Reporter/Li Pengliang
Editor/Lu Yi
After four months of raging abroad, the new coronavirus the Omicron variant BA.5 finally broke through China’s defense lines and quickly invaded major cities.
Since community transmission of BA.5.2 was first detected in Xi'an on July 5, it has only taken 8 days to find local cases of BA.5 in seven cities including Xi'an, Beijing, Qingdao , Dalian , Tianjin, Shanghai, and Zhuhai. , mostly related to overseas import, and its import speed is nerve-wracking.
What is even more worrying is that in Zhuhai, Guangdong, where BA.5 is most severely spread, 76 cases of infection were discovered in just 4 days since the first case of infection was discovered on July 11. In Xi'an, which was the first to report the relevant epidemic, although the epidemic is now under control, 40 people were infected during the period, and the first community spread of this strain in the mainland occurred.
The ninth edition of the "Diagnosis and Treatment Plan for Novel Coronavirus Pneumonia" was released. What challenges will the invasion of BA.5 pose to my country's epidemic prevention and control? How should we respond to the ever-mutating viruses?
Some netizens uploaded photos of the scene of a blockade of a building in Zhuhai (picture source network)
html Most of the epidemics in 77 cities are imported from abroad, and experts predict that BA.5 will become the mainstream strain in ChinaRecently, BA.5 has been reported in almost one city a day. Break through the defense line quickly and import it into the mainland from abroad.
html On July 5, Xi'an first reported 10 positive infections, all of which were infected with the Omicron BA.5.2 branch. They are highly related to the local renewable resources trading and distribution market, and most of them are waste recycling personnel. This is the first time community transmission of this strain has occurred in mainland China. Fortunately, the epidemic has not spread further, and there are no new cases as of the 12th. Although the source of this epidemic is unknown, the virus came from abroad. html On July 6, Beijing also reported that three infected people were infected with the BA.5.2 branch of the Omicron variant strain, and the infected people had low sequence homology with existing and past local cases in Beijing and imported cases from overseas in the city. Different transmission chains. Based on the results of the epidemic survey and , it is initially considered to be a local cluster epidemic caused by imported cases.On July 7, The director of Dalian Center for Disease Control and Prevention stated that among the local people who were released from centralized quarantine after arriving from other places on July 3, an asymptomatic infection was found , and the virus gene sequence was Omikeron BA.5. The mutant strain is the first to be discovered in Dalian.
html On July 8, the Tianjin Center for Disease Control and Prevention stated in a media interview that the recent positive infections in Tianjin are all related cases imported from abroad. The sequencing results are all Omicron mutants, but they belong to different evolutionary branches. The local foreign epidemic prevention and control The input pressure continues to increase, making prevention and control difficult. Among them, the cases associated with the customs closure managers on June 26 were the BA.5.2.1 clade of the Omicron variant.On July 10, Shanghai reported that a community-wide infection was reported in Pudong New Area on July 8. The virus he was infected with was the Omicron BA.5.2.1 variant, and he was an overseas entry-related infection.
html On July 11, Qingdao reported at a press conference on the epidemic that the cases confirmed that day were staff members of the closed-loop management of the isolation hotel for immigrants. The gene sequencing results showed that it was the new coronavirus Omicron variant strain BA.5.2.1, and it was highly homologous with the new coronavirus gene sequencing results of the imported overseas cases confirmed in the quarantine hotel on July 7. html On July 13, Zhuhai also reported its first local case of BA.5.1 infection. The case was a local kindergarten teacher. She developed fever, muscle aches, cough, headache and other symptoms on the 11th and was diagnosed after seeking medical treatment. As of 12:00 on July 14, a total of 67 positive cases were found locally, all in the same transmission chain, and the virus strain belongs to the Omicron BA.5.1 clade. Since then, the number of cases has continued to rise, with 76 people infected so far.However, Zhuhai City has not announced the traceability results yet. It is only known that the activity trajectory of the first case is mainly in kindergartens and local shops, and there are no overseas records.
So far, in 8 days, 7 mainland cities have reported the discovery of local cases of Omicron BA.5. It is worth noting that, except for Zhuhai, the sources of the epidemic in other cities are related to overseas imports, and the above-mentioned cities all have ports of entry or first points of entry, and there are cross-border personnel exchanges.
7 15 July, some places related to the new crown epidemic in Zhuhai
Virologist Jin Dongyan of the University of Hong Kong believes that due to immunity gaps and other reasons, it is necessary to strengthen the management of port cities, make the sentry system more sensitive, and conduct stricter monitoring of key groups. .
Prior to this, BA.5 had been widely popular around the world.
According to WHO statistics, since the variant was first discovered in South Africa in March this year, as of July 7, 89 countries and regions around the world have reported related cases, and the proportion of reported sequences has reached as high as 50%, and is still rising. trend. This means that BA.5 is gradually becoming the main epidemic strain. And with the epidemic of BA.5, the number of new cases every week around the world has increased for five consecutive weeks.
WHO’s weekly report on COVID-19 cases and global deaths (Source: WHO)
Currently, BA.5 has become the main prevalent strain in more than ten countries including South Africa, Portugal, the United Kingdom, Israel, and the United States. . Among them, the combined proportion of BA.4 and BA.5 in the United States has grown rapidly and currently exceeds 70%. In Canada, it is reported that the BA.5 strain is causing a rapid increase in the number of new crown cases in several areas of Ontario, and the number of cases in Quebec has also increased by more than 50%. According to statistics from the Public Health Agency of Canada, as of June 19, BA.5 accounted for 38.4% of all cases.
As BA.5 breaks through the overseas import defense line, virus expert Chang Rongshan believes that the spread of BA.5 in the country is on the rise and may cause more infections. He predicted that by July and August this year, the BA.5 variant will be found in other southern provinces except Tibet. By August and September, domestic cases may be dominated by this variant.
Transmissibility is increasing, but there is no need to demonize
Although the name Omicron BA.5 variant is still slightly unfamiliar to the public, information about its super transmissibility and stronger pathogenicity is constantly emerging. Circulated online. Some media even claimed that the basic infection number of of BA.5, R0, exceeded 18, which is equivalent to one person infecting 18 people, and called it the "worst variant."
But is BA.5 really so dangerous?
"Don't demonize BA.5." Jin Dongyan repeatedly emphasized that there is no scientific basis for calling BA.5 the "worst strain". It is not much different from the previous generation variants. The only difference is transmission. A little bit faster.
According to CNN reports, some experts say that BA.5 is the worst variant of the new coronavirus
Jin Dongyan pointed out that in South Africa, where the variant originated, the scale of the outbreak of infection when BA.5 was compared with the spread of BA.1 and BA.2 variants It has become smaller, which means it causes fewer infections than the latter. At the same time, infections actually cause less severe illness and death.
At the same time, there are also many objections in the academic community to the statement that the basic infection number R0 of BA.5 exceeds 18.
such as Zhou Yebin, Ph.D. of from the University of Alabama at Birmingham, wrote in "Intellectuals" that this statement comes from some foreign news reports and is deduced from the comparison of the transmission speed of Omicron sub-strains in some countries. However, R0 is related to the mode of transmission, the degree of contact between people and the length of the infectious period. It is generally estimated through complex mathematical models, and simple estimates are not accurate.
Jin Dongyan pointed out that BA.5 has been introduced to Hong Kong for two or three months, but it only accounts for 1% of all cases so far, which is enough to show that the spread ability of BA.5 is not that exaggerated. In addition, now we should not calculate the simple R0 value, but should calculate Rt or Re. Among them, R0 refers to the average number of others that one case infects in the absence of immune foundation and prevention and control measures. The latter two refer to the number of people a patient can infect within a certain period of time, taking into account realistic conditions such as population immunity and prevention and control measures.
Jin Dongyan pointed out that Hong Kong’s Rt value has remained at a few points for a long time, which means that one person only infects one or two people on average, so there is no need for overly strict epidemic prevention measures.
In fact, among the seven cities affected by BA.5, except for Zhuhai, all other cities achieved zero new cases within a week of the first case being discovered, and no large-scale transmission occurred.
For example, after Xi'an reported the epidemic on July 5, 438 people in the area where the epidemic originated were quarantined, more than 1,400 people in close and sub-close contact were put under control, and 1,890 related people who had intersections were classified and managed. At the same time, control measures such as not leaving the area were implemented for 11,736 people in relevant risk areas.
On the same day, Xi'an also announced that from 0:00 on July 6, temporary control measures will be implemented in some public places in the city, mainly suspending dine-in food in various public entertainment venues and restaurants for seven days.
However, Jin Dongyan believes that with a small number of cases, there is no need to implement such a strict epidemic prevention policy.
He pointed out that most cases are not so contagious, and exhausting close and sub-close contacts is a waste of epidemic prevention efforts. One feasible method is to use CT values to distinguish cases. CT values higher than 30 are almost non-infectious; CT values below 30, especially below 20, mean that the infectivity is particularly high and require strict control. The time when a case is highly contagious will only last for a day or two. Continuous nucleic acid testing and management of this period can get twice the result with half the effort.
Regarding the control measures for entertainment venues and restaurants, Jin Dongyan believes that it is necessary to keep pace with the times and find the key to influencing communication through scientific methods.
Hong Kong’s current requirements for restaurants are that their operations must be ventilated, with a minimum of 6 air changes per hour. As long as the regulations on adequate ventilation are strictly enforced, large-scale virus transmission has not occurred in Hong Kong. "Even if someone is infected, it will only be a few people, no more than 10 at most." He pointed out that any outbreak in a restaurant must be due to insufficient ventilation.
"The general trend of new coronavirus (mutations) now is that the speed of transmission is getting faster and faster, and the ability of immune evasion is stronger." Chang Rongshan judged that the pathogenicity of the virus will continue to decline. Although it is spreading more and more, it will not It means it will be more dangerous.
html A research paper published on the preprint platform medRxiv on June 28 showed that during the BA.4/5 epidemic, the real-world severe illness rate in South Africa was 1.6%, and the death rate was 1.9%. The data is no better than that of BA. 1 has improved. In terms ofmortality rate, since the new crown epidemic, the case fatality rates of the original strain, beta strain, delta strain , BA.1 variant strain, and BA.4/5 variant strain are 5.3%, 6.9%, 6.4%, respectively. 2.5%, 1.9%. There has been a clear downward trend since the Beta strain. Compared with the original strain, the BA.4/5 mutant strain has a significantly lower mortality rate by about 60%.
Vaccine is still a suitable anti-epidemic method in China.
BA.5 When it invaded 7 cities, it coincided with the implementation of the ninth version of the "New Coronavirus Pneumonia Diagnosis and Treatment Plan". Among them, the quarantine control time for incoming personnel was adjusted from "14 days of centralized isolation medical observation + 7 days of home health monitoring" to "7 days of centralized isolation medical observation + 3 days of home health monitoring." Therefore, some people are worried that the significant reduction in entry control time may make it easier for the BA.5 variant to be imported overseas and spread further in the mainland.
Jin Dongyan believes that there is no need to worry about danger, because "7+3" is enough to detect the vast majority of infected people. He pointed out that reducing prevention and control measures is currently a major trend, and countries around the world are relaxing prevention and control standards. Many countries, such as Switzerland, Australia, and Norway, have announced full opening up and canceled all epidemic prevention restrictions. The United States no longer imposes restrictions on access to public places, does not mandate the wearing of masks, and has no restrictions on various business and entertainment venues. In response to the resurgence of the BA.5 epidemic, it is only recommended that areas with more severe epidemics should wear masks in indoor places.
At present, Hong Kong’s quarantine policy is also to isolate for 7 days. We still hope to continue to reduce the number, and eventually hope to become home quarantine. "In the long run, a balance must be struck between epidemic prevention and social economy."
Recently, the new requirement to no longer conduct nucleic acid testing on low-risk imported non-cold chain items has also attracted widespread attention. Chang Rongshan believes that this is a good thing to reduce the cost of epidemic prevention. Many studies have shown that the probability of spreading COVID-19 through items is very small, which also suggests that many disinfection efforts are unnecessary. "After the new coronavirus is excreted from the body, it only survives in aerosol for a few hours and sticks to the surface of items. It will also lose all infectious activity within 24 hours at room temperature. "
Although some prevention and control policies have been adjusted, Jin Dongyan believes that we should still be vigilant and constantly prepared for new variants, but we must not over-demonize them scientifically.
On July 5, Xi'an announced the implementation of temporary control over some public places, which aroused public opinion. Later, the rumor was refuted that it was not a "city closure"
He believes that the prevention and control strategy of the new variant is not fundamentally different from the previous one, and the most important thing at present is still to promote the vaccine. Vaccination. He emphasized that elderly people over 60 years old must be vaccinated, especially those over 80 years old, who are the highest risk group. If the three-shot vaccination rate among the elderly can reach 90%, the entire community will become safer.
In addition to the elderly, children should also be vaccinated. Although the mortality rate of children infected with COVID-19 is the lowest among all age groups, the death of one child is too heavy. At the same time, children go to school and are prone to cluster infections. After returning home, they can easily infect their elders at home, causing serious illness or even death of the elderly. .
Some people believe that the emergence of new BA.5 variants may pose a challenge to existing vaccines and lead to immune escape. Jin Dongyan pointed out that most vaccines in the world are based on the original strain and are still effective based on real-world data.
He took Hong Kong as an example. The infection probability of unvaccinated people is about 30%. After receiving three doses of Sinovac vaccine and Fubitai vaccine, the infection probability is about 10% and 4% respectively. The chance of infection is still reduced.
In addition, vaccines are more effective in preventing severe disease and death. Among them, the mortality rate after infection in the unvaccinated group is 3%. After receiving three doses of the Sinovac vaccine, the mortality rate will drop to 0.06%, which is lower than influenza .
"There are fewer infections (cases) in the mainland and lack of natural immunity, so we need to pay more attention to vaccination." He said.
Jin Dongyan also suggested using more antigen tests, which is especially important in places where resources are scarce. Take Sixian County in Anhui Province, which was previously at the center of the epidemic, as an example. The local area does not have the conditions to implement nucleic acid testing for all employees. In fact, it relies on support from all sides. In this case, it is better to use antigen testing, which will be more convenient and faster. "Early diagnosis, Early isolation has always been a major policy."
Faced with the characteristics of BA.5's rapid spread and low pathogenicity, Chang Rongshan suggested that "good steel is used on the blade." He believes that now in the face of the new coronavirus, it is better to prevent pneumonia than to prevent positive cases. He called on people with symptoms to take the initiative to get tested, which would save much more cost than nucleic acid screening for all employees.
Regarding how to encourage people to take the initiative in testing, Chang Rongshan believes that people who actively check and those who passively check can be distinguished. Those who have symptoms and are diagnosed with COVID-19 will be treated free of charge; those who are screened for COVID-19 will be treated at their own expense. The masses are naturally motivated to take the initiative to inspect.
