Especially dangerous infections

Especially dangerous infections are a group of diseases, which include the following infections: plague, anthrax, smallpox, which can be used as biological weapons or for terrorist purposes.

Biological weapons are microorganisms or their toxins used to cause the death or helplessness of humans, animals or plants. Therefore, biological weapons can be used not only for human death, but also for causing economic damage from the death of animals or crops.

[1], [2], [3],

Epidemiology

Distinctive epidemiological features of biological weapons - accessibility, low cost, the existence of an incubation period, the possibility of protection from defeat, the simplicity and secrecy of production, ease of distribution, broad public resonance, the availability of information.

[4], [5], [6]

Causes

Hundreds of pathogens are capable of causing infectious diseases, but only some of them can be used as biological weapons. Many of them are pathogens of zoonotic infections, which are dangerous for both humans and animals. The most effective method of spreading infectious diseases is aerosol, as a result of which pathogens or toxins directly enter the lungs. However, in this case, the damaging agent must be stable in the form of an aerosol, have a high virulence and the ability to cause a wide range of clinical manifestations. For example, the Venezuelan porcine encephalitis virus, capable of causing a disease in about 100% of infected people, can be used as a biological weapon, and the Japanese encephalitis virus, which in most cases leads to a subclinical course of infection, does not. Depending on the purpose of the application, biological weapons with a lethal and non-lethal effect are singled out, NATO has provided a list of 39 potential pathogens and toxins that can be used as biological weapons. In Russia there is also a similar list, which is called "especially dangerous pathogens". In addition, there is a scale according to which the pathogens of particularly dangerous infections differ in the required dose for use in aerosol, stability in the environment, contagiousness, the severity of the infection, the speed of diagnosis, the possibility of prevention and treatment. The most relevant are the causative agents of smallpox, plague, anthrax and botulism.

[7], [8], [9],

The causative agents of especially dangerous infections

Anthrax ("smallpox")

The causative agent of anthrax is Bacillus anthracis, a fixed Gram-positive spore-forming bacterium. It has a high stability and virulence for decades. Can be produced and stored for a long period of time. Spores can be prepared in such a way that they correspond to an ideal size (1-5 microns) for entry into the deep airways. The lethal dose of bacteria for half of the affected by the inhalation route is 8-10 thousand spores and more. This amount can get into the respiratory system with one breath inside the cloud of spore distribution. In the case of an acute infection in the body, only live capsules covered with a capsule are found.

[10], [11], [12],

Smallpox

The virus belongs to the genus Orthopoxvirus, it is a DNA virus 0.25 μm in diameter.

Plague

Pathogen plague - motionless Gram-negative coccobacillus Yersinia pestis. When painting according to Gram, it looks like a mace as a result of bipolar staining. Compared with the causative agent of anthrax, it is less stable in the environment, but the lethal dose is much lower.

Availability

Pathogens of especially dangerous infections can be easily obtained. Such bacteria as Clostridium botulinum can be obtained from the soil and cultivated in the presence of elementary microbiological knowledge and skills. Pathogens of anthrax and plague can be isolated from animals and environmental objects in endemic regions, from microbiological collections, from medical companies or laboratories engaged in scientific and diagnostic development legally.

[13],

The incubation period

It can range from several hours (staphylococcal enterotoxin B) to several weeks (Ku-fever). This type of weapon is characterized by the gradual development of the effect, it spreads in aerosol form without sound, smell, color, does not cause sensations.

Pathogenesis of especially dangerous infections

Anthrax

Transmission of infection occurs in three ways, contact-household, food and airborne. In the capsule of these microorganisms there is polyglutamic acid, which reduces the phagocytic activity of macrophages. Nevertheless, spores can be phagocytosed by tissue macrophages, in which they are able to germinate. Bacteria reproduce in the area of penetration and enter the lymph nodes regional lymphogenically. Anthrax bacteria in the process of growth synthesize three proteins, edematous factor, lethal factor and protective antigen, the latter creates complexes with a swelling and lethal factor. These complexes are called edematous and lethal toxins. The action of the edematous factor is associated with local activation of adenylate cyclase and the appearance of edema. The action of the lethal factor leads to the development of tissue necrosis.

When consuming meat that has suffered a lack of heat treatment, bacterial spores can enter the digestive tract and cause an appropriate form of the disease. Inhalation form occurs when the spores come through the respiratory tract and is considered the most attractive in terms of creating biological weapons.

[14], [15], [16], [17],

Smallpox

The causative agent penetrates into the body in several ways. Aerosol infection occurs by direct contact with infected individuals. Contact pathway of infection occurs when direct contact of mucous diseased with mucous membranes of a healthy person. In this case, the virus is transferred by the infected secret of the mucosa or infected cells of the desquamated epithelium. The risk of infection increases dramatically with the aerosol spread of the virus during sneezing and coughing. One patient can be the source of infection for 10-20 healthy individuals. The incubation period is from 7 to 17 days.

The virus penetrates through the mucosa of the respiratory tract and enters the regional lymphatic pathways. After replication for 3-4 days, there is viremia, which is not accompanied by clinical manifestations due to active virus clearance by the reticuloendothelial system. As a result of the ongoing replication of viruses, a second wave of viremia develops in a few days, viruses enter the skin and other organs, the patients have the first symptoms of the disease.

Plague

When the bubonic form of the plague, the bacteria from the infected area (insect bite) enter the lymphatic system, reach the lymph nodes where they multiply. As a result, the lymph nodes increase and represent a bubo of a very tight and inflamed lymph node that restricts movement due to severe pain. The defeat of organs occurs as a result of hematogenous dissemination.

The pulmonary form of the plague may occur as a complication as a result of secondary bacteremia or in the form of an independent form that develops by inhalation of infected particles. The incubation period ranges from several hours to 12 days.

Symptoms of especially dangerous infections

Anthrax

Flows in the following clinical forms, depending on the pathway of penetration of cutaneous, gastrointestinal, pulmonary. The incubation period is from 1 to 6 days, in some cases reaches 43 days after infection (according to data obtained after the Sverdlovsk disaster investigation). The reason for such a prolonged incubation is unknown, but in an experiment in the mediastinal lymph nodes in primates, live spores were detected during 100 days of observation. After the initiation of antibiotic treatment, clinical symptoms may disappear, but the remaining live spores in the lymph nodes can lead to relapse of the infection. With the inhalation route of infection, there are nonspecific symptoms in the form of fever, cough, weakness, pain in the chest. The condition worsens within 24-48 hours. Lymph nodes increase and swell, hemorrhages often occur in their stroma, ruptures and bleeding, pathogens get into the mediastinum. After a short period of visible well-being, suddenly the condition deteriorates sharply. There is cyanosis, dyspnoea, stridor and signs of respiratory failure. Pneumonia does not have the characteristic signs. It can develop hemorrhagic pleurisy. In the absence of adequate treatment, bacteremia and toxemia occur, secondary metastases in the gastrointestinal tract and the membranes of the brain and spinal cord occur. Hemorrhagic meningitis is detected on autopsy in 50% of the deaths from anthrax.

Smallpox

The first symptoms of the disease are fever, headache, muscle pain, vomiting. The main symptom is a rash that first appears on the face and distal parts of the limbs, then spreads to the trunk. The greatest number of elements is observed on the face and extremities. First the rash resembles measles. However, in most cases with measles, the rash is located mainly on the trunk, there are elements of the rash at different stages of development, after the rash the patient quickly becomes infectious. At smallpox, the patient remains infectious until all the elements of the rash disappear. Clinical variants of the course of infection are diverse from low-symptom to lethal, haemorrhagic forms. Complications of the disease - encephalitis, ARDS, blindness.

Plague

Bubonic form

Characteristic of acute onset, high fever (up to 40 ° C) with chills, enlarged lymph nodes. Bubbons are formed (painful enlarged lymph nodes with pronounced edema, the skin above them is smooth hyperemic). Femoral and inguinal lymph nodes are more often affected, more rarely - axillary and cervical. At the site of the bite, you can find a purulent vesicle with local lymphangitis, sometimes a scab. Characterized by a violation of consciousness from disorientation to delirium. During the second week, suppuration of the lymph nodes is possible. The cause of deaths is sepsis, which occurs on the 3-5th day of the disease.

[18], [19], [20],

Primary pulmonary form

The incubation period lasts 2-3 days. Quickly there is a hyperthermia, a fever, a headache, within 20-24 h develops a cough, at first with a mucous sputum. Then blood streaks may appear in the sputum, and sputum may acquire a bright red color (crimson syrup). There is a characteristic lesion of the lungs in the form of densification, pleurisy usually does not develop. Without treatment, death occurs within 48 hours.

Other forms of the plague are septic, meningitis, pharyngeal, benign (in endemic regions).

Diagnostics of especially dangerous infections

[21], [22], [23], [24]

Anthrax

The clinical picture of the inhalation route of infection has no pathognomonic symptoms. Characteristic changes in chest radiographs are an enlargement of the mediastinum (60%), infiltration (70%), pleural effusion (80%). Bacteria and their toxins appear in the blood two days after infection. Leukocytosis develops immediately after the appearance of toxins in the blood.

Bacteria can be found in the blood after Gram staining. For diagnostic purposes, microbiological examination of peripheral blood, CSF and pleural effusion is carried out. Gram stain is not sputumed, as microorganisms are usually not detected. Serological diagnostic methods are used for retrospective confirmation of the diagnosis. For rapid diagnosis, immunofluorescence and PCR reactions can be used.

In case of inhalation, spores can be found in the separated oropharynx (within 24 hours) and in the stool (within 24-72 hours).

[25]

Smallpox

The diagnosis of the disease is based on a characteristic rash. When light microscopy biopsies of the rash, one can detect eosinophilic elements (corpuscle Guarneri). In electron microscopy, viruses are detected, but they are difficult to distinguish from other viruses of the orthopoxvirus family. To clarify the diagnosis, a virological study or PCR is used.

Plague

Clinical diagnosis is made in the bubonic form on the basis of the presence of entrance gates, characteristic buboes, the presence of signs of generalized inflammation, high leukocytosis. With pulmonary form - the presence of a characteristic infiltration of lung tissue during radiographic examination. The diagnosis is confirmed by the excretion of the pathogen from the blood, sputum, aspirate of the lymph nodes. Surgical biopsy can lead to dissemination of yersinia. There are serological tests (complement fixation, indirect hemagglutination, immunofluorescence).

Treatment of especially dangerous infections

Anthrax

Usually strains of the pathogen are sensitive to the antibiotics of the penicillin series, therefore in the endemic zones with the cutaneous form of infection a group of penicillins is administered intramuscularly or intravenously for 2 million units in 2 hours or 4 million units in 4-6 hours. Because of the high probability of laboratory modification of strains in the case attacks by biological weapons usually use ciprofloxacin intravenously 400 mg after 12 hours. When allergic to penicillin can be used tetracycline (doxycycline 100 mg at 12 hours inside) or erythromycin (500 mg intravenously after 6 hours).

Based on the new data (2001), the recommendations were slightly modified. Treatment should be started with ciprofloxacin or doxycycline (in the above doses) in combination with one or two other antibiotics (rifampicin, vancomycin, penicillin, ampicillin, chloramphenicol, thienam, clindamycin, clarithromycin). These same drugs are used to treat and prevent anthrax in children (in age doses) and pregnant women. Antibiotics should be prescribed as soon as possible and continue treatment for up to 60 days. With the improvement of patients' condition against the background of parenteral treatment, it is rational to switch to taking medications inside.

It is not recommended to use cephalosporins and co-trimoxazole.

For the purpose of pathogenetic therapy, it is recommended to use infusion therapy, vasoactive drugs - in case of development of shock, respiratory support - in case of hypoxemia.

[26]

Naturalpoppox

Usually, symptomatic treatment is performed. There is little positive experience with the use of the antiviral drug sidofovir in the anthropoid apes.

Plague

Treatment should be started immediately. In septic and pulmonary form, treatment should be started within the first 24 hours. It is recommended that streptomycin is administered at a dose of 1 g every 12 hours intramuscularly for 10 days. Gentamicin in a dose of 5 mg / kg intramuscularly or intravenously once a day or 2 mg / kg for the first administration, then at 1.7 mg / kg intramuscularly or intravenously every 8 hours. The alternative drug is doxycycline at a dose of 100 mg intravenously twice a day day, ciprofloxacin 400 mg intravenously every 12 hours or chloramphenicol (levomycetin) at 25 mg / kg intravenously every 6 hours. In meningeal form, chloramphenicol is considered the drug of choice because of its high penetration into the subarachnoid space. Beta-lactam antibiotics for the treatment of plague do not apply.

How to prevent especially dangerous infections?

Despite the relative availability of biological weapons, mass production is still limited by the fact that it requires live microorganisms, protein substances that are sensitive to environmental factors (drying, sunlight, heat).

Anthrax

The main preventive measures are anti-epidemic control in livestock-breeding farms, vaccination of animals, veterinarians, textile workers (wool-related) enterprises, introduction of restrictions on the use of wool in industry and everyday life. In the case of suspected contact with the goal of chemoprophylaxis, ciprofloxacin is used. Alternative drugs - doxycycline and amoxicillin. Based on practical experience, experts from the United States recommend that prophylaxis with ciprofloxacin be performed within 60 days after probable contact.

Another means of prevention is vaccination with an absorbed vaccine. It has been shown experimentally that in primates the combination of vaccination and chemo-prophylaxis with an antibiotic was more effective than vaccination and chemoprophylaxis alone.

Smallpox

The main type of prevention is vaccination. However, due to the lack of spontaneous morbidity since the mid-1970s, vaccination against smallpox has been excluded from the vaccination calendar.

When identifying the focus of infection, it is necessary to urgently vaccinate others. Protection from aerosol contamination is considered to be special respirators capable of delaying viral particles. An important measure is the isolation of the sick

Plague

The main goal of prevention is the fight against rodents, the use of repellents to kill fleas. When leaving for endemic regions, vaccination is not recommended (does not protect against aerosol infection). In case of an increased risk of the disease, it is recommended to take 100 mg of doxycycline or 500 mg of ciprofloxacin every 12 hours during the entire contact time.

Forecast of especially dangerous infections

[27], [28],

Anthrax

The cutaneous form of the disease occurs in 95% of cases, in the absence of treatment, the lethality with this form is about 20%. With intestinal form, lethality is significantly higher due to the complexity of diagnosis and treatment delay. Inhalation form is considered fatal if the treatment is not started before the appearance of clinical signs.

[29]

Smallpox

When used as a biological weapon, lethality in unvaccinated individuals is 20-40%.

Plague

Mortality in the bubonic plague without treatment reaches 60%, with pulmonary plague - 90%. With timely treatment, mortality is reduced to 5%.

The possibility of protection from defeat

Persons who distribute biological weapons in aerosol form must have resistance to the disease, which is achieved by vaccination or preventive use of medicines. Unlike chemical weapons, pathogens of especially dangerous infections are usually unable to penetrate the body through intact skin.

Simplicity and secrecy of production

Technology and equipment for the production of biological weapons does not differ significantly from the production of beer, wine, antibiotics, vaccines. Ease of distribution.

Biological weapons can be easily distributed using agricultural irrigation devices, certain meteorological conditions, ventilation systems and much more.

According to the UN estimate, with the help of 50 kg of the drug in a city with a population of 500 thousand people, it is possible to create a 2 km wide strike zone and the number of affected, depending on the pathogen, from 30 to 125 thousand people.

A wide public response

Smallpox, plague and anthrax are widely known in the history of the disease, which cause panic and horror among the civilian population. The recent use of anthrax in the United States once again recalled the potential danger of biological weapons and caused a wide resonance and insecurity in society.

[30], [31],

Availability of information

Until recently, it was almost impossible to obtain information on the production of biological weapons. Now thanks to the worldwide computer network, you can get detailed information about the production of biological weapons.

[32], [33], [34],

anthrax

Usually, infection occurs when working with animal hair, digesting bones and dressing the skin. At the beginning of the XX century about 500 cases of diseases per year were described, which proceeded in the form of a cutaneous form. In 2001, in the US, as a result of the use of biological weapons for terrorist purposes, anthrax spores were sent in envelopes for letters, an inhalation contamination of 11 people occurred. In 1979, in Sverdlovsk as a result of the accident, a spewing occurred, which apparently killed 66 people and a large number of animals. In the wind, the affected area spread 4 km, and the animals - 50 km.

Smallpox

The occurrence of outbreaks occurs for unknown reasons. In 1970 in Germany in the hospital of the city of Meschede there was an outbreak, probably associated with the aerosol spread of viruses. In 1972 in Yugoslavia there was a case of imported infection from the patient infected 11 people, and only 175 people became ill.

Plague

Three pandemic plague are known. In the Middle Ages, as a result of the most severe (second) pandemic, one third of the population of European countries perished. The last pandemic originated in 1898. In 1994, an outbreak of pulmonary plague was noted in India. Several cases of bubonic plague are observed annually on the western coast of the United States. A person does not participate in the life cycle of plague pathogens. The disease usually occurs in regions with a large number of infected wild rodents (rats, mice, squirrels) that are a natural reservoir. Several cases of infection with the pulmonary plague are described in close contact with infected cats. The disease can be transmitted from person to person.

Infection is transmitted to a person from rodents when bitten by infected fleas, from person to person - by airborne droplets on contact with a coughing patient with a pulmonary form of plague.