Delta virus will still make a comeback? The next peak in Japan may be in mid-February next year, and China must also prevent a new wave of infections in winter and spring. (Picture/ Visual China )
Source | Ifeng.com Cancer Information Bureau
The number of people in Japan increased from nearly 28,000 per day in September to just over 200 on October 31. Why did the Delta virus suddenly and mysteriously subside? Where did it go? ?
After experiencing the fifth wave of the epidemic, the largest in history, Japan's daily number of new cases fell rapidly.
On October 31, the number of new infections in Japan was 232, which was less than 1/100 of the peak of the epidemic on August 21. Within 2 months, the number of new daily cases in Japan dropped off a cliff.
From the first confirmed case of new coronavirus infection in mid-January 2020, to November 1, Japan had confirmed a total of 1.72 million infections and 18,000 deaths in this epidemic.
The epidemic in Japan in the past two years has been divided into five waves. The fifth wave that started in late July was the most infectious, with the number of infections and deaths reaching their peak. But in mid-September, Japan, which originally had more than 28,000 infected people a day, suddenly began to see a sharp decline.
It was the Delta virus that caused the fifth wave of the epidemic in Japan. Where did this new coronavirus variant that almost caused huge trouble to all countries go?
Even among several developed countries, Japan is the country with the most obvious decline in the epidemic. What is the reason behind this?
Japan’s National Institute of Genetics published a research article claiming that Delta virus may die naturally?
First, let’s take a look at the recent hot news on the Internet.
Major Japanese media reported that Professor Hisaro Inoue of the National Institute of Genetics of Japan said at a press conference that because the mutated enzyme that affects the repair of the delta virus has changed, the virus is likely to die naturally.
Specifically, it is an enzyme mutation called nsp14 that causes the virus to be unable to repair and eventually die. This is explosive news. If true, it will change the direction of the epidemic. This may even mean that the epidemic is coming to an end. But is this really the case?
This news is currently spreading a lot on the Internet in Japan and China. However, I personally cannot agree with this view. From the current research and basic biological principles, the mutation of nsp14 is not the main reason for the decline of the Japanese epidemic.
Let’s talk about nsp14 itself first.
To put it simply, the structure of the new coronavirus itself is nucleic acid plus a protein shell. The protein of the new coronavirus is divided into two parts: structural protein (structure protein) and non-structural protein (nonstructure protein, abbreviated as nsp).
structural proteins are the four types of S protein and N protein that we have heard a lot about. They are necessary proteins to form virus particles. There are more than a dozen non-structural proteins. They are encoded by virus genome and are used in virus replication. It has a certain function in the process, but it does not bind to the proteins in the virus particles. The full name of
nsp14 is "N-terminal 3' to 5' exonuclease (ExoNase), C-terminal N7 methyltransferase (N7-MTase)", (some friends may have fainted after seeing this name, okay Skip directly to the next paragraph), its N-terminal domain has error-correcting exonuclease activity, which mainly performs corrections during RNA replication and transcription to prevent lethal mutations (this lethality refers to the lethality to viruses) occurs, and the C-terminal domain is responsible for capping the mRNA. During the process of virus replication, four non-structural proteins, nsp7, nsp8, nsp12 and nsp14, constitute RdRp (RNA-dependent RNA polymerase ), which jointly affect virus replication. There may also be mutations in nsp14 itself, but not all mutations will lead to functional changes in nsp14.
If the replicase , including nsp14, undergoes a major mutation that affects virus replication, the mutated virus should disappear immediately. However, if we detect a large number of strains carrying mutant nsp14, it means that this mutated virus is spreading widely in the population, and the virus does not die when spreading and can maintain the ability to infect.
This means that the hypothesis that "mutation of nsp14 leads to the accumulation of mutations in the genome that cannot be repaired and eventually leads to the death of the virus" is contradictory from the perspective of virus evolution and survival. It is difficult for us to imagine that in many different Among infected people, this "lethal" mutation will occur at the same time or one after another in a short period of time.
Because generally speaking, when a fatal mutation appears for a certain species, this mutation will not spread within the species, but will be quickly eliminated. Only organisms that adapt to the mutation can survive, and self-destructive mutations will not occur at the same time. It appears in large numbers and is even less likely to be detected by us in large numbers.
Large-scale vaccination is late compared to other countries. Could this be another reason why Japan’s current wave of epidemic has subsided?
So, what is the main reason for the decline of the epidemic in Japan?
is actually not that mysterious.
Let’s talk about vaccines first.
Currently, 77% of the Japanese people have received at least one dose of new crown vaccine , and 71% have completed the full course of vaccination. The vaccination rate is higher among the elderly. 94% of people aged 80 to 90 have completed the full course of vaccination, even if they are centenarians This figure is also 86% among the elderly.
This is one of the important reasons for the sharp decline in the epidemic curve.
However, the vaccination rate cannot fully explain the changes in the epidemic in Japan.
Let’s look at vaccination rates and what’s happening in countries like Japan.
-Spain, the vaccination rate is 79%, and there are 2,000 new cases every day;
-Canada, the vaccination rate is 74%, and there are 2,600 new cases every day;
-Italy, the vaccination rate is 72%, and there are 2,600 new cases every day; 4,500 new cases;
- UK, full vaccination rate 68%, 40,000 new cases daily (no extra zero here).
Therefore, Japan’s vaccination rate cannot fully explain the decline in its epidemic. However, one thing that is special about Japan is that among these developed countries, Japan’s large-scale vaccination work was carried out relatively late.
More and more studies have shown that the level of neutralizing antibodies will decrease over time. Therefore, the earlier the vaccination is started, the lower the protection power of the vaccine will have on the population (without a booster shot); conversely The later it starts, the closer protection is to peak.
Therefore, the current vaccine protection for the Japanese population is still at its peak. For every 100,000 people in Japan, the number of unvaccinated infections is 23.7, while the number of fully vaccinated people is 2.
This data is not stratified (such as age, occupation, etc.), but if the efficiency is calculated directly, we can find that the vaccine's effectiveness in a real-world environment is as high as 92%, which is very close to the two mRNA vaccines. Phase III clinical trial data, and it is still the case that delta has become the main strain in Japan.
The Japanese government organized experts to study the reasons for the decline of the epidemic, and attributed it to these five major factors
Although the vaccine did play a key role in the sharp decline of the epidemic in Japan. However, for epidemic prevention and control, both vaccines and NPI are important. NPI is non-pharmaceutical intervention measures, such as washing hands frequently, wearing masks, maintaining social distance, and various social prevention and control measures.
The Ministry of Health, Labor and Welfare of Japan held a meeting at the end of September to discuss changes in the epidemic. Experts at the meeting believed that the decline of the epidemic in Japan may be attributed to five points -
- the disappearance of factors leading to the spread of infection;
- the medical crisis changes people epidemic prevention countermeasures;
-reduction in the number of people traveling at night;
-vaccination effect;
-weather impact.
Let’s expand on it:
1. The factors that led to the spread of infection disappeared:
The reason why the epidemic peaked in Japan from July to August was that in addition to the Olympic Games, it also encountered summer vacation, consecutive holidays, and Obon (a traditional Japanese festival) , these vacations have led to active crowd movement, making it easier for the virus to spread. These factors have now disappeared.
2. The medical crisis changes people’s anti-epidemic strategies:
During the peak of the epidemic in Japan, medical resources in some areas were saturated or even overrun, resulting in some infected people being unable to be admitted to hospital, and even some severely ill patients dying at home. The news of these medical crises has forced the public to become more cooperative in epidemic prevention - because people who seek death may actually die.
3. Reduction in the number of people traveling at night:
Due to the declaration of a state of emergency, the number of people in downtown Tokyo at night from mid-August to late September decreased by 25% to 40% compared to early July. If divided according to vaccination status, the decline in unvaccinated people in downtown areas at night is expected to be as high as 70%.
4. Vaccination effect:
We have also mentioned this above. We are focusing on the rapid increase in the proportion of vaccination among young and middle-aged people in Japan. Taking people aged 40 to 49 as an example, only 11.4% of people were fully vaccinated on August 1, and on September 30, one and a half months later, this number quickly rose to 58.9%
5. Weather impact:
last The factor is the weather. This has not yet been confirmed, but some experts speculate that the decline in the epidemic in Japan is also related to temperature and rainfall. In the hot summer, people have fewer outdoor activities and mostly stay in air-conditioned rooms. This reduces the chance of indoor contact leading to shipwrecks. More.
However, it is still unclear how much role each of the above factors played in the decline of the epidemic. This requires further research.
Delta virus will still come back? Japan's next wave of peaks may be in mid-February next year, and China must also prevent a new wave of infections in winter and spring.
Overall, the decline in the epidemic in Japan is mainly due to a combination of recent large-scale vaccination and NPI measures. However, as the protective power of vaccines decreases over time and various social control measures are relaxed, a new wave of epidemic peaks may still arrive. According to calculations by researchers at the University of Tokyo, the next peak in Japan may be mid-February next year.
An example that can be used as a reference here is Israel.
Israel used to have the highest vaccination rate in the world. With rapid vaccination, the epidemic curve was quickly flattened. The number of new daily cases dropped from the highest of 11,000 daily cases in February to double digits. And it lasted for several months.
However, as social prevention and control measures were relaxed and vaccine protection declined, the epidemic in Israel resurfaced at the end of June, and soared to 22,000 cases per day on September 8. While this new wave subsided, it is still Thanks to booster shots in Israel.
According to a real-world protection study of more than 1 million people published by the Israeli Ministry of Health in the Lancet magazine, these people received the second dose more than 5 months ago. After the third dose, the vaccine’s protection against symptomatic infection reached 91%, and the protection against severe disease reached 92%.
Therefore, although Japan is currently controlling the epidemic very well, it may still face greater pressure for prevention and control in the future. This situation is not only faced by Japan, but also by our country.
On the first day of November, there were nearly 500 new infections across the country. As winter approaches, we still have huge pressure on prevention and control. In addition, many people have already received two doses of the vaccine very early, and currently their bodies The antibodies have dropped to a large extent and may not be enough to effectively protect Delta, which is very transmissible.
The vaccination rate is one aspect, and the actual protection brought by the vaccine is another equally important aspect. Therefore, it is increasingly necessary to strengthen vaccination for high-risk groups (such as the elderly, people with immune deficiencies, medical personnel, etc.) and people who have been vaccinated for more than 6 months. At the same time, as the season of high incidence of respiratory infectious diseases approaches, it is equally important to continue to strictly implement personal protective measures.
The prevention and control experiences and lessons of various countries, as well as the research on vaccines and epidemics, are all based on each other's reference. We can learn from each other's strengths, respect science, and dynamically adjust epidemic prevention strategies. This is the most important thing we have learned from this epidemic.
