Dengue (hemorrhagic type): symptoms, mosquito, treatment

Dengue is a disease that generates a lot of concern. Due to the difficulty in controlling the vectors, their dissemination is easy, especially in times of rain. Knowing how to protect yourself and seek preventive measures is the best way to reduce cases of infection.


What is dengue disease?

Dengue is a disease caused by a virus of the genus Flavivirus that usually causes symptoms very similar to the flu . If left untreated, it usually worsens and reaches its hemorrhagic form, which can be fatal. This version of the disease can also arise due to reinfection by the virus.

It is transmitted through the mosquito Aedes aegypti , the same that spreads yellow fever and Zika. Infection can also happen vertically (from the pregnant mother to the baby), but there is no transmission from person to person.

The disease has been known for a long time, and its first manifestations were described in the 18th century. However, its form of transmission was only discovered in the 20th century.

Since the second world war, dengue has become a global problem, as this event has brought about a huge amount of ecological disturbances that allowed the mosquito vector of the disease to spread throughout the planet.

There are 4 different serotypes of the dengue virus. When a patient is infected by one of them, he is immune to that serotype only, which makes him partially immune. That is, it can still be contaminated by the other 3 serotypes.

All dengue serotypes cause the same symptoms, which makes the task of distinguishing them through an analysis of the clinical picture an impossible task. Are they:

  • DEN-1.
  • DEN-2.
  • DEN-3.
  • DEN-4.

During the first infection, dengue is usually asymptomatic, but there is a possibility that it will evolve and become more severe. Approximately 550 thousand people are hospitalized due to the disease and, of these, about 20 thousand die as a result of the infection.

Initial symptoms usually include high fever (from 39 ° C to 40 ° C), headache , on the body, behind the eyes and in the joints, weakness, the appearance of rashes and itchy skin.

It may happen that the patient loses weight, has nausea and vomiting, which is usually treated with the replacement of electrolytes (minerals present in the blood) and rehydration.

It is very important to focus on preventing the disease, which occurs through the fight against the mosquito. Learn more about this disease, how to prevent it and how to fight it!

Mosquito Aedes aegypti : infection agent

The female of the dengue mosquito can deposit up to 100 eggs on the inner walls of the containers with accumulation of standing water. And these eggs can last up to 1 ½ years.

When they come into contact with water, they develop quickly, giving rise to what we call pupae, which is a cocoon, that is, the stage between worm and adult mosquito.

This embryo takes 48 hours to develop and lives in water for about 1 week.

The big problem is that mosquito eggs can remain inactive for up to more than 1 year even in places with high and dry temperatures. In other words, even if that container or that tire is dry, it is enough for a rain to wet them for the eggs to appear and new mosquitoes to develop.

It takes a period of just 7 days for the mosquito to hatch. This is the reason for concern about hygiene. To give you an idea, it is possible that the eggs are deposited, for example, in the refrigerator motor that, at the time of defrost, creates a puddle in which the egg can hatch.

After this 7-day period, mosquitoes acquire the habit of feeding and reproducing during the day. At this stage, its lifespan is 35 to 45 days. They feed on substances that contain sugar, such as sap and nectar from plants.

This feeding preference, however, is exclusive to males. Females, on the other hand, need iron and other blood proteins to develop their eggs. For that reason, they bite the human being.

The dengue mosquito usually appears in the early morning and late afternoon, preferring to attack in the shade. However, there are surveys that indicate a change, in which the mosquito can bite at any time.

Each female has the capacity to generate 700 new mosquitoes, and the infected mosquito can bite up to 300 people in its 45 days of life.

However, only a few females have the virus in their salivary glands and are able to transmit the disease. According to a survey by the Oswaldo Cruz Foundation, only 1 in 1000 mosquitoes are infected with viruses.

Even if it seems optimistic, this is no reason to stop worrying, since, in addition to dengue, Aedes aegypti is also the mosquito that transmits the Zika and Chikungunya viruses .

What are the types of dengue?

Basically, there are 3 types, which we will understand better below, check out:

Classical dengue

This is the mildest type of the disease, and can often be confused with flu symptoms. It starts suddenly and its symptoms last from 5 to 7 days.

Hemorrhagic dengue

It occurs when the patient infected with dengue undergoes changes in his blood clotting. If hemorrhagic dengue is not treated quickly, it can lead to death.

In general, it affects the individual who is infected for the second or third time. What differentiates this type of classic dengue is the progression of symptoms, because after the 4th day it is possible to notice the appearance of hemorrhages in the patient, due to bleeding from small vessels of the skin and other organs.

Dengue Shock Syndrome (SCD)

It is the most serious type of dengue occurrence on record. It causes the patient to experience a drop or absence of blood pressure, subsequently presenting an almost imperceptible pulse, in addition to:

  • Restlessness;
  • Neurological disorders such as transverse myelitis and Guillain-Barré syndrome;
  • Pallor;
  • Loss of consciousness or decrease (between 0.5% and 6% of cases).

In SCD there are records of several complications, such as:

  • Pleural effusion;
  • Liver failure;
  • Digestive bleeding;
  • Cardiorespiratory problems.

Neurological manifestations can still occur, among them:

  • Delirium;
  • Somnolence;
  • Depression;
  • With the;
  • Extreme irritability;
  • Psychosis;
  • Insanity;
  • Amnesia;
  • Paralysis;
  • Signs of meningitis.

When left untreated, this type of dengue can lead the patient to death.

What is the cause of dengue?

Dengue is caused by a virus and one of the main public health problems in the world. Transmission occurs through the Aedes aegypti mosquito , which grows in standing water and in tropical and subtropical areas.

It is part of the genus of Flavivirus microorganisms , which are also known to cause other types of disease, such as yellow fever and West Nile fever.

Dengue attacks several areas of the body, causing symptoms very similar to the flu and, for this reason, it is very confused with this disease.

How is dengue transmission?

The virus is transmitted through the female mosquito Aedes aegypti . She, which is a little less than 1 cm in size, deposits her eggs in still water that is in proper conditions, that is, deposited in hot and humid places.

When these eggs are released, they become larvae that give rise to the dengue mosquito, the already famous Aedes aegypti .

It is also possible that the virus is transmitted through the bite of another mosquito of the same genus, Aedes albopictus , but the occurrence of these cases is significantly less.

Transmission actually occurs when a person is bitten by the female mosquito (males do not transmit the disease because they do not feed on human blood). After a period ranging from 5 to 15 days, the first symptoms begin to manifest.

As the mosquito bites both humans and monkeys, the observation of these animals can serve as a way of controlling and identifying an outbreak, therefore, as in the case of yellow fever, pursuing these animals is not only wrong but harmful to the prevention work of disease.

Although it can be transmitted by blood transfusion or organ transplantation, the dengue virus is not transmissible from person to person, but only from mosquitoes to humans.

When a mosquito is infected with the virus, it can carry the disease agent for life and spread dengue until it is fought

Dengue transmission is rare at temperatures below 16 ° C, it usually occurs around 30 ° C to 32 ° C, preferring tropical and subtropical areas, as this is where the mosquito is most likely to reproduce successfully.

Groups of risk

Anyone can be bitten by the dengue mosquito. However, those most at risk of death are the elderly and patients with chronic diseases.

In general, the elderly acquire more severe forms of the disease, subject to the need for hospitalization, while the chronically ill are more exposed to the serious consequences.

In addition, patients who have previously been infected with dengue are more likely to develop severe forms of the disease.

As risk factors are objects that can accumulate standing water and are not regularly cleaned. These locations allow the mosquito to proliferate. For this reason, hot places with a tropical and subtropical climate are also at risk.

What are the symptoms of dengue?

The incubation time of the virus in the body is about 5 or 6 days, making this an asymptomatic phase.

After this period, symptoms appear, usually from the 5th day after the mosquito bite.

The initial symptoms can still be confused with other diseases, such as:

  • Yellow fever;
  • The flu;
  • Malaria;
  • Leptospirosis.

With that, the symptoms of dengue vary according to the type, they are:

Symptoms of classic dengue

Common dengue may manifest:

  • Extreme tiredness;
  • Fatigue and pain in the body;
  • High fever with sudden onset;
  • Severe headache;
  • Pain behind the eyes, which gets worse when the patient moves them;
  • Loss of taste and appetite;
  • Measles-like patches and rashes on the skin, especially on the chest and upper limbs;
  • Pain in bones and joints;
  • Nausea and vomiting;
  • Weight loss;
  • Dizziness.

The patient may also be asymptomatic or have very mild signs of the disease.

When there are red spots on the skin, bleeding (nose and / or gums), severe and continuous abdominal pain, as well as persistent vomiting, extra care is needed, as these symptoms indicate an evolution to hemorrhagic dengue.

Hemorrhagic dengue symptoms

Hemorrhagic dengue has the same symptoms as the common type, however, if the fever goes away, other symptoms appear – characterizing this type of the disease. Are they:

  • Breathing difficulty;
  • Strong and continuous abdominal pains;
  • Red spots on the skin;
  • Pale, cold and moist skin;
  • Fast and weak pulse;
  • Loss of consciousness;
  • Bleeding from the nose, mouth and gums;
  • Drowsiness, agitation and mental confusion;
  • Excessive thirst and dry mouth;
  • Persistent vomiting.

The clinical picture in this case is quickly aggravated, the patient then shows signs of circulatory failure and shock, which can lead to death within 24 hours.

According to the Ministry of Health, about 5% of people with hemorrhagic dengue die.

How is the diagnosis made?

At first, the patient can look for a general practitioner to make an initial diagnosis.

In the initial physical examination, the doctor will look for: skin rashes, swollen glands, increased liver, low blood pressure, rapid and weak pulse, redness in the eyes and throat.

You can take the exams at the Health Units, where there are specialized professionals to attend to particular cases of dengue. The responsible professional will confirm the diagnosis by ordering laboratory tests, blood tests or serology for dengue.

Other examinations and tests may also be ordered by the doctor, such as:

  • Platelet count;
  • Electrolytes;
  • Liver enzymes;
  • Hematocrit;
  • X-ray of the chest to identify possible pleural effusions (fluid in the lungs);
  • Coagulation tests;
  • Serological tests to identify antibodies to the virus.

Loop proof

In cases of suspicion, the snare test is performed, a physical and rapid examination that measures the fragility of the capillary vessels. The method involves measuring the patient’s blood pressure, in which the measuring device tightens his arm and causes a blockage of blood flow in the region. This causes small red dots (petechiae) to appear in the area. The greater the number of these points, the greater the tendency to bleed.

Treatment for dengue

Unfortunately, there is no specific treatment for dengue. In most cases, the symptoms are treated and there is a medical recommendation to keep the body hydrated.

To alleviate those most uncomfortable symptoms, such as headache, the doctor usually indicates paracetamol and other medications, and the prescription varies from case to case.

In milder conditions, the treatment is nothing more than oral rehydration, with homemade or intravenous serum , which is also known as “supportive treatment”.

However, for more severe cases, such as hemorrhagic dengue, the patient may receive intravenous fluids and / or blood transfusions.

Often, the disease progresses to a critical stage because it is confused with others because of similar symptoms, for example the flu and receives the wrong treatment. The difference between them is that dengue does not cause the respiratory symptoms that flu usually causes.


If you have been diagnosed with dengue, you should not use drugs based on acetylsalicylic acid, such as aspirin , as these drugs increase the risk of bleeding.

Medicines to treat dengue

The main drugs used to treat dengue are:

  • Paracetamol ;
  • Dipyrone .

Such drugs are more prescribed, as they are considered the safest for dengue treatment.

It must be emphasized again that drugs based on acetylsalicylic acid, such as aspirin , or non-hormonal anti-inflammatory drugs, such as diclofenac , ibuprofen and piroxicam , should not be used , as these medications increase the risk of bleeding.


NEVER self-medicate or stop using a medication without first consulting a doctor. Only he will be able to tell which medication, dosage and duration of treatment is the most suitable for his specific case. The information contained in this website is only intended to inform, not in any way intended to replace the guidance of a specialist or serve as a recommendation for any type of treatment. Always follow the instructions on the package insert and, if symptoms persist, seek medical or pharmaceutical advice.

Dengue vaccine

Recently, Anvisa changed its recommendations regarding the dengue vaccine. The change occurred mainly because the vaccine, called Dengvaxia , increases the risk of hospitalization or severe dengue in people who have never been infected by the disease.

However, the agency also found that the vaccine’s effectiveness is greater in people who have already been infected. For this reason, the Health Surveillance Agency (Anvisa) recently announced a change to the vaccine package insert.

Understand what has changed:

  • The vaccine should now be restricted to people who have already been infected with dengue and who live in endemic areas ;
  • There was an update in the definition of “endemic area”, which is now defined as a place where at least 70% of people have already had contact with the virus;
  • Now the package insert now contains the contraindications for people who have never had contact with the virus.

How do I know if I should get the vaccine?

Only a medical evaluation can tell you whether or not you should get the vaccine, that is, it depends on how the doctor evaluates the situation, taking into account your medical history and the place where you live.

Who should not get the vaccine?

With the new update, all individuals who have never been exposed to the virus should not get the vaccine. In addition, the vaccine is contraindicated for:

  • Pregnant women;
  • Lactating women (women in the breastfeeding phase);
  • People in a feverish state;
  • HIV / AIDS patients;
  • Severe allergy to any component;
  • People with low immunity, who are undergoing corticosteroid treatments, or radiotherapy and chemotherapy treatments.

How does the vaccine work?

To get vaccinated against dengue, people need to repeat the dose 3 times with an interval of 6 months for each application. The vaccine is free and can be taken by people between 9 and 45 years old who live in places of outbreak of the disease and who have already been infected with the virus.

It works like any other vaccine. A modified and harmless version of the virus is introduced into the bloodstream, which causes the defense cells to produce antibodies to the microorganism.

That way, when an infected mosquito bites the vaccinated person, the body will already recognize the invading agent and fight it before it can even cause symptoms.

It should be noted that it is only used in areas at risk and in people who have already been infected. The idea behind this measure is to decrease the incidence of dengue hemorrhagic cases, which happen more in people who have been previously infected by the virus.

On average, the vaccine’s efficacy is 60% and this percentage varies greatly according to the serotype. Understand:

  • Serotype 1:  efficacy of 58.4%;
  • Serotype 2:  effectiveness of 47.1%;
  • Serotype 3: 73.6% efficacy;
  • Serotype 4: 83.2% effectiveness.


The prognosis for patients diagnosed with dengue is not always positive. Especially those who have been infected previously are at risk of developing the hemorrhagic form of the disease.

Despite this, the disease is usually not so complicated for infected patients for the first time that, normally, with proper medical monitoring, they are able to recover from the infection.

Complications: what causes dengue?

Generally, complications come from Dengue Shock Syndrome (SCD) and can affect an individual with:

  • Neurological and cardiorespiratory complications;
  • Convulsions accompanied by fever (in young children);
  • Pleural effusion;
  • Severe dehydration;
  • Digestive bleeding;
  • Liver failure;
  • Bleeding;
  • Death (when left untreated).

How to prevent?

Although dengue has many outbreaks and occurrences, its prevention is simple, in two ways:

Avoid accumulation of water

The Aedes aegypti is preferred to deposit their eggs in clean water (drinking rarely), so it is ideal not to let accumulate liquid. The main deposits of standing water that provide dengue are:

  • Water tanks, cisterns and gutters: always keep them tightly closed and clean;
  • Bottles: turn them over with the neck down;
  • Tires: throw away the old ones in the correct way and keep the new ones covered;
  • Puddles of water: in any environment, be it company, house or pool, always drain the water;
  • Swimming pools: must be treated with chlorine;
  • Canisters: those we use to put water for pets, wash them frequently, once a week is recommended;
  • Toilets that are rarely used or rarely used: flush at least once a week;
  • Plant pots: put sand or pebbles in all pots;
  • Dumpsters:  must be kept covered;
  • Tanks: must be kept covered.

Other forms of prevention

  • Insecticides: the Health Surveillance Secretariat has been distributing insecticides in certain places, and they are highly efficient as long as they are approved by Anvisa (other insecticides have no proven efficiency);
  • Repellents: suitable for people who usually travel a lot or live in places with a lot of mosquitoes;
  • Insect protection screens: for windows it is not 100% efficient, but they can prevent mosquitoes from entering the house;
  • Vitamin B in supplement form: this type of vitamin works as a repellent, helping the body to emit an odor that can confuse mosquitoes;
  • Fumacê: is a cloud of smoke composed of insecticides (malathion in Brazil) that kills only adult mosquitoes. However, there are places that prohibit it, because it is a neurotoxic compound, that is, they can attack the nervous system of those who inhale it.

Chikungunya and Zika, what do they have to do with Dengue?

Both are also caused by the same mosquito that transmits dengue: Aedes aegypti .

Chikungunya is similar to dengue, what differentiates it are the complications of the patient’s joints and the inflammation accompanied by swelling.

The Zika virus, on the other hand, has the least conclusive information. Its symptoms are also similar to dengue, however they can include: photophobia (sensitivity to light), ulcers in the oral mucosa and constipation.

Dengue in Brazil: 2019 and 2020

Data released by the Ministry of Health report that dengue cases in Brazil in 2019 increased by 7 times. Despite the seasonality of the mosquito circulation, care for standing water and cleaning the land are among the factors most related to this significant increase.

Still in 2019, it was estimated that 690 dengue cases would occur for every 100 thousand people. In general, the southern region was the most critical in total infections of the disease. Presenting the largest increase, by the end of 2019, 88 cities in Paraná entered a situation of dengue epidemic.

In 2020, the situation has not changed much and Paraná continues to issue alerts about new diagnoses and forms of prevention.

In addition to the South, the Ministry of Health reports that the Northeast regions and the states of Espírito Santo and Rio de Janeiro, in the Southeast, may face outbreaks of infection in the coming months of 2020.

Common questions

Does Aedes aegypti transmit dengue?

No . Only the females of the Aedes mosquito transmit dengue, as they are the only ones that feed on blood. In addition, it is necessary that the mosquito is infected with the virus for contamination to occur.

How to recognize the Aedes aegypti mosquito ?

Identifying Aedes aegypti is not as difficult as it seems. It is a small, dark-colored mosquito, with white stripes on the back and legs.

Can an infected person pass the disease on to another person?

No . Dengue does not pass from one person to another directly, such as through air, contact with the hands or through sexual intercourse. For transmission to occur, it is necessary for the virus to infect the mosquito and the person to be bitten.

Contrary to what many people imagine, it is not the contaminated blood of the other person that enters your bloodstream. What happens is that the female mosquito is infected and the virus starts to inhabit its saliva. From there it infects the human being during the bite.

Who has had dengue once is immune or can be infected again?

There are 4 dengue serotypes. When a person is infected, they are immune to a serotype of the virus. This means that she can get dengue 3 more times.

The big problem is that the risk of developing the hemorrhagic version of dengue increases with each infection.

Does the mosquito breed only in clean water?

No! Mosquitoes develop in standing water, whether it is clean or dirty. It turns out that today it is discussed whether females have a greater preference for clean or dirty water, however, regardless of the conclusion, the best way to fight the mosquito is to end up with any and all reservoirs of standing water, dirty or clean.

It is speculated that the term “Dengue” is derived from the phrase “Ka-Dinga pepo”, from the Swahili African language, which describes the disease as being caused by an “evil spirit”. It is the most common arbovirus (diseases caused by arboviruses, such as dengue) that affects humans and, in relation to infectious diseases, it is the most worrying in the country.