The latest online "China Centers for Disease Control and Prevention Weekly" disclosed on February 10 the super transmission incident that occurred in Tonghua City, Jilin Province in January 2021.
The super-spreader of the incident was a 44-year-old male lecturer. As of January 31, he had caused at least 141 related cases of infection, and most of the infected were elderly people who participated in health care products lectures.
The lecturer held three lectures, and the COVID-19 attack rate of the participants in the three lectures reached 90% (40 participants, 36 were infected), 90% (31 participants, 28 were infected) and 38% (26 participants) 10 people were infected).
The above details are disclosed in the paper "Outbreak Reports: COVID-19 Super Spreading Event Amongst Elderly Individuals—Jilin Province, China, January 2021". Units include China CDC, Jilin CDC, Zhejiang CDC, etc.
On January 10, 2021, four people returned to Jilin from Wangkui County, Suihua City, Heilongjiang Province.
Their nucleic acid test for the new coronavirus (COVID-19) was positive, and then the new crown epidemic broke out in Tonghua City, Jilin Province.
On January 11, Jilin Province launched an emergency plan for COVID-19 prevention and control.
The Chinese Center for Disease Control and Prevention and the Jilin Provincial Center for Disease Control and Prevention jointly conducted an epidemiological investigation and tracked the epidemic.
According to the survey results, starting from January 20th, Dongchang District of Tonghua City will be adjusted to a high-risk area, scientifically divided and precise prevention and control will be carried out to prevent the spread of the virus.
L in the paper is Lin, an individual marketer from Heilongjiang.
Previously, Zhang Yan, deputy director of the Jilin Provincial Health and Health Commission, said that Lin had traveled to and from Heilongjiang and Jilin provinces several times from January 6 to 11. 4 marketing activities for middle-aged and elderly people-1 in Gongzhuling City, with 38 participants; 3 in Tonghua City, with 107 participants, totaling 145 people.
According to Xinhua News Agency, Mr. L promotes linseed oil.
According to the situation learned by flow regulators and market supervisors, L's marketing and promotion in the two health centers are all linseed oil products.
The investigation found that the health care center called a large number of middle-aged and elderly people to "listen to classes" through the process of "street gift registration-build WeChat group-participate in activities and give eggs-1 person can bring gifts for more than one person to upgrade" to promote products.
Many elderly people accidentally get tricked for these free eggs.
L. A direct infection of 81 cases, at least 60 second- and third-generation cases
As of January 31, 2021, a total of 310 cases have been reported in Tonghua City, all from Dongchang District.
Among them, there are 290 patients with symptomatic new crowns and 20 patients with asymptomatic new crowns.
One person died and 51 people have been discharged from hospital.
The median age of the patients was 56 years (range 2 to 95 years); among them, 142 were males (45.81%) and 168 were females (54.19%).
As of January 31, 140 cases have been related to the same case (in this report, the case is called L), which indicates that L is a super spreader.
L is a 44-year-old man who travels frequently and is a lecturer in the promotion of certain health products.
From December 23, 2020 to January 3, 2021, L took a train and plane to Shandong, Shanxi, Henan and Heilongjiang.
From January 3 to 6, Mr. L arrived in Heilongjiang by train; on January 7, he entered Jilin Province by train and arrived in Changchun City.
From January 9th to 12th, L lived in Tonghua City, Jilin Province, and hosted a product promotion training course.
He eats in a small restaurant and is in contact with the outside world.
L took the K350 train on January 5 and sat next to 2 of the 4 confirmed cases in Wangkui County, Suihua City, Heilongjiang.
He arrived in Tonghua City, Jilin Province on January 9, and conducted 3 training sessions in the following 2 days.
At noon on January 10, due to muscle pain and other symptoms, L went to a pharmacy (when measured at the pharmacy, his body temperature was within the normal range).
From January 10th to 11th, Mr. L gave 3 lectures at location A in Tonghua City, and each lecture lasted about 2.5 hours.
The classroom at location A is about 30 square meters with closed doors and windows.
In these three lectures, L did not wear a mask.
A total of 97 participants (40, 31 and 26) participated in the 3 lectures.
Most participants are retirees.
Among them, 61% (59/97) are women; the median age is 72 years (60 to 87 years).
As of January 31, 76% (74/97) of the lecture participants tested positive for COVID-19.
The attack rates of the three classes were 90% (36/40), 90% (28/31) and 38% (10/26).
In addition, L has also infected at least 7 other contacts, including 5 employees at location A (Ms. D is in the same hotel as L, and the rooms are adjacent; Ms. E is an employee of L’s dining restaurant, and L is here. Eaten twice).
L's close contacts spread the virus during other lectures, shopping, and playing mahjong.
L's close contacts have infected more than 30 cases.
In short, until January 31, L had directly infected 81 cases (first-generation cases) in Dongchang District, Tonghua City, and indirectly infected at least 60 cases (second- and third-generation cases).
On January 10, the Jilin Provincial Center for Disease Control and Prevention sequenced the new coronavirus isolated from the first throat swab samples collected from Wangkui County, Suihua City, Heilongjiang Province.
On January 12, the sequencing data was sent to the Chinese Center for Disease Control and Prevention for whole-genome sequencing.
These 4 genome samples belong to the L genotype (b.1.1) of the European branch I, and there are 12 nucleotide mutations in the first case of the Dalian outbreak in December 2020 and the Wangkui outbreak in Suihua, Heilongjiang in January 2021.
On January 16, the Jilin Provincial Center for Disease Control and Prevention provided the second batch of 11 samples (including L’s sample) to the Chinese Center for Disease Control and Prevention for whole-genome sequencing analysis.
The sequences of these two batches are highly homologous and belong to the same transmission chain.
The 30-square-meter classroom is crowded with 30 people. Mr. L does not wear a mask during lectures
The epidemic in Tonghua City, Jilin Province was detected earlier, but developed rapidly.
The outbreak of the epidemic is directly related to L and has obvious intergenerational transmission.
Most of the cases in the outbreak are retired elderly people in small and medium-sized cities.
The joint epidemiological survey found that these people lived a certain type of settled life, had similar socioeconomic levels, and were eager to participate in external social activities.
They take free buses to other locations, which greatly expands the scope of activities for retired elderly people.
Due to the older age of course participants, the proportion of severe and critically ill outbreaks is high.
As of the end of January, 47 severe and critical cases have been reported, accounting for 15.2% of the total, of which one 87-year-old case died on January 25.
There are three main factors that led to this outbreak: First, Mr. L developed muscle pain and went to the pharmacy to buy medicine on January 10.
This indicates that L may be in the early stages of new crown infection when he held his speech on January 10 and January 11.
The early stages are considered the most contagious.
Secondly, most of the participants in his training seminars are elderly, with a median age of 72 years.
These lectures lasted a long time and were held in small confined spaces.
Third, the participants did not have personal protection measures and did not maintain social distancing.
The classroom is very crowded, there are about 30 people in a 30 square meter space.
L and many participants did not wear masks in class.
In addition, the epidemic is relatively controllable, and no new mutant strains have been found through whole-genome sequencing.
Therefore, this investigation shows that there is no evidence of increased virulence or transmission.
In winter, the life of retirees in the north is relatively static, and attending various lectures is an attractive activity.
Therefore, the imported new coronavirus can spread easily and widely.
Researchers recommend that local governments strengthen infection control management and reduce unnecessary large-scale indoor gatherings in winter, especially in northern China.
The researchers also suggested that health education for the elderly should be strengthened to promote the use of effective physical protection.
The Paper Journalist He Liping