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Legionnaires' disease sounds a bit like the name in video games, but it is a real disease in real life. It is a systemic disease with pneumonia as the main manifestation caused by Legionella. It spreads through the air, and it will cause upper respiratory tract infection and fever after entering the human body from the respiratory tract, which can lead to respiratory failure and renal failure in severe cases. 1976 At the Legion Veterans Conference held in Philadelphia, USA in August, a disease suddenly prevailed among the participants. At that time, 22 1 person was sick, resulting in 34 deaths, so the disease was named Legionellosis, and the corresponding pathogen was also called Legionella.

Although the name is not so widely known, legionnaires' disease is indeed a common disease. The United States found the most cases, with an average of more than 20,000 cases per year. China first reported legionnaires' disease cases in Nanjing in 1982, and then all provinces and cities reported them. At present, there are sporadic cases and epidemic reports in dozens of countries on five continents. Many countries have listed legionnaires' disease as a national legal infectious disease and formulated a series of corresponding measures. China listed it as one of the new infectious diseases in 14, and the World Health Organization also included it in the report of infectious diseases.

Legionella is an aerobic Gram-negative bacterium, which is a common pathogen in life, just like Salmonella, Shigella, pathogenic Escherichia coli and Staphylococcus aureus. Legionella widely exists in natural fresh water environment and artificial water. At present, more than 50 species, 3 subgroups and 70 serotypes have been found. Among them, about 20 species can cause human pneumonia, and the most common is Legionella pneumophila (about 80% of all cases).

Legionella mainly invaded alveoli and bronchioles. When it invades the body, it first adheres to neutrophils and macrophages and is swallowed up. However, Legionella entering the cytoplasm can not be killed, but proliferates, leading to cell rupture, releasing intracellular enzymes and cytotoxic factors, and damaging lung tissue. In addition, Legionella can also produce and release a variety of toxins to cause persistent lung injury, and enter the blood stream to cause pathological changes in organs and tissues outside the lung.

The symptoms of legionnaires' disease are mainly divided into three categories: Legionella pneumonia is a kind of Legionella infection with pneumonia as the main clinical manifestation, and most patients belong to this category. Extrapulmonary syndrome refers to the spread of infection from the lung to other systems outside the lung, and Pontiac fever with acute fever as the main manifestation. Among them, Pontiac fever usually has mild symptoms, which can automatically stop and gradually recover after it develops to a certain extent without special treatment.

Although the mortality rate is not low, legionnaires' disease is not incurable. Macrolides or fluoroquinolones are the first choice for the treatment of Legionellosis, tetracycline and rifampicin are also effective, while penicillins, aminoglycosides and cephalosporins have no obvious effect on this disease. At the same time, maintaining the balance of water and electrolyte, using artificial respirator in respiratory failure, using vasoactive drugs in shock and dialysis in acute renal failure are all important treatment measures.

Moreover, Legionella usually does not spread from person to person, which is of course good news for human beings. Legionella usually exists in fresh water such as air conditioning cooling water and spreads in the form of water mist and aerosol. People get sick by breathing water mist from Legionella-contaminated water sources. As long as the environmental sanitation management is done well, there is no need to worry too much about the threat of Legionella.

How to control the prevalence of legionnaires' disease?

Usually, the spread of infectious diseases needs to meet the following three conditions at the same time: germs, transmission routes and susceptible people, and blocking the spread of diseases also starts from these three aspects. Legionnaires' disease is no exception. Controlling the spread of Legionella can kill Legionella, cut off the route of transmission and improve the autoimmune function.

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The viability of Legionella is not strong. Legionella is active in water at 20 ~ 45℃, and around 35℃ is the best growth temperature, so Legionella often breaks out in summer and autumn. Legionella can't survive in water above 60℃ for a long time, and they will die in just 3 minutes at 70℃.

Legionella is also easily killed by chlorine in water, so the risk of Legionella in fresh tap water is very low. Only when the water is stored in cooling towers, water tanks and other places for a long time, the chlorine has evaporated, and Legionella floating in the air can multiply in large quantities. For polluted water, adding appropriate chemical bactericide can kill Legionella.

In addition, ultraviolet sterilizer is also a common tool to kill Legionella, and adding ultrasonic wave can achieve better sterilization effect. The sterilization method of membrane filtration is also suitable for Legionella.

Transmission routing

In legionnaires' disease epidemic, people are usually infected in hospitals, office buildings, passenger ships and other buildings with dense personnel and central air conditioning system. Legionella propagates in artificial water and spreads in the form of water mist. In the outbreak of legionnaires' disease in new york, the pollution came from the air conditioning water cooling tower of the building. Investigators from the Health Department of new york inspected 22 buildings in the Bronx and found five water cooling towers from hospitals, shopping centers, office buildings and hotels. At present, new york has completed the disinfection of buildings infected with Legionella.

In order to prevent the breeding of Legionella, large buildings should regularly inspect and disinfect the central air conditioning system, cooling tower, fountain pool and other equipment to ensure the cleanliness of the water system. For ordinary people, air conditioners, water heaters and other equipment at home should also be disinfected regularly to maintain hygiene.

In addition, a 20 10 British study found that the probability of drivers suffering from Legionella is five times that of the general population. The research thinks that the reason is that the water in the windshield wiper water tank is not updated frequently, which has become a hotbed of Legionella. In 20 12 years, American researchers reached a similar conclusion. They found that Legionella can survive for a long time in car glass cleaning solution, and their number will continue to increase under the right temperature. When using the wiper, Legionella will be released with the spray, posing a potential threat to people. British researchers suggest that it is best to add cleaning products with antibacterial and bacteriostatic effects to the water tank.

susceptible population

At present, there is no ideal vaccine for legionnaires' disease, but improving autoimmune function is a very effective means to avoid the disease. After contact with Legionella, most people will not have symptoms, and a few people will get Legionella.

Legionnaires' disease can occur at any age, but most people are middle-aged men. The identified risk factors include smoking, alcoholism and immunosuppression (especially immunosuppression caused by corticosteroids).

Therefore, quitting smoking, regular life, proper exercise and paying attention to healthy diet can enhance physical fitness, and even contact with Legionella is not easy to be poisoned.