's more than the time of Delta stocks.



The American Academy of Pediatrics reports that children with severe symptoms have a rate of 0.1 to 1.5% hospitalization and a mortality rate of 0 to 0.01%.

In addition, the number of infected elderly people is increasing.



The number of infected people in their 60s and above


was 379 in the week until December 28, 2021, but


513 by January 4, 2022,


3685 by January 11, and


▽ .

By January 18, there were 13,867 people, by


January 25, there were 35,500 people, by


February 1, there were 60,732 people, and by


February 8, there were 75,696 people. ..



The majority of those who die are elderly, and according to the Ministry of Health, Labor and Welfare, of the 817 people who died in about one month from January 5 to February 8,


▽ 90s and over are 34.4%,


▽ 80 .

36.6% are in their


70s, 19.6% are in their 70s


, 4.0% are in their 60s, and


94.6% are in their 60s or older.



Shigeru Omi, chairman of the government subcommittee, said on February 10, "In Omicron strains, the places of infection are diversifying not only in restaurants but also in homes and workplaces. It is polarized, and some people are becoming more serious. There is a need for a medical and health system that focuses on those who are at risk of becoming seriously ill, and infection control is meaningless only at restaurants. We need to shift to a wider range of measures. "

Verification of sequelae of Omicron strain is yet to come

It is not yet known how much sequelae will occur after infection with the Omicron strain.



Regarding the sequelae of the new coronavirus called "Long COVID," WHO states that "a symptom that begins 3 months after the onset and lasts for at least 2 months."



With the conventional new coronavirus, about 10% to 20% of people who experience infection have sequelae such as malaise, shortness of breath, and cognitive dysfunction, which are said to "generally affect daily life."



"There seems to be no connection between the severity of the initial infection and the subsequent sequelae," he said.



It's only been about three months since the Omicron strain was first reported in South Africa, and research on sequelae is yet to come.



Interest is growing overseas as well, and verification is expected to proceed.

What I learned from "BA.2"

A mutant virus called "BA.2", which is one of the strains of the Omicron strain, has begun to be reported not only in quarantine but also in the market in Japan.



However, according to the material presented by the National Institute of Infectious Diseases to an expert meeting of the Ministry of Health, Labor and Welfare on February 15, "sustainable replacement has not been observed" as of the first week of February.



Omicron strain "BA.1", which is spreading all over the world, has a part missing in the protrusion "spike protein" on the surface of the virus, but "BA.2" lacks this part. I know there are no parts.



Omicron strains may not be detected by some of the overseas inspection methods, and they are sometimes called "stealth omicrons", but in Japan they can be detected by another method, so this name is used. It is said that it will not hit.

"BA.2" is believed to be even more infectious.



According to a laboratory under the Danish health authorities, "BA.2" was about 20% of the new coronavirus detected in Denmark in the last week of 2021 in 2022 1. It is said that it was about 66% in the week from the middle of the month to the end of the month.



According to the health authorities in the United Kingdom, the number of mutant viruses that are considered to be "BA.2" in the United Kingdom increased from 5.1% on January 24, 2022 to 18.7% on February 6.



During this period, the percentage of "BA.1" decreased from 94.9% on January 24th to 81.3% on February 6th.



The average "onset interval" between the onset of one infected person and the next onset of the infected person was 4.09 days for the Delta strain, but 3.72 days for the Omicron strain "BA.1". , "BA.2" has an average of 3.27 days, which is about half a day shorter than "BA.1", and it is possible that it is related to the rapid spread of infection.



On the other hand, although the data is still limited, there have been no reports of cases of re-infection with "BA.2" after being infected with "BA.1".



Experts say that the effects of "BA.2" may not reduce the number of infections.



According to WHO, there is no evidence that the risk of aggravation due to "BA.2" is higher than that of "BA.1".



Regarding the effect of the vaccine, the British health authorities said that the effect of the vaccine to prevent the onset was 9% in "BA.1" 25 weeks or more after the second vaccination, and about half a year or more later. 13% for ".2", 63% for "BA.1" two weeks after the third booster vaccination, and 70% for "BA.2", indicating that there was no difference in the effectiveness of the vaccine. ..

Comparison with previous mutant viruses

Based on information from WHO, the National Institute of Infectious Diseases, and public institutions in each country, what is known now, such as infectivity and pathogenicity, is compared with other "variant of concern = VOC". I summarized it.

▼ Infectivity

According to the WHO weekly report, the Omicron strain is more susceptible to spread than previous mutant viruses.

▼ Pathogenicity

Omicron strains are said to have a lower risk of hospitalization and aggravation than Delta strains.



However, the scale of the spread of infection is large, and the number of hospitalized people and the number of people who are becoming more serious are increasing, and the burden on medical institutions is increasing.

▼ Risk of reinfection

WHO states that the Omicron strain has mutations that make it easier for people with immunity to re-infect due to vaccines and past infections.



Imperial College London in the United Kingdom reports that the risk of reinfection with Omicron strains is 5.41 times higher than with Delta strains.

▼ Vaccine effect (Pfizer Moderna's mRNA vaccine)

According to data from the UK health authorities, Pfizer and Moderna mRNA vaccines for Omicron strains dropped to about 10% after 20 weeks from two doses, but Pfizer or Moderna boosters were given. Then, after 2 to 4 weeks, the effect of preventing the onset increased to 65% to 75%.



The effect of reducing the risk of hospitalization due to severe illness is higher than the effect of preventing the onset.

Analysis of people vaccinated with Pfizer, Moderna, and AstraZeneca shows that the effect of preventing hospitalization is 72% for 2 to 24 weeks after two vaccinations and 52% for more than 25 weeks, 3 After the second booster vaccination, it was 88% after 2 weeks.

▼ Effect of therapeutic drug

重症化を防ぐために感染した初期に投与される「抗体カクテル療法」は、効果が低下するとされ、厚生労働省はオミクロン株では投与を推奨しないとしています。

一方で、軽症患者用の飲み薬「ラゲブリオ(一般名モルヌピラビル)」や、新たに承認された「パキロビッドパック(一般名ニルマトレビル/リトナビル)」、それに軽症から重症の患者まで投与される「レムデシビル」など、ウイルスの増殖を防ぐ仕組みの飲み薬には影響が出ないと考えられています。

また、WHOは、重症患者に使われる免疫の過剰反応を防ぐ薬やステロイド剤は、引き続き効果が期待されるとしています。

専門家は

厚生労働省の専門家会合のメンバーで国際医療福祉大学の和田耕治教授は「拡大傾向はいま落ち着きつつあるが、多くの地域で高止まりしていて、本当に減少局面に入るかどうかもう少し注視が必要だ。オミクロン株でも、特に75歳以上の高齢者では、感染すると重症化し、亡くなる人も増えてきている。高齢者施設での感染が依然として多いので、こうした場所で3回目のワクチン接種をどれくらい速く行えるかも今後の重要なポイントだ」と話しています。

また、厚生労働省クラスター対策班参与で、数理モデルに詳しい古瀬祐気医師は「感染状況はピークが見えてきたところかなと思っている。通常の医療が提供できなくなってきたところが出始めたことに市民が気付き、いまは我慢するときだと行動を変えたことが背景にあるのではないか。ただ、3月には卒業や入学、入社や異動、歓送迎会など人との接触が多くなる季節がやってくるので、感染者数が減りきらないまま流行が長引いたり、すぐに第7波が始まったりする可能性もある。特に、まだ1回目、2回目のワクチンを打っていない人は、オミクロン株に感染しても良い免疫ができないと言われているので、いまからでも接種してほしい」と話しています。

対策は変わらない

Experts are calling for more thorough measures as the situation continues where it is safe to get infected.



Even with the Omicron strain, the infection route is the same as before, and the main infections are infection by flying, and very small flying flying in a closed room called "micro flying" or "aerosol".



There is also contact infection by touching the nose or mouth with a hand with the virus.



Omicron strains were also infected through eating and drinking, such as year-end parties with colleagues at work at restaurants and dinner with relatives at home, and cases of infection through work in a dense environment at work were also reported. I am.

The chairman of the government subcommittee, Mr. Omi, said that the number of infections was much higher than expected in situations where the mask was removed or inadequately worn, such as a "nose mask," and he called for a non-woven mask to cover the nose. increase.



In addition to vaccination, the Ministry of Health, Labor and Welfare's expert meeting also calls for continued basic measures such as wearing masks, especially during conversations, disinfection and hand washing, and avoiding ventilation and tightness.

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