Plague is no longer so terrible! Experts interpret its transmission characteristics and prevention methods.

　　Li dongzeng

　　editorial comment/note

　　Recently, a case of bubonic plague was confirmed in Wulate Zhongqi, Bayannaoer City, Inner Mongolia Autonomous Region. Subsequently, Inner Mongolia Autonomous Region announced that three plague foci had been discovered, and close contacts had been observed in isolation at home. This is the second case of plague in Inner Mongolia since last November. Because there have been many plagues in human history, many people turn pale at the sight of them. In fact, today, through effective preventive isolation measures and treatment, plague has long been less terrible. In this issue, we will introduce the spread characteristics and prevention methods of this disease in detail.

　　one

　　The infectivity of different plague is high or low.

　　There are three common types of plague, namely bubonic plague, pneumonic plague and septicemic plague. Plague is usually transmitted from animals to people through rat fleas biting the skin. After a rat flea carrying Yersinia pestis bites a person, Yersinia pestis invades the body from the skin and first reaches the nearest lymph node, causing inflammation of the lymph node, which leads to high fever and swollen lymph nodes. The swollen lymph nodes can be felt from pigeon eggs to the size of eggs, which is bubonic plague.

　　If patients with bubonic plague are not treated in time, swollen lymph nodes may fester and rupture. These pus are also contagious and may be infected if they are touched. Yersinia pestis may also spread to the blood and lungs, becoming septicemic plague and pneumonic plague.

　　Pneumonic plague developed from bubonic plague is called secondary pneumonic plague, and patients with pneumonic plague will have severe pneumonia. There is Yersinia pestis in the respiratory secretions of patients with pneumonic plague, which is highly contagious. Others will be infected after inhalation. People who inhale Yersinia pestis from the respiratory tract can directly suffer from pneumonic plague, which is called primary pneumonic plague. Whether it is primary pneumonic plague or secondary pneumonic plague, the manifestations are similar, and they all have the ability of respiratory transmission. Plague spread from person to person is mainly pneumonic plague.

　　Bubonic plague is the most common, but the risk is lower than pneumonic plague, and it is generally not contagious. However, patients with pneumonic plague are highly contagious, and the mortality rate is relatively high if they are not treated in time.

　　When Yersinia pestis spreads into the blood from lymph nodes or lungs, it may become septicemic plague. Septic plague is rare, but it is the most dangerous and has a high mortality rate. If the patient is not rescued in time, he may die within 1 to 3 days after onset. Septic plague appears ecchymosis because of bleeding under the skin, and the skin is purple-black. Therefore, it was called "Black Death" after the outbreak of plague in medieval Europe.

　　2

　　There is little chance of infection without entering the epidemic focus.

　　The main sources of infection of plague are rats and other rodents, and in China, it is mainly Rattus and Marmota. Other animals such as rabbits, foxes, wolves, camels and some domestic animals such as cats, dogs and sheep can also become sources of infection. The spread of plague among animals is mainly due to being bitten by rats and fleas.

　　Plague itself is spread among animals. There are 12 types of plague natural foci in China, distributed in 19 provinces, and animals in these natural foci may carry Yersinia pestis. Under normal circumstances, plague will not infect humans, but some people are at risk of being infected because of their professional needs or because of travel and exploration. Therefore, the staff in pastoral areas are often high-risk people infected with plague. People who enter pastoral areas are most likely to be bitten by rat fleas in the lower limbs, so the most common symptom of bubonic plague is swelling and pain of inguinal lymph nodes. There are also some people who enter the plague natural focus because of hunting or traveling, and they are also at risk of infection after contacting animals. If you strip animals suffering from plague, you may be infected by rat flea bites, or you may be infected by skin wounds touching the blood and body fluids of sick animals. Plague infected by stripping animals is more common in axillary and cervical lymph nodes of upper limbs.

　　If ordinary people do not enter the natural focus of plague, there is little chance of being infected with plague, and rats in urban areas usually do not carry Yersinia pestis. If you plan to travel to the plague natural focus, you must know the local plague situation in advance, try to keep a distance from wild animals, and don’t get in touch with the woodchuck when you see it. When entering the grassland, try to wear long trousers and gloves, avoid being bitten by rats and fleas, don’t sit and roll on the grassland, don’t picnic and camp on the grassland, and try to reduce the risk of infection.

　　three

　　Symptoms and treatment after plague infection

　　People infected with plague have different symptoms according to different types. The common characteristics of plague patients are rapid onset, repeated high fever, chills, shortness of breath, rapid heartbeat and severe headache. The symptoms of bubonic plague are mainly swelling and pain of lymph nodes, mainly groin, armpit and neck, which are generally unilateral swelling and pain. Patients dare not move easily when the pain is severe. The bubonic plague may be misdiagnosed as other causes of lymph node swelling and pain, such as acute lymphadenitis, lymphadenopathy caused by filariasis, tuberculosis of lymph nodes, etc., but other diseases with lymphadenopathy usually start slowly and develop less rapidly than bubonic plague.

　　Pneumonic plague is characterized by severe chest pain, cough, expectoration, hemoptysis, dyspnea and wheezing. Pneumonic plague is easily misdiagnosed as common bacterial pneumonia or viral pneumonia, so it needs to be distinguished from other pulmonary infection diseases, including lobar pneumonia, pneumonia secondary to influenza, novel coronavirus and so on.

　　Septic plague can be characterized by high fever, no increase in body temperature, unconsciousness, confusion and even coma, extensive bleeding, ecchymosis, cyanosis and necrosis of the skin, and some patients’ bodies are purple and black after death. Septic plague is easily misdiagnosed as coma and shock caused by other reasons, such as hemorrhagic fever with renal syndrome, septicemia caused by epidemic cerebrospinal meningitis, epidemic Japanese encephalitis spread by mosquito bites, shock caused by staphylococcus aureus or streptococcus infection, etc.

　　After people are infected with plague, the disease can be effectively controlled through timely drug treatment. At present, the treatment of plague is mainly antibacterial treatment, supplemented by symptomatic support treatment. Antibacterial treatment refers to the use of antibiotics to sterilize. Streptomycin is the most effective antibiotic against Yersinia pestis, especially in the treatment of pneumonic plague, mainly by intramuscular injection, which can be injected continuously for 10 days. Gentamicin can also be used in the case of human infection with plague. Tetracycline has bacteriostatic effect, which is effective for mild patients. It can be taken orally or used together with other antibiotics. Sulfonamides are widely used in the treatment and prevention of plague. Sulfonamides are the earliest synthetic antibacterial drugs, which have good curative effect on plague, and they are easy to use, stable in nature and low in price. Symptomatic support therapy refers to helping patients recover as soon as possible by means of antipyretic analgesia, anti-shock, respiratory support and nutritional support.

　　four

　　What should I do if I find a mouse at home?

　　Domestic hamsters and rabbits usually don’t have access to wild animals, and animals don’t naturally carry infectious diseases. Without the source of infection, they won’t be infected, so there is no need to worry about domestic hamsters and rabbits catching plague. However, rats, rabbits and other animals do have a lot of bacteria in their mouths. After being bitten, it is necessary to disinfect the wound in time to avoid bacterial infection. If the wound shows signs of infection such as redness, swelling, pain and skin color change, you need to seek medical attention in time.

　　Families find that rats need to be scientifically killed. The first is to clean up the dead corners and garbage in time to reduce the living space of rats. Secondly, try to block all the passages that mice may enter and leave the room, such as air-conditioning pipe holes and sewer holes, so that mice have nowhere to hide and can’t enter the room. Around houses, corridors and other areas, compliant rat traps, rat boards and rat poison can be placed in places where rats are infested, and eye-catching signs should be made at the same time to prevent others, especially children, from accidentally contacting rat poison.

　　Don’t put snacks in the house at will. The food and all kinds of food in the house should be stored out of the reach of mice. If conditions permit, community managers should invite professional rodent control companies to carry out rodent control in a unified way to improve efficiency. If you find dead rats at home, don’t touch them with your bare hands to avoid being bitten by rats and fleas. You can wear long trousers, masks and gloves, collect the dead rats in sealed plastic bags, and contact the community property management department to dispose of the dead animals.

　　Plague prevention includes bubonic plague prevention and pneumonic plague prevention. The bubonic plague is mainly caused by the bites of rats and fleas on animals, so the prevention of bubonic plague by ordinary people is mainly to avoid contact with animals in the natural focus of plague, and to prevent rats and fleas. If you must enter the epidemic area, you can wear long trousers, boots and gloves, and try not to expose your skin to avoid being bitten by rats and fleas.

　　During the tour, everyone should try not to touch wild animals, including wild animal carcasses. Don’t buy wild animals. If you find dead animals on the roadside, you should report them to the local health and disease control departments in time.

　　If you are just traveling, you can do these preventive measures well, and you don’t need to use drugs in advance to prevent it. If you are bitten by rat fleas in areas with plague, or have close contact with patients with pneumonic plague without protection, you can use tetracycline, doxycycline, sulfanilamide and other drugs to prevent it. (Author: Deputy Chief Physician, Department 2, Infection Center, Beijing You ‘an Hospital)