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According to the World Health Organization (WHO), cases of dengue fever were reported in only 9 countries before 1970. Currently, the number of states characterized by this disease has increased to 100. The most high level morbidity is observed in South America, South-East Asia and western part Pacific Ocean. But every day the virus is spreading more and more actively, causing outbreaks in new territories. The trouble is that the overwhelming majority of children suffer from severe forms of fever.

Dangerous tropical fever

Dengue fever is an acute viral disease - a transmissible zoonotic infection, accompanied by pyretic (over 39 ° C) temperature, severe intoxication, hypertonicity of muscle cells, joint pain, skin rash, and enlarged regional lymph nodes. It is most widespread in tropical and subtropical climates.

The disease has several synonyms: joint fever, bone crusher fever, five-day fever, tropical fever, date disease and giraffe fever.

The cause of tropical fever is an arbovirus that is resistant to high temperatures, which reproduces its own kind while inside the cell. It can exist in blood serum at room temperature for up to 2 months, and in a dried state for up to 5 years.

The causative agent of Dengue fever belongs to viruses of the family Togaviridae of the genus Flavivirus (arbovirus of antigenic group B)

Children are more often diagnosed with a severe form of the pathology, sometimes leading to death. In adults, in 70% of cases a mild course of the disease is observed.

For pregnant women, the danger is an increased risk of premature birth.

How to protect yourself from illness - video

Classification of the disease

There are two forms of fever:

1. Classical (bone breaking). Characterized by a mild course. It is observed in children of the local population and visitors of any age. It develops during the initial meeting of the body with the pathogen, that is, in the absence of immunity to the disease.
2. Hemorrhagic. It is characterized by the presence of pathology on the part of the blood coagulation system and an extremely severe course with a fatal outcome. This type of fever mainly affects children of two age groups: newborns and infants up to one year old with passive immunity, as well as children from two to three years old who have suffered the classic form of the disease.

Causes and factors of infection

The infectious yellow fever mosquito (Aedes aegypti) is the main vector of the virus. Its peculiarity is considered to be living mainly in urban conditions and eating in the morning and daytime, which contributes to the effective transmission of the pathogen. However, he is not the only reason diseases. The second most important is the Asian tiger mosquito (Aedes albopictus), which is well adapted to the cold climate of Europe.

Upon inspection you can see:

• enlarged peripheral lymph nodes;
• rash on the mucous membrane of the soft palate;
• white coating on the tongue;
• hepatomegaly (liver enlargement);
• skin rashes resembling urticaria (often pinpointed with nodules), ending with severe peeling after 7–9 days.

The rash is accompanied by severe itching, its appearance has a certain sequence:

• rib cage;
• inner surface of the shoulders;
• stomach;
• arms and legs.

The rash associated with dengue fever is accompanied by severe itching and leaves behind large areas of peeling

The average duration of classic dengue fever is 10 days.

Symptoms of hemorrhagic form in a child

A typical severe form of the disease has the following symptoms:

• pyretic body temperature (39–41 °C);
• hemorrhages under the skin;
• liver enlargement;
• vascular and cardiac (heart) failure.

The onset of the disease is sudden, accompanied by chills. Pain in muscles and joints is usually absent. Puffiness and redness of the face and body are observed. A pinpoint rash appears with the formation of papules, which is localized on the bend of the elbows and knees. After 5 days it spreads throughout the body, face and limbs. As the fever progresses, the person falls into a state of depression and apathy.

After 7–8 days, the disease subsides - the temperature drops, the skin gradually clears, and recovery begins.

In severe cases, the patient’s condition deteriorates sharply, a sign of which is:

• poor circulation in the form of pale and bluish skin;
• abdominal pain;
• increased heart rate and breathing;
• pinpoint hemorrhages on the skin of the forehead, legs, arms;
• bloody vomiting, loose black stools, indicating gastric bleeding;
• damage to the central nervous system: convulsions and depression of consciousness.

Classification of the degrees of clinical manifestations of fever:

1. Nonspecific symptoms, minor bleeding.
2. Attachment of spontaneous bleeding, for example, from the gums, gastrointestinal tract.
3. Manifestations of 2 degrees and decreased blood pressure, cold damp skin, weak pulse, tachycardia.
4. State of shock.

If antishock therapy brought positive result, the signs of hemorrhagic fever quickly disappear, the person recovers without any health consequences.

In cases where treatment is ineffective, death occurs within 24 hours.

Diagnostic measures

In addition to clinical manifestations, there are criteria that facilitate the diagnosis of hemorrhagic fever:

1. Decrease in the number of cells responsible for coagulation (platelets) in the peripheral blood.
2. Blood thickening is more than twenty percent compared to normal.

When diagnosing classic fever, the doctor relies on leading symptoms and laboratory tests. In addition, visiting places where cases of infection have been identified can lead to the correct diagnosis.

To make a final diagnosis, two main laboratory tests must be performed:

1. Virological - isolation of the virus, its identification, characterization of the basic biological properties. This requires a specialized laboratory. Most often, blood and swabs from the mucous membranes of the nasopharynx are used.
2. Serological - detection in serum of protective proteins (antibodies) against the causative agent of fever. A sign of the presence of the disease is an increase in the number of antibodies to the virus in the blood. Downside The test is a possible response to other viruses, so there is a possibility of a false positive reaction.

In laboratory conditions, the disease is confirmed by isolating the virus from the blood or based on an increase in antibody titer in paired sera

Differential diagnosis

Classic dengue fever is differentiated from influenza, measles, hemorrhagic fever - from meningococcemia, malaria, sepsis, yellow and mosquito fever, as well as other hemorrhagic fevers.

Only laboratory tests are decisive, since it is almost impossible to make an accurate diagnosis based on clinical signs alone.

Dengue fever treatment

On modern stage There are no medical developments or drugs aimed at eliminating the virus. Treatment is based on stabilizing the patient's condition through symptomatic therapy:

1. Prolonged high temperature contributes to the development of dehydration, so drinking plenty of fluids is necessary, which also helps reduce intoxication.
2. At temperatures above 38 °C It is recommended to take antipyretic drugs.
3. Painkillers are indicated for severe pain.

With a mild course of the disease, the classic form can be treated on an outpatient basis under the guidance of a doctor.

Hemorrhagic fever is an indication for hospitalization. Therapy is carried out only in a specialized closed hospital.

Prognosis, complications and consequences

If a viral infection is detected early and adequate symptomatic therapy is prescribed, the prognosis is favorable. When a severe form develops, timely treatment is also of paramount importance, reducing mortality by 10%.

In case of complications (encephalitis,) the prognosis worsens.

In addition, after an infection, immunity lasts up to 2 years. The disease reoccurs in the local population and only in a dangerous hemorrhagic form (mortality rate up to 50%).

Vaccination and other preventive measures

The main measure to prevent viral infection is to control the pathogen vector. Recommended:

In 2015, a vaccine against dengue fever was developed, which the World Health Organization suggests for use in countries with periodic outbreaks of the disease. Its use is also advisable for tourists traveling on vacation to countries with a risk of infection.

Before visiting tropical countries Where there are outbreaks of a dangerous infection, it is recommended to increase your own immunity: eat fresh vegetables and fruits, play sports, and stay in the fresh air for at least 3 hours a day. And after returning home, be sure to consult a doctor and undergo the necessary tests to rule out the development of Dengue fever.

Specific timing of exacerbation of the epidemiological situation is predicted as follows:

The carrier of the infection is mainly the Egyptian biting mosquito - Aedesaegypti and some of its other relatives. And for breeding, this type of mosquito, like others, prefer to choose stagnant bodies of water or, as they often say, wetlands. (*But these can also be small tanks, as well as showers and toilets.) Thus, the peak of the epidemic coincides with the beginning of the rainy season - April May(but it’s better to focus on the rain), and subsequently the situation subsides a little, but there is still a chance of infection. The mosquito is only a carrier - there is no need to blame it for all the bad things. The source of the disease is humans and some primates. Therefore, when the number of carriers decreases due to the actions of doctors and natural processes, then the epidemiological situation decreases.

There is no warning as such about the beginning of the epidemic, the locals already know. If they sit down and make a notification, they will say a couple of times on the news and that’s enough. Previously, this problem was more acute in Thailand, there was a high mortality rate, not like now, then the notification was as necessary. And now local medicine has learned to recognize and cope with this disease well.

How to protect yourself?

It’s very simple to protect yourself, avoid the carriers – the Egyptian biting mosquito – Aedesaegypti:

Egyptian biter, a distinctive feature is the presence of white dots on a black body.

1. Most of all, the mosquito loves to be in a shady area.

2. An interesting feature of the mosquito is that most of all it loves human blood and the blood of primates.

3. The most favorite breeding places for mosquitoes are places of stagnant water - wetlands or water filled with organic decay products, various leaves, grass, etc. But the most dangerous of them for humans can be the shower and toilet.

4. The increase in the population of this mosquito is facilitated by uncontrolled urbanization, accompanied by the emergence of urban areas without a centralized sewerage system, littered with household garbage, many components of which, for example, cans, serve as an excellent breeding ground for mosquitoes;

5. As a precaution, it is recommended to wear clothes with long sleeves, and use mosquito spray.

Dengue fever is a manifestation of an acute form of a transmissible viral disease that affects absolutely all organs of the human body. This disease has no clear restrictions regarding age and gender, which is why it can be diagnosed in both children and adults. The pathological process is characterized by the following signs:

• severe intoxication of the body;
• fever;
• skin rashes;
• significant enlargement of lymph nodes.

Dengue fever is common in the following regions:

1. African.
2. South and Southeast Asian.
3. Oceania region.
4. countries in the Caribbean region.

The virus is usually found in climate zones such as tropical and subtropical. According to experts, dengue fever is one of the most dangerous tropical diseases. Of course, there are worse diseases in these regions, but dengue is one of the most dangerous in terms of the scale covered in the human body and the range of harmful effects it has on every organ. Therefore, it is sometimes called tropical fever. This type of infection multiplies quite quickly. Recently, cities such as:

• Phuket (Thailand);
• Hanoi (Vietnam);
• Beijing, China).

Over the past 20 years, there has been a significant increase in the number of people contracting the disease in all regions. The dengue virus can also have toxic effects on the human body. It mainly affects:

1. liver.
2. kidneys
3. heart.

A relapse of the disease is possible. Immune protection can last no more than two years, and then the infection will recur, only the source will be another focus.

The causative agent of the infection is infected mosquitoes and other exotic insects, as well as animals that live in those regions. Another carrier of infection is a sick person. After 4–5 days, inflammation appears at the site of the bite, and the virus multiplies and accumulates there. When the incubation period expires, the virus enters the blood.

Dengue fever is a flu-like illness. The causative agents of the disease belong to the antigenic group of arboviruses.

The dengue fever virus is equally dangerous for both children and adults.

Classification

Dengue fever has four serotypes:

• DEN 1;
• DEN 2;
• DEN 3;
• DEN 4.

There are two main groups:

1. Classic form of dengue fever (primary disease).

2. Hemorrhagic form of fever:

1. Filipino.
2. Thai.
3. Singaporean.

This is an acute form of classic dengue fever.

Also considered following forms:

• joint fever;
• bone crush fever;
• five-day fever;
• seven days fever;
• giraffe fever;
• date disease.

The course of the disease is also classified according to severity: mild, moderate, severe, fulminant. The latter form has extremely negative forecasts, since clinical picture develops very quickly, is characterized by a severe course and a high risk of death.

Symptoms

The incubation period is about two weeks.

Symptoms of dengue characteristic of the classic form of fever:

1. chills.
2. cardiopalmus.
3. interrupted breathing.
4. elevated temperature (often above 39 degrees).
5. muscle pain.
6. feeling tired.
7. rheumatism.
8. lethargy.
9. insomnia.
10. sudden loss of strength.
11. completely refusing to eat.
12. dehydration.
13. nausea and vomiting.
14. dizziness.
15. headache.
16. the appearance of a rash on the face.
17. swelling of the face.
18. redness of the eyes, progressing to conjunctivitis.
19. sore throat.
20. rash with itching and skin irritation.
21. possible hemorrhages in some areas.
22. the appearance of blisters on the skin.

The symptoms of dengue hemorrhagic fever are:

• cough;
• irritation and inflammation of the throat;
• nausea and vomiting;
• refusal to eat;
• elevated temperature, often above 39 degrees;
• abdominal pain;
• an increase in the size of the lymph nodes;
• weakness;
• emotional instability;
• increased liver volume;
• vomiting with the release of blood masses;
• hemorrhage inside the gastrointestinal tract;
• skin laxity;
• a sharp decrease in pressure;
• cardiopalmus.

As mentioned above, there are four grades classified, each of which has its own clinical features.

First degree:

1. general intoxication of the body.
2. In the elbow bend, hemorrhages are possible with strong pressure.
3. acute thrombocytopemia.

Second degree:

• all manifestations of the first degree;
• in an acute form, hemoconcentration;
• unexpected hemorrhage in the gums and gastrointestinal tract.

Third degree:

1. all signs characteristic of the second degree.
2. excessive excitement.
3. profound circulatory failure.
4. hemoconcentration and thrombocytopemia.

Fourth degree:

• everything inherent in the third degree;
• state of shock;
• changes in blood pressure;
• thrombocytopemia;
• hemoconcentration.

Signs of fever of the third and fourth degrees:

1. At the height of the illness, the patient experiences severe anxiety.
2. cold, mucus-covered extremities.
3. the torso remains warm.
4. laxity of facial skin.
5. chapped lips
6. appearance of exanthems.

Diagnostics

Successful treatment of the disease requires diagnosis at an early stage of a progressive infection. Diagnosis must be made correctly, because the methods for identifying the disease are different for each form. The disease can be recognized using various laboratory and clinical tests. But to determine the form, degree of harm caused to the body and the grouping of organs on which it will happen or has already happened dangerous influence, is possible through instrumental diagnostics.

Laboratory research methods include tests such as:

• blood analysis;
• Analysis of urine;
• detection of the presence of antibodies;

Antibodies can be detected in the human body by performing the following reactions:

1. response to complement fixation.
2. reaction to inhibition of hemagglutination.
3. neutralization reaction.
4. PCR is the detection of viral DNA, which helps identify viruses of various types.

Diagnosing dengue disease is not easy, because there are a large number of diseases with similar symptoms, recognizing the correct diagnosis in them is a difficult task.

Diseases that have the same characteristic symptoms as dengue fever:

• chikungunya fever;
• pappataci fever;
• yellow fever;
• Marburg fever;
• Lassa fever;
• Zika fever;
• meningococcemia;
• sepsis;
• malaria.

Treatment

Treatment of dengue fever is not an easy and lengthy process. It all depends on how the disease manifests itself and what possible consequences may arise. If the diagnosis is confirmed, urgent hospitalization is required.

The prescription of drugs directly depends on the form of the disease. If this is the classic form, then they mainly prescribe:

1. vitamins.
2. antihistamines.
3. painkillers.

You should drink water in large quantities to avoid dehydration. The patient is also prescribed strict bed rest.

For the hemorrhagic form, treatment is prescribed such as:

• infusion therapy;
• glucocorticoids;
• oxygen therapy;
• introduction of plasma and plasma substitute into the body;
• use of coagulants.

Possible complications

The consequences of dengue fever can cause not only complications, but also death.

Possible complications include:

1. encephalitis.
2. meningitis.
3. infectious-toxic shock.
4. polyneuritis.
5. pneumonia.
6. psychosis.
7. otitis.
8. mumps.

All these complications can lead to the chronic form of these diseases. In addition, some of the previously listed diseases lead to death.

Prevention

IN this moment The main route of infection is mosquitoes. Therefore, the main prevention remains the control of infection vectors. In addition, a person should be vaccinated before traveling to potentially dangerous regions. At the first signs, you should urgently seek medical help.

Forecast

With the classic form of dengue fever, all patients have a favorable chance of recovery. If the disease is hemorrhagic, then the probability of death is 50%.

Dengue fever is characterized as a viral disease that causes a sharp rise in body temperature, intoxication and loss of strength. Accompanied by specific rashes on the skin and mucous membranes, provokes bleeding. It can develop into a severe form of the disease with the formation of serious abnormalities and lead to death.

What is dengue fever

The main carriers of the virus are female Aedes aegypti mosquitoes. When they bite people, they not only become carriers of the disease, but within 5-12 days from the moment signs of Dengue fever appear, they act as the main sources of infection for all uninfected mosquitoes. The development of the virus occurs at a minimum temperature of 22 degrees, which is typical for the tropics (subtropics).

Another mosquito species that can cause dengue fever is Aedes albopictus. These insects are distinguished by their resistance to cold and survival. The incubation period of a virus that has entered the body of a mosquito is up to 10 days. Females of both mosquito species have the ability to infect throughout their existence, which is limited to three months. In turn, people are very susceptible to the virus.

Children, including infants, and tourists are more often susceptible to Dengue fever when they are in the area where infected people live.

Forms of the disease and their characteristics

There are the following forms of Dengue fever:

1. Classic. It is a benign course of the disease with the absence of hemorrhagic syndrome. The characteristic signs of classic fever are:

• Intoxication, manifestations, lethargy.
• 2-wave fever after the incubation period in the first day is marked by an increase in temperature by 2-5 degrees from the normal value. After 3 days, the temperature normalizes, but soon reaches critical values ​​again.
• Runny nose, severe chills.
• Rapid pulse at first and slow after 3 days.
• Redness and inflammation of the eyes.
• Fear of bright rays of light.
• Headache radiating to the eyeballs.
• Muscular, vertebral, joint and pain in the extremities (immobilization is possible).
• Loss of appetite, bitter taste.
• Sleep problems.
• Enlarged lymph nodes.
• In severe cases, vomiting, delirious speech, and loss of consciousness are observed.
• The appearance of a specific rash on days 5-6 with an initial focus on the chest, shoulders and further spread throughout the torso and limbs. A specific rash is expressed in the form of spots and reddish asexual compactions on the surface of the skin. Accompanied by itching sensations followed by the formation of peeling.

• 2-wave fever.
• Chills all over the body.
• , dry throat.
• Headache.
• Joints and muscles rarely hurt.
• Redness of mucous membranes.
• The appearance of a pinpoint rash is accompanied by redness with inside elbows and under the kneecaps.
• Development of a rash with reddish lumps on the skin surface of the body after 3-5 days. Further spread of the rash is the facial part, limbs. All this creates an itchy effect with the appearance of peeling.
• Stomach cramps, abdominal pain, vomiting blood.
• Constant vomiting and profuse bowel movements of liquid consistency are possible.
• Soreness and enlargement of the liver.
• Stabilization of temperature indicators occurs within 2-7 days. The recovery phase begins.

• Hemorrhagic syndrome. Hemorrhages occur in the stomach, intestines, nasal, brain, uterine areas, etc.
• Hypovolemic shock. A pathology characterized by significant deprivation of fluid due to blood loss and copious intestinal bowel movements of a liquid structure. As a result, the amount of circulating blood decreases. The following changes are observed: a falling jump in blood pressure, loss of consciousness, pupillary dilatation, reflex disorders, coldness, pallor and cyanosis of the skin, muscle cramps and a weak pulse.

3. Atypical. Accompanied by deviations in the form of:

• muscle pain;
• rash present with classic fever;
• absence – hallmark atypical fever.

Causes of Dengue Fever

A number of factors influencing dengue fever infection:

• Visiting countries in Africa, Southeast Asia, the Caribbean and the islands of Oceania.
• Contact with infected mosquitoes.
• Being in areas inhabited by sick people, primates and bats, which are considered a source of disease for uninfected mosquitoes.

The danger of Dengue fever (video)

Symptoms and degrees of fever

General symptoms of the disease manifest themselves in the following points:

• Temperature jump to 39-41 degrees.
• Increased heartbeat, followed after some time by a weakening pulse.
• Lack of appetite/ .
• Inactivity due to joint and muscle pain.
• Skin and mucous rashes of a specific type.
• Feeling of itching, skin peeling.
• Hyperemia/subcutaneous hemorrhages.
• Lymphatic, almond inflammation.
• Enlarged liver.
• Bleeding of various origins.

• bloody cough/vomiting;
• convulsions;
• psychosis;
• severe hypotension, hemoconcentration and thrombocytopenia;
• acrocyanosis (blue skin discoloration);
• prolonged pain syndrome;
• development of certain pathologies;
• state of shock.

• First (initial). It manifests itself in the form of an increase/decrease in temperature, general intoxication of the body, and slight fluctuations in the number of platelets in the direction of decrease. Hemorrhages occur when a tourniquet is applied.
• Second. Additionally, random subcutaneous and gastrointestinal bleeding appears. Blood thickening (hemoconcentration) occurs due to a decrease in plasma and a significant drop in platelet levels (thrombocytopenia).
• Third. A feeling of excitement and circulatory deficiency (poor blood circulation) are added.
• Fourth (hard). Accompanied by a deep state of shock and a noticeable decrease in blood pressure.

Diagnostics

1. Establishing the fact of visiting locations with an increased risk of infection.

2. Presence of characteristic symptoms:

• temperature below 40;
• unbearable headache;
• squeezing of the eyeballs;
• nausea, vomiting;
• muscle and joint pain;
• rash;
• sometimes enlarged lymph nodes.

• consultation with specialists (epidemiologist, infectious disease specialist);
• determination of viral DNA in the blood within 2-3 days from the moment of infection using a polymer chain reaction (PCR method);
• establishing the type of virus and then prescribing the required preventive measures, which is the administration of immunoglobulin from a person who has had the corresponding type of fever;
• analysis for antibodies, identifying their activity against a viral pathogen;
• blood test to look at your platelet count (should be low) and red blood cell count (should be high).

Treatment

• Antipyretics, with the exception of drugs that can cause bleeding. These include Aspirin, Ibuprofen and similar medications.
• Antihistamines to eliminate itching sensations.
• General strengthening in the form of injections containing vitamin complexes and glucose solution.
• Detoxification using plenty of fluids, enterosorbents and saline (intravenously).

• drip administration of glucose, vitamins and saline;
• transfusion of plasma and its analogues;
• the use of glucocorticosteroids in order to normalize mineral, carbohydrate and protein balance and eliminate the occurrence of shock;
• oxygen nutrition;
• the use of drugs aimed at increasing blood clotting.

Self-medication for Dengue fever is contraindicated, and if symptoms are detected, immediate medical attention is required.

Forecast and prevention, vaccination

• timely protection from contacts;
• wearing light-colored clothing with long sleeves and trousers;
• installation of mosquito nets above the bed and on the windows;
• placement of fumigators in the living space;
• the use of personal protective equipment (creams, sprays and other repellents) to repel mosquito vectors;
• use of spray chemicals to kill insects;
• preventing mosquitoes from entering water containers, changing and cleaning it regularly;
• administration of immunoglobulin obtained taking into account the serotype from a recovered person.

Dengue fever, or joint fever, is a naturally occurring infectious disease caused by a group of arboviruses (a type of virus transmitted by arthropods). Depending on the form, it occurs like the flu with a rash on the body, myalgia and joint pain, or is accompanied by hemorrhagic syndrome, spontaneous bleeding, shock, collapse, and often leads to death. The disease is caused by the dengue virus, which is transmitted by tropical mosquitoes. There are no etiotropic drugs that affect it, so therapy is based on eliminating symptoms and the use of hemostatic and anti-shock measures.

Features of the disease

Dengue fever is a vector-borne disease caused by the virus of the same name, found in tropical and subtropical climate zones. Cases of mass infection have been identified in 110 countries, Australia, Africa and Oceania, on the South American continent, southeast Asia, and the Mediterranean coast.

Outbreaks of epidemics depend on the seasons and are observed during the rainy season. In endemic areas, usually in cities, up to several hundred thousand people are infected per year; precedents are recorded outside the outbreak areas during the migration of already infected people or the importation of carrier mosquitoes.

Fever manifests itself in two independent forms, differing in symptoms and consequences of infection:

• Classic. It is accompanied by a feverish state, pain in the joints and muscles, the development of lymphadenitis (inflammation of the lymph nodes) and leukopenia (decreased white blood cells).
• Hemorrhagic. The disease is severe and is characterized by impaired vascular permeability. Hemorrhagic diarrhea develops due to a decrease in the number of platelets in the blood (thrombocytopenia) and a clotting defect. A decrease in circulating blood, proteins and electrolytes causes disturbances in organ function, which leads to shock, becoming the main cause of high mortality rates from the disease (in some areas - up to 50%).

There are cases of atypical and asymptomatic course of the disease, which is associated with the characteristics of the genes of individual individuals.

Causes

Dengue virus

Fever develops as a result of invasion of the human body by an arbovirus from the family Togaviridae, genus Flavivirus. Science knows the virion serotypes from DEN-1-2-3-4, the fifth was established recently, in 2013. All of them differ in antigenic structure, differentiation occurs by the neutralization reaction and HRT titers.

Each strain causes similar symptoms of disease and can provoke both types of fever. Types 2 and 3 have the greatest cytopathic effect.

After the illness, immunity to the pathogen is developed for 2 years and resistance to other types for 2 months.

It has been noted that the hemorrhagic form often develops in people who have previously been ill when they are re-infected with a different serotype of the virus. Disorders of hemostasis, activation of complement and other parts of the system are most likely associated with the immune response and its damaging effects.

The shape of the dengue virus is spherical, the diameter is approximately 40-45 nm. It has an additional lipid bilayer with surface projections and single-stranded unsegmented RNA. Close relatives of the virion are the encephalitis, yellow fever, West Nile, and Zika viruses. All of these species are transmitted by arthropods and are therefore called arboviruses.

Extracellular agents are unstable to heat and die at a temperature of about 60 °C, but when dried or frozen to -70 °C they remain active for up to 10 years. They are sensitive to formaldehyde, ether, and are destroyed by proteolytic enzymes.

Transmission routes

Scheme of human infection

The source of infection is a sick person, primates and the bats. The virus is transmitted by yellow fever mosquitoes of the genus Aedes, mainly Aedes aegypti, but also Aedes albopictus, Aedes scutellaris, Aedes polynesiensis.

Having penetrated the body of a blood-sucking insect with the patient’s blood, the pathogen develops in its intestines at a temperature of at least 22 °C, and after 8-14 days it spreads to other parts of the body. The mosquito becomes infectious by excreting the virus in its saliva throughout its life. Mosquitoes are active and reproduce at a temperature of 28 °C - during this period, the maturation time of the virus is reduced to a minimum.

A person is sensitive to the pathogen, so one insect bite is enough for infection. A person bitten becomes infectious the day before symptoms appear and spreads the infection for 5 days after the onset of the disease.

In countries where mosquito vectors live, endemic foci have formed, and outbreaks of epidemics occur periodically. Major pandemics occur when a new serotype of the virus is introduced into an area. The classic form is observed among the local population (mainly children) and visitors. Hemorrhagic fever primarily affects babies under one year of age who have passive immunity to another type of virus - they develop a primary immune response. This group includes children who have previously had the disease and who develop a secondary type of immune system reaction to the new serotype. The virus is also dangerous for elderly and frail people with asthma and diabetes.

Symptoms

After a mosquito bite, the virus multiplies in the cells of the lymph nodes and endothelium lining the cavity of the blood vessels, destroying them. After 5 days, primary replication ends, and the particles enter the bloodstream - they enter the brain, heart, liver and other organs, causing fever and signs of intoxication.

The virus actively multiplies in monocyte cells and tissue macrophages. As a result, the affected particles produce enzymes that affect inflammatory proteins, change the permeability of the vascular walls and the blood coagulation system. These factors influence the development of the form of the disease and its clinical manifestations.

Classic shape

In the classic course of the disease, from the introduction of infection to the appearance of symptoms of the disease, on average, it takes from 3 days to two weeks, more often - 5-7 days. The short-term prodromal period is characterized by decreased appetite and weakness, conjunctivitis and rhinitis.

Often the disease manifests itself acutely, the following are observed:

• dizziness and intense headache concentrated behind the eyes;
• nausea with vomiting;
• chills and a sharp increase in temperature up to 39°, often up to 41°;
• hyperemia and puffiness of the face, scleral injection, in 80% of patients the next day there is general erythema (redness of the skin caused by dilation of the capillaries);
• enlargement of peripheral lymph nodes;
• severe pain in the vertebral and thigh muscles, in the joints (usually in the knees), sometimes noticeable swelling appears;
• rapid heartbeat (on the 2nd or 3rd day, tachycardia turns into relative bradycardia);
• coated tongue and redness on the palate.

Myalgia and arthralgia cause difficulty in movement, which is expressed in a change in gait - it becomes mannered and unnatural. This symptom formed the basis for the name of the disease: dengue - distorted English word dandy (dandy). A decrease in leukocytes (leukopenia) and platelets (thrombocytopenia) is detected in the patient’s blood, and the presence of protein is detected in the urine.

After 3 or 4 days, a sharp drop in temperature is accompanied by profuse sweating. The person’s well-being improves, but pain in the muscles and joints remains. The next wave of exacerbation provokes a repeated increase in temperature over 2-3 days, but with lower rates, which is associated with the penetration of pathogenic agents into the organs.

During the period of apyrexia (between attacks) or during a new exacerbation (approximately on the 6th - 7th day of the disease), the erythema transforms into a multimorphic profuse rash in the form of urticaria or maculopapular formations, which are accompanied by pityriasis-like peeling.

The duration of the disease is up to 9 days until a sufficient amount of antibodies accumulates in the blood. Full recovery, even with a mild course, occurs after 3-4 weeks, in some cases it lasts up to two months, while signs of weakness, pain in muscles and joints remain.

Hemorrhagic form

Petechial rash

The duration of incubation of the hemorrhagic form is 4-10 days. The disease is manifested by a sharp increase in temperature, signs of intoxication, and cephalgia. Myalgia and arthralgia are often absent. The condition is accompanied by:

• conjunctivitis;
• nausea and vomiting;
• disturbance of consciousness (prostration);
• enlarged liver, abdominal pain;
• the appearance of a petechial rash on the skin after 2 or 3 days - the formation of hemorrhagic purpura and extensive areas of hemorrhage (ecchymosis) is possible.

Mainly small vessels are affected. Deterioration of blood aggregation in severe cases is manifested by bleeding gums and nosebleeds, hemorrhages in the internal organs: Gastrointestinal tract, lungs, myocardium.

Damage is indicated by bloody vomiting, black semi-liquid feces (melena), and blood in the urine (hematuria).

On the 3rd - 7th day, 40% of patients develop shock syndrome. It is believed to be caused by autoimmune processes. The condition is characterized by increased permeability of the vascular walls, which leads to plasma leakage, thickening of the blood and a decrease in protein in it (hypoproteinemia). Due to internal bleeding, the patient's blood pressure drops, tachycardia develops, and intravascular coagulation accelerates with the formation of blood clots. Due to lack of blood, internal organs and the brain suffer, cyanosis, loss of consciousness, and sometimes convulsions are observed.

To determine the severity of disorders in the hemorrhagic course of Dengue fever and determine the prognosis, a classification has been created that divides the disease into stages:

Careful monitoring of patients is important. Urgent medical attention is needed if signs of shock appear: weakening and increased heart rate, cold extremities, blue discoloration around the mouth (cyanosis), decreased blood pressure and a sharp increase in hematocrit. Excessive agitation or lethargy may be evidence of shock.

Complications

The virus is carried by blood into the liver, bone marrow, connective tissues, muscles, subjects them to cytolysis, and also penetrates into nervous system, therefore, it is possible to develop complications after the illness, which manifest themselves:

• otitis;
• thrombophlebitis;
• polyneuritis;
• psychosis;
• encephalitis or meningitis;
• cerebral edema;
• mumps, and in men - orchitis.

In pregnant women, the infection can cause miscarriage or fetal death.

Diagnostics

Making a diagnosis when classic painting The disease is not difficult and is based on the typical manifestations of Dengue fever:

• muscle and joint soreness;
• change in gait;
• two-wave flow;
• exanthema and enlarged lymph nodes.

Errors are possible with an atypical course of infection, when the high temperature remains at the same level and there are no rashes.

In the hemorrhagic form, a preliminary diagnosis is established based on signs of intoxication and identification of hemorrhagic diathesis. During examination, a “tourniquet test” helps confirm the assumption: a positive reaction is noted when, after applying a bandage or pneumatic cuff to measure pressure for 5 minutes, new spots of intradermal hemorrhage appear at the site of exposure. The presence of disease outbreaks, mosquito bites, and visits to endemic areas must be taken into account.

Early laboratory blood tests:

• confirm the presence of the virus in the body using PCR or through intracerebral infection of newborn young white mice;
• show the dynamics of the increase in antibodies to the type of virus introduced and its related species using serological studies of RPHA or RSK, enzyme immunoassay testing;
• detect a decrease in the number of white blood cells and platelet mass, metabolic disorders in the direction of decreasing pH (metabolic acidosis);
• show a moderate increase in the enzyme transaminase in the liver, which is associated with leukopenia and thrombocytopenia.

Severe fever leads to plasma leakage and blood thickening, so examination reveals an increase in hematocrit (red blood cells) and a decrease in albumin concentration (hypoalbuminemia), which indicates movement of exudate from the vascular space. If there is a noticeable accumulation of fluid in the abdominal cavity and pleural effusion, pathology is detected during a physical examination. The beginning of the process is difficult to detect, so ultrasound examination is used.

The classic version of Dengue fever is differentiated from influenza, yellow fever and pappataci fever, and in children - from measles and rubella. Hemorrhagic form - from hemorrhagic diathesis of non-infectious nature and other types of viral invasions, similar in clinical manifestations - chikungunya, Crimean and Omsk, yellow hemorrhagic fever, etc.

Treatment

Polyion solution

Etiotropic therapy for Dengue fever is not carried out, since methods to combat the virus do not yet exist. Measures are being taken to relieve symptoms of the disease:

• For severe joint pain, painkillers are used.
• For insomnia, delirium and agitation, barbiturates, bromides or tranquilizers are prescribed.
• If dehydration develops due to high fever and vomiting, frequent drinking is recommended. A pronounced disturbance of the acid-base balance towards a decrease in pH (acidosis) and an increase in hematocrit (red blood cells) requires infusion therapy: intravenous infusion of glucose, alkaline and electrolyte solutions of sodium chloride and bicarbonate, Hemodesa.
• For severe pain and intoxication, the use of Prednisolone is indicated.
• When a secondary infection occurs, antibiotics are used.

In case of shock, oxygen therapy is indicated - the use of oxygen, cardiac medications. Plasma or its substitutes are injected intravenously until normal body temperature, respiration and pulse are restored. Polyionic solutions are used until the hematocrit level decreases to 40%.

Prognosis and prevention

In sporadic cases of dengue fever, the prognosis is usually favorable. During extensive epidemics, 0.5% of deaths were recorded; during periods of individual outbreaks, mortality reached 2 and even 5%, mainly in childhood. With the hemorrhagic form, about 40% of patients die.

Disease prevention in epidemic areas includes the following measures:

• extermination of mosquitoes and treatment of areas where offspring live;
• the use of fumigators, repellents and nets to block access to the premises;
• wearing long sleeves to protect against bites;
• compliance with sanitary standards and storage of water in closed containers;
• isolation of patients and avoidance of contact with the carrier until the period of illness is over.

It is possible to prevent the spread of infection from endemic areas through quarantine measures.

Currently, the only vaccine against Dengue fever is CYD-TDV, which is based on weakened strains of 4 serotypes of the virus. It is approved for use after 9 years, but its final qualification has not yet been carried out. Research results have shown that the effectiveness of vaccination in treating infection remains at 60-79%. Controversy arises due to cases of severe disease development due to the use of the vaccine in children, therefore, further testing and new developments are required due to the discovery of a new fifth virion.