Perhaps many have heard of cases when tourists who came from vacation are suddenly struck by an unknown disease called the dengue virus. What is this disease? Is it possible to avoid infection with it? What is dengue fever (virus) treated for? How does it manifest and what organs does it affect? What is the prevention of this disease?
Dengue fever is an acute viral disease with intoxication symptoms, accompanied by muscular-articular pain, fever, and a small rash in the form of point hemorrhages of varying severity. In its antigenic composition, this virus is similar to the viruses of Japanese and West Nile encephalitis and yellow fever. It is not afraid of overdrying and freezing, but lends itself to ultraviolet exposure and heat. Sources and carriers of this infection in addition to a sick person are bats and monkeys.
About the source of dengue fever infection
Dengue virus - what is it? The causative agent of this disease, which until the middle of the 20th century was called bone fracture, or articular fever, is the virus of the Togaviridae family of the genus Flavsvsrus. How dangerous is dengue virus ? How is this disease transmitted? Most dengue fever is common in regions with subtropical and tropical climates: these are Australia, South America, Southeast Asia, Africa and others. This disease also occurs outside the area of its distribution.
This is due to the migration of infected people and the importation of mosquitoes Aedes aegypti and Aedes albopictus - its carriers. These insects are characterized by easy adaptation to cold conditions, the ability to shelter in microenvironments, hibernation and, accordingly, high survival. The winged insect becomes infected 1-2 weeks after the blood saturation of the infected person and carries the acquired dengue virus, of which there are 4 types, about three months. The female mosquito Aedes aegypti lives in a human dwelling, shows the greatest activity at a temperature of 25-28 ° C and bites only in the afternoon. Aedes albopictus mosquito bite's favorite time is early morning or evening hours before sunset.
Being a highly susceptible individual, a person can catch the dengue virus after the first bite. Reproduction of the virus that has entered the body occurs within 3-5 days in the vessels and lymph nodes. Then its particles penetrate the blood and cause the development of viremia, which is clinically manifested by fever-intoxication syndrome. Further, the dengue virus enters the tissues and organs; as it accumulates in the blood, relief of clinical symptoms occurs. Most people with dengue fever are those who have arrived in the regions where the disease is spread, elderly and weakened people, and children, among whom there are the most cases of fatal outcomes, especially in babies under the age of 1 year.
The most widespread epidemics of the dengue virus
Over the past decades, there has been a significant increase in the number of people affected by the dengue virus. So, in 1981 in Cuba, this virus spread to approximately 350,000 people, 10,000 of whom were severely affected, and 158 died. In 1980, nearly 440,000 people fell ill in the People's Republic of China, and 54 of them died. Heavy dengue was first recognized in 1950 during epidemics of the disease in Thailand and the Philippines. This type of fever, which currently affects the population of most Latin American and Asian countries, is one of the leading causes of hospitalization and mortality in these regions of the children's category. Large epidemics are associated with the penetration of an unusual type of virus into a specific region.
Dengue Fever Forms
When dengue is infected for 5-7 days (sometimes from 3 to 15 days), the incubation period is maintained, after which there is an active manifestation of symptoms, from which the whole clinical picture can be combined. In some cases, a prodromal period is allocated that reports the onset of the disease until the onset of certain clinical signs; there is a condition very reminiscent of pre-influenza: constant chills, joint and headaches, general weakness, weakness. Dengue virus, the symptoms of which always include a sharp increase in temperature, proceeds in two forms: classic, characterized by a benign course of the disease, and hemorrhagic, with a high percentage of deaths.
Dengue fever: symptoms of the disease
The classical (benign) form proceeds quite favorably. Moreover, it is characterized by a certain dynamics of the pulse: at first it is quickened, after 2-3 days the indicator of the number of beats per minute is 40 times, which indicates the occurrence of bradycardia. Dengue fever, the incubation period of which is about one week, in its classical form manifests itself in two visits: on the first day, a sharp increase in temperature to 38-41 ° C occurs, after 3-4 days - its normalization.
Then again, a repeated rise to a high mark is the main sign that the dengue virus is present in the body. Symptoms that appear along with an increase in temperature:
- swollen lymph nodes;
- severe chills;
- severe tachycardia;
- weakness, lethargy, fear of light;
- runny nose;
- pressing pain in the eyeballs;
- headache, swelling of the face;
- impaired appetite, sleep;
- the appearance of bitterness in the mouth;
- muscle and joint pain, against the background of which immobilization of the patient may occur;
- vomiting, delirium, impaired consciousness - in severe illness.
Dengue virus, affecting the human body, from the first day causes a cardinal change in its appearance: the patient's face is brightly hyperemic, the tongue is covered, granularity appears in the soft palate, the scleral vessels are expressed, because of photophobia, the eyes are covered.
Rash - the main sign of dengue fever
Around the 6th day, during the second febrile wave, a rash appears on the body - the main sign of dengue fever. In some cases, this symptom may not be observed. First, the rash is localized in the chest, then spreads throughout the body, capturing the limbs. The rash is plentiful, consists of spots of different sizes, small-pointed hemorrhages and red papules. All this is accompanied by severe itching and peeling. In the final period of the disease for another 4-8 weeks, the patient feels weakness, asthenia, muscle and joint pain, loss of appetite, suffers from insomnia.
After recovery, patients develop stable lifelong immunity to the type of virus that caused a specific infection, but there is a risk of re-illness due to a different type of infection. The classical form of the disease occurs if infection occurs for the first time, hemorrhagic is the result of secondary infection of residents of the endemic area or primary infection of newborns who have inherited antibodies from the mother. The interval between the initial and secondary infection can be from several months to five years.
Description of the hemorrhagic form of the disease
Dengue virus (a photo of the manifestations of the disease is presented below) in a hemorrhagic form is more severe than the classic one and is characterized by a high mortality rate. It begins suddenly and at the initial stage is accompanied by high body temperature, a sharp decrease in blood pressure, severe nausea, repeated vomiting, sharp pains in the abdomen, cough, profuse loose stools, development of a spotty-papular rash on the body with spread to the face.
There is an increase in lymph nodes and liver, hyperemia of the pharynx and tonsils, the appearance of blood rashes on the body, hemorrhages in the mucous membrane of the stomach, intestines and brain, uterine bleeding. The patient's condition is rapidly deteriorating, there is an increase in weakness.
There are 4 degrees of hemorrhagic form of dengue fever:
- 1st degree. It is accompanied by fever, signs of general poisoning of the body, blood clotting.
- 2nd degree. Sudden bleeding (from the gums, intradermal, gastrointestinal) is added to the signs of the 1st degree. A blood test shows severe thrombocytopenia and hemoconcentration.
- 3rd degree. Signs of the 2nd degree plus an excited state, cardiovascular failure.
- 4th degree. All symptoms of the 3rd degree, prohibitively low blood pressure and deep shock.
3rd and 4th degrees are otherwise called shock dengue syndrome, which occurs on the 3rd-6th day of the disease. When examining a patient at the very peak of a fever, an unnatural pallor of the face, blue lips, a decrease in pulse pressure, general anxiety, sticky cold limbs, tachycardia, as well as:
- impaired consciousness;
- seizures of individual muscle groups;
- a sharp decrease in blood pressure;
- dilated pupils;
- reflex oppression;
- cyanosis and coldness of the skin.
The duration of the shock is short: the patient may die within 12-24 hours. It is during this period that the largest number of deaths is observed, the average of which is 5-20% of the number of patients with dengue hemorrhagic fever. Patients who managed to survive the peak of the disease begin to rapidly recover. A favorable prognostic sign is the restoration of appetite. The second wave of temperature rise with a hemorrhagic form, as a rule, does not happen. Complications of this disease are psychosis, pneumonia, otitis media, encephalitis, polyneuritis, meningitis, thrombophlebitis, and mumps.
Dengue fever: diagnosis
Recognition of dengue fever takes into account the epidemiological prerequisites: stay in the endemic zone, the incidence rate, outbreaks of infection, mosquito bites. The disease is easily diagnosed during epidemic outbreaks by the signs that determine it: two-wave fever, arthralgia (joint pain), exanthema (rash), myalgia (muscle pain), lymphadenopathy (an increase in the size of lymph nodes). An auxiliary indicator may be a tourniquet test - subcutaneous hemorrhage after application of a tourniquet or cuff to the elbow area.
Key indicators for diagnosing dengue fever:
- abrupt onset, high temperature lasting about a week;
- vomiting of blood, nosebleeds, hemorrhages in the skin, red spots on the skin, bleeding from the gums;
- hemorrhagic symptoms with a positive breakdown of the tourniquet;
- hemoconcentration, enlarged liver, thrombocytopenia not more than 100 * 109 / l, increased hematocrit by not less than 20%.
Dengue shock syndrome is determined by:
- by fast, weak pulse with a decrease in pulse pressure;
- hypotension;
- clammy, cold skin;
- restless condition.
Laboratory disease is confirmed in the first two to three days by isolation of the virus from the blood and by detecting an increase in the antibody titer in paired sera (PTA, RSK, neutralization reaction). This analysis is characterized by more accurate results, but for this kind of research requires a specially equipped laboratory. Serological tests can be carried out, which are an order of magnitude simpler than isolating the virus from the blood and take much less time, but there is the possibility of possible cross-reactions with other viruses, which can lead to a false-positive diagnosis.
Dengue virus treatment
It is important to timely identify the dengue virus, the treatment of which is the speed of medical care. It should be borne in mind: the later the drug is taken, the less its effectiveness.
At the initial stage, drugs based on interferon are effective. Also, for easier transfer of fever, symptomatic drugs are used: antipyretic, antihistamines, painkillers. Patients require detoxification treatment, the mandatory maintenance of optimal water balance and the use of drugs that increase the amount of plasma, if necessary, corticosteroids and antibiotics are prescribed (in the presence of bacterial complications).
To date, there are no licensed dengue fever vaccines. Their development is complicated due to the existence of 4 types of virus (that is, the vaccine must fight all of them - to be tetravalent) and due to the lack of necessary animal models, incomplete clarity of the pathology of dengue fever and the immune responses responsible for protection. There are several experimental vaccines that are currently at various stages of clinical trials.
Dengue fever: prevention
The control of vector mosquitoes is currently considered the only method for controlling or preventing the transmission of dengue virus. In Africa, such mosquitoes spread in the natural environment (leaf axils, tree hollows), in America and Asia - in various containers of artificial origin: concrete tanks, metal barrels, clay vessels in which household water supplies are stored, as well as in other objects, suitable for accumulating fluid. It can be unsuitable containers made of plastic, unnecessary car tires, etc. Dengue fever, the prevention and treatment of which is an important task in countries with warm, humid climates, has spread geographically as a result of international trade in used car tires - an ideal environment for these insects.
In areas where a high incidence is recorded, it is necessary to exclude access of mosquitoes to egg laying sites, namely to artificially created reservoirs of water. It is recommended to arrange appropriate conditions for storing liquid stocks (closed containers that should be emptied and washed at least once a week). When saving capacitive water for technical purposes outdoors, permitted insecticides should be used. Also, to prevent mosquitoes from entering the room, the use of mosquito nets will be relevant. Actual is the fight against bogging of the territory and its clogging. Sometimes such insects are disposed of with the help of small fish and tiny crustaceans - natural natural predators. In regions where the possibility of infection is high, it is required to wear long-sleeved clothing, use personal protective equipment, and use spirals and anti-mosquito evaporators when staying on the street. For a thorough fight against vector carriers requires the mobilization of special communities. The effectiveness of measures taken to combat the virus can be determined by continuous monitoring and epidemiological surveillance of carriers of the infection.
How not to get dengue fever?
A person has a sense of knowledge: new acquaintances, new countries, new trips. If you are going to visit a region where it is possible to become infected with the virus, you should first increase your own immunity. To do this, it is recommended to take a course of vitamins aimed at strengthening the body’s immune system, consume natural freshly squeezed juices, fresh fruits and vegetables, spend more time in the air and exercise regularly. And on a trip, it is advisable to capture protective sprays from insects.
Upon returning to their homeland in case of ailment, it is necessary to consult an infectious disease doctor. High fever, severe headache, skin rash, muscle and joint pain, pain in the area behind the eyes, vomiting, swollen lymph nodes are the main signs that indicate that dengue is present in the body. The vaccine is currently not yet invented for this disease.