Producer: Popular Science China
Producer: Chen Anguo (Institute of Subtropical Agroecology, Chinese Academy of Sciences)
Producer: Computer Network Information Center, Chinese Academy of Sciences
On the evening of November 12, an official report from the Chaoyang District Health Commission of Beijing Municipality showed that on November 12, 2019, two people in Sunit Zuoqi, Xilingol League, Inner Mongolia Autonomous Region, were diagnosed as confirmed cases of pneumonic plague after expert consultation.
As soon as you see the word "plague", everyone may inevitably worry that many people have already worn masks. In fact, although the plague has caused great harm to human society, people in Beijing do not need to panic at present.
Because from the official notification, we can see three important pieces of information:
First, at present, the patient has been properly treated in relevant medical institutions in Chaoyang District, Beijing; second, relevant prevention and control measures have been implemented; third, Beijing has carried out inter-rat epidemic monitoring for many years, and no cases of Yersinia pestis have been found in rats.
For what is the plague, how to spread, in the official news everyone can see authoritative, comprehensive news, here I want to focus on answering the question asked by some friends "The plague has not yet become extinct?" By answering this question, I hope to let everyone understand that the plague can be said to be far and near to us, and there is no need to panic, but it cannot be taken lightly.
<h1>The plague was not eradicated</h1>
In the minds of many people, the plague, like smallpox, should have been eradicated long ago.
Not really. The plague did not go extinct. The possibility of contracting the plague has always been buried around us.
After the 1940s, the worldwide pandemic of plague did not occur again, but the epidemic on a smaller scale never stopped. Both inter-rat plague and human plague epidemics are characterized by irregular discontinuities and suddenness. In 1994, 30 years after the resting plague epidemic, there was another plague epidemic in Surat, India, with 876 cases and 54 deaths, causing 600,000 people to flee their homes and direct economic losses of more than US$ 1 billion.
According to WHO statistics from 1988 to 1997, 23 countries worldwide reported 25,467 cases of human plague, 1,813 deaths, and a case fatality rate of 7.12 percent [1].
Until now, there are still large areas of plague in China's northwest and southwest border provinces and neighboring countries, and from time to time, plague bacteria infect humans due to people camping in the wilderness and stripping marmots.
There are many natural foci around the world, and wild plague persists for a long time. Human plague is mostly transmitted from wild rats to domestic rats, and then transmitted to people by domestic rats. Unprotected personnel entering wild plague-affected areas during wilderness camping, inspection, construction, and military activities are most likely to be infected by the bites of diseased fleas; hunting in epidemic areas (catching marmots) will be directly affected by contact with the flesh and blood containing plague bacteria. Domestic plague is mostly transmitted from wild rats to domestic rats or the house rats themselves carry plague bacteria, and fleas on house mice can transmit plague to people after sucking blood containing plague and then bite people."
In short, the plague should not be taken lightly.
<h1>Go to these areas, see these animals, beware</h1>
You may think that plague is transmitted by domestic rats. Not really.
House mouse (Image: Veer Gallery)
The root cause of plague is in rats, the word for plague has the word "rat", people will think that the source of plague is in rats, in fact, it is more accurate to say that the source of plague is in rodent infected animals. Rodents are called rodentia in animal taxonomy, rodents that can infect and transmit plague, there are 186 species in the world, and there are more than 40 species in China. Rodents of wild rats are the basic reservoir and starting source of infection of Y. pestis, so they are called "rat-borne diseases" or "natural diseases of origin". Rodents naturally inhabit certain habitats, making plague mostly in the wild away from population strains, so plague is a "natural epidemic disease". Rodents and other rodents have different susceptibility and tolerance to plague bacteria, which can be divided into primary storage hosts and secondary storage hosts.
The main storage host can tolerate and preserve the plague bacteria for a long time, forming a natural source of plague, the most important of which are marmota and spermophilus. It refers to the genera marmot (Marmota) on the Qinghai-Tibet Plateau, the Volbita genus (Spermophilus) on the Songliao Plain, the Rhombomys (Rhombomys) in the Jungar Basin, the Sand Mariones (Meriones) and the Rattus in Yunnan on the Inner Mongolian Plateau.
The scientific name of the marmot is marmot.
Marmot emoji Image source: https://image.baidu.com
Marmots are similar in name to otters (carnivores) but far from systematic, and they are true to rats. Marmots are typical underground burrowing and herbivorous species, which will dig up a large amount of mud and pile it up to the ground, and eat a lot of pasture, which is a major harm to the grassland.
Marmot Mongolian is called "Tarbagan", Tibetan is called "Hala" and "Quwa", and The Han people are commonly known as "Snow Pig" and "Snow Cat". The body is thick and fat, weighing up to 5 to 8 kilograms, and the meat essence is delicious, which was previously hunted and eaten by herders and used for fur. It is the most stable reservoir of plague bacteria, with a high rate of bacteria, and it is easy to infect people during the process of peeling and picking meat. Therefore, try to avoid hunting and eating marmots, especially in endemic areas.
Marmota sibiricu Siberian marmot, distributed in Inner Mongolia, Russia and Mongolia (Image: Veer Gallery)
Is it safe not to hunt and eat groundhogs? Nor is it. The main storage host of plague bacteria is known to be at least 12 species in China, forming 1012 pieces of plague wild rat plague epidemic source area[1]
There are 14 species of marmots in the world, and 4 species in China, namely himalayan marmots, gray marmots (Altai marmots), long-tailed marmots (red marmots) and Siberian marmots (Mongolian marmots), which form plague foci in Qinghai-Tibet, Xinjiang and the Hulunbuir Plateau in Inner Mongolia, respectively.
Himalayan marmota himalayana (Photo quoted from Baidu Encyclopedia)
The genus mainly daur weasel, Alxa weasel and long-tailed weeds, forming plague fowl in the Songliao Plain, Ganning Loess Plateau, and Tianshan Mountains (the Tianshan plague source is formed by gray marmot-long-tailed weasels).
Daur weasel Spermophilus dauricus (photo quoted from Sogou image)
Others are the long-clawed gerbil, the Bu's voles and the Qinghai voles, which form plague foci on the Inner Mongolian Plateau, the Xilin Gol Plateau and northwest Sichuan, respectively, and the large velvet rat-Qi rat plague fowl in the mountains of northwest Yunnan.
Long-clawed gerbil meriones unguiculatus (Photo quoted from Sogou image)
Busch field mouse Lasiopodomys brandtii . (Photo quoted from Sogou image, photo by Andy Wong Research Group)
If domestic rats are infected with plague, most of themselves die easily. But they are associated with humans, but they also go to the wild, and once the domestic plague is endemic, they will be repeatedly alternated between rats and people. Its parasitic fleas bite people and form human plague. Among them, yellow-breasted rats, brown rats and black rats are important sources of human plague, and there have also been yellow-breasted plague foass in Yunnan and Guigui and the cradle of yellow-breasted rat-brown plague in the southeast coast. The source of yellow-breasted plague in Yunnan and Guigui and the yellow-breasted rat-brown plague in the southeast coast of China are such domestic plague epidemic sites.
<h1>New China has stopped the human plague epidemic, but the potential danger still exists</h1>
As we said earlier, the plague has not been eradicated, but in our country, the plague epidemic has ceased to occur.
According to incomplete statistics, in the more than 300 years before the founding of New China (1644-1949), there were six major plague epidemics in China, with a total of more than 2.59 million cases of plague and more than 2.39 million deaths in 501 counties (cities, banners) in 20 provinces (autonomous regions), and more than 1.155 million cases and more than 1.027 million deaths in the 50 years (1900-1949) of the first half of the 20th century alone.
After the founding of New China, the health work policy of focusing on prevention was implemented, and comprehensive prevention and control measures centered on the eradication of rats and fleas were adopted, and the human plague epidemic that had been raging for hundreds of years was basically controlled in only about 10 years. In the 50 years from 1950 to 1999, there were more than 79,000 cases of human plague and more than 27,000 deaths in China; of which the number of cases in the first 5 years accounted for 87.1% of the total number of cases, after which the human plague was further controlled, and there were only sporadic cases in The provinces and regions of Qinghai, Tibet, Yunnan, and Xinxin in the 1980s, with an annual incidence of only about 10 cases; but since the 1990s, the plague epidemic in China has shown a significant upward trend like the overall situation in the world, and the number of cases reported in the 10 years from 1990 to 1999 ( 371 cases) is 3.6 times higher than in the previous 10 years (102 cases), which is mainly related to the resurgence of yellow-breasted plague in Yunnan.
Nowadays, plague rats usually do not exist in most areas of China's interior, and the plains and urban areas in China are not the natural source of plague, and the public does not need to "talk about rat discoloration". However, the work of eliminating rat pests can still not be relaxed: First, rodents can carry a variety of pathogens, and there are more than 100 species of human-rat comorbid diseases known in the world, and there are 24 species in China, including 5 major categories of viral diseases, rickettsial disease, spirochetes, bacterial diseases and parasitic diseases. The most common current epidemics are hemorrhagic fever and leptospirosis, which can also threaten human health and life safety. Therefore, the density of the main pest rats must be monitored regularly to control them below the level of health hazards or economic hazards. Rats are also the most important hazards for crop and food storage.
Moreover, the natural source area of plague in China is still vast, the type is complex, the preservation mechanism of plague in nature is not very clear, its occurrence has the characteristics of discontinuity and suddenness, coupled with the development of modern transportation, with the development of economic development, frequent exchanges of personnel and materials, the danger of plague imported from abroad is also increasing. Therefore, the monitoring and prevention of plague must be carried out continuously!
<h1>Although the plague is "fierce," it is not uncontrollable</h1>
Although the plague is terrible, it is not irresistible and unpreparable. Plague bacteria are resistant to low temperatures, can survive at -30 ° C, can survive for months to years in frozen tissue or carcasses, and can survive for more than 1 year in pus, phlegm, fleas and soil. However, the resistance to the outside world is weak, not resistant to drying and heat, 100 °C can cause bacterial death after 1 minute, direct sunlight can only withstand 1 to 4 hours; the resistance to general disinfectants and fungicides is not strong, and it is sensitive to streptomycin, kanamycin and tetracycline.
In the second plague pandemic, the role of disinfection and isolation has been discovered, infectious disease prevention and control technologies have been created, and cremation has been advocated, achieving the "first sanitation revolution". This has led to a significant reduction in the number of deaths from the third pandemic. Plague gods are now hard to wreak havoc.
The terrible thing about the plague is its concealment and rapid development, and many patients die because they are too late to treat it. Therefore, the timely detection and diagnosis of the first patient is extremely important for the control and prevention of plague. Once a person is infected, if the diagnosis can be made quickly, most patients can be cured by early, combined, adequate, and sensitive antimicrobial treatment. Stable immunity is obtained after cure, and re-infection occurs rarely. The official notification also specifically pointed out that the patient has been properly treated, and relevant prevention and control measures have been implemented.
For severe infectious diseases such as plague, the emphasis should be on prevention. Travel should try to avoid entering potential plague-affected areas. When it is necessary to work in the epidemic area, it is necessary to strictly protect individuals and groups, and inject plague vaccine 1 to 2 months ago; if it is temporary to enter the epidemic area, long-acting sulfonamide or tetracycline should be taken orally. Tighten your trouser legs and don't sit and lie down next to animal caves in the wild. Individuals may be given mosquito-vector repellents to prevent flea bites. Before entering the camp, you must first exterminate the fleas and eliminate the rats, and repeatedly sweep to keep the station free of rats and fleas.
In China, there have still been sporadic cases of plague in recent decades, mostly due to the private hunting of wild animals such as marmots. Relevant departments in the epidemic areas should strengthen supervision, and publicize and educate the public to enhance ecological awareness, respect nature, fear wild animals, and coexist in harmony with nature.
Finally, I would like to stress once again that please do not spread false rumors or unconfirmed news, and the official notification shall prevail.
bibliography:
Zheng Zhimin, Jiang Zhikuan, Chen Anguo, editors-in-chief. Rodentology (2nd Edition)[M].Shanghai:Shanghai Jiao Tong University Press, 2012.