Particularly dangerous infections

Particularly dangerous infections are a group of diseases that 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 death or helplessness in humans, animals or plants. Therefore, biological weapons can be used not only to kill humans, but also to cause economic damage by killing animals or crops.

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Epidemiology

The distinctive epidemiological features of biological weapons are availability, low cost, the presence of an incubation period, the possibility of protection from damage, simplicity and secrecy of production, ease of distribution, wide public resonance, and the availability of information.

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Reasons

Hundreds of pathogens are capable of causing infectious diseases, but only a few 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 high virulence and the ability to cause a wide range of clinical manifestations. For example, the Venezuelan swine encephalitis virus, which can cause disease in approximately 100% of infected people, can be used as a biological weapon, but the Japanese encephalitis virus, which in most cases leads to a subclinical course of infection, cannot. Depending on the purpose of use, biological weapons are distinguished with lethal and non-lethal effects. NATO has presented a list of 39 potential pathogens and toxins that can be used as biological weapons. In Russia, there is also a similar list called "especially dangerous pathogens". In addition, there is a scale according to which pathogens of especially dangerous infections are distinguished by the required dose for use in an aerosol, stability in the environment, contagiousness, severity of the infection, speed of diagnosis, possibility of prevention and treatment. The most relevant are the pathogens of smallpox, plague, anthrax and botulism.

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Pathogens of especially dangerous infections

Anthrax (black smallpox)

The causative agent of anthrax is Bacillus anthracis, a non-motile, gram-positive, spore-forming bacterium. It is highly stable and virulent for decades. It can be produced and stored for long periods of time. Spores can be prepared to be the ideal size (1-5 µm) to penetrate deep into the respiratory tract. The lethal dose of bacteria for half of those infected by inhalation is 8-10 thousand spores or more. This amount can enter the respiratory system with a single breath within the spore cloud. In acute infections, only live, encapsulated bacteria are found in the body.

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Smallpox

The virus belongs to the genus Orthopoxvirus and is a DNA virus measuring 0.25 µm in diameter.

Plague

The causative agent of plague is a non-motile gram-negative coccobacillus Yersinia pestis. When stained according to Gram, it has the appearance of a club as a result of bipolar staining. Compared to the causative agent of anthrax, it is less stable in the environment, but the lethal dose is significantly lower.

Availability

The causative agents of particularly dangerous infections can be easily obtained. Bacteria such as Clostridium botulinum can be isolated from soil and cultured with basic microbiological knowledge and skills. Anthrax and plague agents can be isolated from animals and environmental objects in endemic regions, from microbiological collections, from medical companies or laboratories engaged in legitimate scientific and diagnostic research.

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Incubation period

It can last from several hours (staphylococcal enterotoxin B) to several weeks (Q fever). This type of weapon is characterized by a gradual development of the effect, it is distributed in an aerosol form without sound, smell, color, and does not cause sensations.

Pathogenesis of especially dangerous infections

Anthrax

The infection is transmitted in three ways: by contact, food, and airborne. The capsule of these microorganisms contains polyglutamic acid, which reduces the phagocytic activity of macrophages. However, spores can be phagocytized by tissue macrophages, in which they are able to germinate. Bacteria multiply in the area of penetration and enter the regional lymph nodes via the lymphatic route. During growth, anthrax bacteria synthesize three proteins: edema factor, lethal factor, and protective antigen, the latter creating complexes with edema and lethal factors. These complexes are called edema and lethal toxins. The action of the edema factor is associated with local activation of adenylate cyclase and the occurrence of edema. The action of the lethal factor leads to the development of tissue necrosis.

When consuming undercooked meat, bacterial spores can enter the gastrointestinal tract and cause the corresponding form of the disease. The inhalation form occurs when spores enter through the respiratory tract and is considered the most attractive from the point of view of creating biological weapons.

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Smallpox

The pathogen enters the body in several ways. Aerosol infection occurs through direct contact with infected individuals. Contact infection occurs through direct contact of the mucous membranes of sick individuals with the mucous membranes of a healthy person. In this case, the virus is transmitted by infected mucous secretions or infected cells of desquamated epithelium. The risk of infection increases sharply with aerosol spread of the virus through sneezing and coughing. One patient can be a source of infection for 10-20 healthy individuals. The incubation period is from 7 to 17 days.

The virus penetrates through the mucous membrane of the respiratory tract and enters the regional lymphatic pathways. After replication, viremia occurs within 3-4 days, which is not accompanied by clinical manifestations due to the active clearance of viruses by the reticuloendothelial system. As a result of continued viral replication, a second wave of viremia occurs after a few days, the viruses enter the skin and other organs, and patients develop the first symptoms of the disease.

Plague

In the bubonic form of plague, bacteria from the infected area (insect bite) enter the lymphatic system, reach the lymph nodes, where they multiply. As a result, the lymph nodes enlarge and represent a bubo - a very tense and inflamed lymph node, limiting movement due to severe pain. Organ damage occurs as a result of hematogenous dissemination.

The pneumonic form of plague may occur as a complication resulting from secondary bacteremia or as an independent form developing through inhalation of infected particles. The incubation period ranges from several hours to 12 days.

Symptoms of especially dangerous infections

Anthrax

It occurs in the following clinical forms, depending on the route of penetration: cutaneous, gastrointestinal, pulmonary. The incubation period is from 1 to 6 days, in some cases reaching 43 days after infection (according to data obtained after the investigation of the disaster in Sverdlovsk). The reason for such a long incubation is unknown, but in an experiment, live spores were found in the lymph nodes of the mediastinum of primates during 100 days of observation. After the start of antibiotic treatment, clinical symptoms may disappear, but the remaining live spores in the lymph nodes can lead to a relapse of the infection. With inhalation infection, nonspecific symptoms occur in the form of fever, cough, weakness, chest pain. The condition worsens within 24-48 hours. The lymph nodes enlarge and swell, hemorrhages in their stroma, ruptures and bleeding often occur, the pathogens enter the mediastinum. After a short period of apparent well-being, the condition suddenly deteriorates sharply. Cyanosis, dyspnea, stridor and signs of respiratory failure occur. Pneumonia has no characteristic signs. Hemorrhagic pleurisy may develop. In the absence of adequate treatment, bacteremia and toxemia occur, secondary metastatic foci appear in the gastrointestinal tract and the membranes of the brain and spinal cord. Hemorrhagic meningitis is detected at autopsy in 50% of those who died from anthrax.

Smallpox

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

Plague

Bubonic form

Acute onset, high fever (up to 40 °C) with chills, enlarged lymph nodes are typical. Buboes (painful enlarged lymph nodes with pronounced edema, the skin above them is smooth and hyperemic) are formed. The femoral and inguinal lymph nodes are most often affected, less often the axillary and cervical ones. A purulent vesicle with local lymphangitis, sometimes a scab, can be found at the site of the bite. Impaired consciousness from disorientation to delirium is typical. During the second week, suppuration of the lymph nodes is possible. The cause of death is sepsis, which occurs on the 3rd-5th day of the disease.

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Primary pulmonary form

The incubation period lasts 2-3 days. Hyperthermia, chills, headache quickly develop, and a cough develops within 20-24 hours, initially with mucous sputum. Then streaks of blood may appear in the sputum, and the sputum may also acquire a bright red color (raspberry syrup). Characteristic lung damage occurs in the form of compaction, pleurisy usually does not develop. Without treatment, death occurs within 48 hours.

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

Diagnostics of especially dangerous infections

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Anthrax

The clinical picture of inhalation infection has no pathognomonic symptoms. Characteristic changes in chest X-ray images are mediastinal expansion (60%), infiltration (70%), and pleural effusion (80%). Bacteria and their toxins appear in the blood two days after infection. Leukocytosis develops immediately after the toxins appear in the blood.

Bacteria can be detected in blood by Gram staining. Microbiological examination of peripheral blood, CSF and pleural effusion is performed for diagnostic purposes. Gram staining of sputum is not performed, since microorganisms are usually not detected. Serological diagnostic methods are used for retrospective confirmation of the diagnosis. Immunofluorescence reactions and PCR can be used for rapid diagnostics.

In case of inhalation infection, spores can be detected in secretions from the oropharynx (within 24 hours) and in stool (within 24-72 hours).

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Smallpox

The diagnosis of the disease is based on the characteristic rash. Light microscopy of rash biopsies may reveal eosinophilic elements (Guarneri bodies). Electron microscopy reveals viruses, but they are difficult to distinguish from other viruses of the orthopoxvirus family. Virological testing or PCR is used to clarify the diagnosis.

Plague

Clinical diagnosis is made in the bubonic form based on the presence of portals of entry, characteristic buboes, signs of generalized inflammation, and high leukocytosis. In the pulmonary form, the presence of characteristic infiltration of the lung tissue during radiographic examination. The diagnosis is confirmed by isolating the pathogen from blood, sputum, and lymph node aspirate. Surgical biopsy can lead to dissemination of yersinia. Serological tests are available (complement fixation reaction, indirect hemagglutination, immunofluorescence).

Treatment of especially dangerous infections

Anthrax

Usually, the pathogen strains are sensitive to penicillin antibiotics, therefore, in endemic areas, for the cutaneous form of infection, a group of penicillins is used intramuscularly or intravenously at 2 million units every 2 hours or 4 million units every 4-6 hours. Due to the high probability of laboratory modification of strains in the event of a biological weapon attack, ciprofloxacin is usually used intravenously at 400 mg every 12 hours. In case of allergy to penicillin, tetracycline (doxycycline 100 mg orally every 12 hours) or erythromycin (500 mg intravenously every 6 hours) can be used.

Based on 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, tienam, clindamycin, clarithromycin). The same drugs are used to treat and prevent anthrax in children (in age-appropriate doses) and pregnant women. Antibiotics should be prescribed as early as possible and continued for up to 60 days. If the patient's condition improves with parenteral treatment, it is rational to switch to oral administration of drugs.

The use of cephalosporins and co-trimoxazole is not recommended.

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

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Naturalpap pox

Symptomatic treatment is usually given. There is some positive experience with the antiviral drug cidofovir in great apes.

Plague

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

How to prevent particularly dangerous infections?

Despite the relative availability of biological weapons, their mass production is still limited by the fact that they require living microorganisms and protein substances that are sensitive to environmental factors (drying, sunlight, heating).

Anthrax

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

Another means of prevention is vaccination with an absorbed vaccine. Experiments have shown that in primates, a combination of vaccination and antibiotic chemoprophylaxis was more effective than vaccination and chemoprophylaxis separately.

Smallpox

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

If a source of infection is detected, it is necessary to immediately vaccinate those around you. Special respirators capable of trapping viral particles are considered protection against aerosol infection. Isolation of sick people is considered an important measure

Plague

The main task of prevention is to control rodents, use repellents to destroy fleas. Vaccination is not recommended for those traveling to endemic regions (it does not protect against aerosol infection). In case of increased risk of disease, it is recommended to take doxycycline 100 mg or ciprofloxacin 500 mg every 12 hours during the entire period of contact.

Forecast of especially dangerous infections

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Anthrax

The cutaneous form of the disease occurs in 95% of cases; in the absence of treatment, the mortality rate for this form is about 20%. In the intestinal form, the mortality rate is significantly higher due to the complexity of diagnosis and delay in treatment. The inhalation form is considered fatal if treatment is not started before clinical signs appear.

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Smallpox

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

Plague

The mortality rate for bubonic plague without treatment reaches 60%, for pneumonic plague - 90%. With timely treatment, the mortality rate decreases to 5%.

Possibility of protection against defeat

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

Simplicity and stealth of production

The technology and equipment for the production of biological weapons are not significantly different from the production of beer, wine, antibiotics, vaccines. Ease of distribution.

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

According to UN estimates, using 50 kg of the drug in a city with a population of 500 thousand people, it is possible to create a 2 km wide strip of destruction with a number of people affected, depending on the pathogen, from 30 to 125 thousand people.

Wide public resonance

Smallpox, plague and anthrax are well-known diseases in history that cause panic and terror among civilians. The recent use of anthrax spores in the United States has once again reminded us of the potential dangers of biological weapons and has caused widespread public outcry and a sense of insecurity.

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Availability of information

Until recently, it was almost impossible to obtain information about the production of biological weapons. Now, thanks to the World Wide Web, it is possible to obtain detailed information about the production of biological weapons.

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Anthrax

Infection usually occurs during work involving animal hair, boiling bones, and tanning leather. At the beginning of the 20th century, about 500 cases of the disease were described per year, occurring in the form of a cutaneous form. In 2001, in the United States, as a result of the use of biological weapons for terrorist purposes, anthrax spores were sent in letter envelopes, and 11 people were inhaled. In 1979, an accident in Sverdlovsk resulted in the release of spores, which apparently killed 66 people and a large number of animals. The area affected by the wind extended for 4 km for people, and for 50 km for animals.

Smallpox

Outbreaks of the disease occur for unknown reasons. In 1970, an outbreak occurred in a hospital in Meschede, Germany, probably due to aerosol spread of viruses. In 1972, an imported case of infection occurred in Yugoslavia, 11 people were infected from a patient, and a total of 175 people fell ill.

Plague

There are three known plague pandemics. In the Middle Ages, the most severe (second) pandemic killed a third of the population of European countries. The last pandemic occurred in 1898. In 1994, an outbreak of pneumonic plague was noted in India. Several cases of bubonic plague are observed annually on the West Coast of the United States. Humans are not involved in the life cycle of plague pathogens. The disease usually occurs in regions with a large number of infected wild rodents (rats, mice, squirrels), which are a natural reservoir. Several cases of pneumonic plague infection have been described through close contact with infected cats. The disease can be transmitted from person to person.

The infection is transmitted to humans from rodents through the bite of infected fleas, and from person to person through airborne droplets through contact with a coughing patient with the pulmonary form of plague.