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Yellow fever

The fever yellow is a disorder that is transmitted by the bite of infected mosquitoes . A common disease in Central, South America, and sub-Saharan Africa. Although anyone can get the disease, older people are most at risk of serious infection .

What is yellow fever?

The yellow fever is a viral hemorrhagic disorder acute character that transmit infected mosquitoes. The fact that it is called “yellow” is due to the jaundice that certain patients present as a symptom of the disease.

It is an endemic virus that occurs especially in tropical areas of Central Africa, Central America and South America .

Throughout history there have been various yellow fever epidemics, which arise when the virus spreads in densely populated areas, and in which a high percentage of the population does not have immunity to the disease due to lack of vaccination.

Today yellow fever can be prevented with a vaccine ; a single dose is enough to be immune to the disease, without the need for any booster dose.

Types of yellow fever

The living beings most affected by this disorder are people and monkeys. Transmission occurs from one animal to another, as well as through the bite of a mosquito. Depending on their different forms of transmission, three types of yellow fever are differentiated.

  • Jungle: as its name suggests, it is a disease that occurs in tropical forests. It develops as a result of the bite of a mosquito that carries yellow fever. Although it is not very common, it greatly affects your monkeys; these in turn can infect other mosquitoes, which can transmit the disease to those who enter the jungle.
  • Intermediate: yellow fever that occurs in the savannah of Africa is known as such. It is characterized by giving rise to several cases at the same time in separate populations.
  • Urban: in this case it is the Aedes aegypti mosquito that acts as a transmitting agent in densely populated areas. It can lead to large epidemics in which the virus is easily transmitted from one person to another.

Phases of the disease

A total of four phases of the disease can be established, through which practically 100% of the patients affected by it pass.

  1. Incubation: begins at the same moment in which the individual receives the bite of the mosquito that transmits the virus. The first signs of yellow fever appear between three and six days later. During this period of time the virus spreads through the body.
  2. Acute phase: a few days after the bite has occurred, the first symptoms begin, which are very similar to those of any other infection: high fever, nausea, vomiting, headache , lack of appetite. Jaundice also arises as a typical sign of the disease.
  3. Remission: Symptoms usually last a few days, after which they begin to gradually subside. Some patients recover gradually, while others relapse.
  4. Intoxication: and finally, after several days of remission, some of the patients affected by yellow fever enter what is known as the intoxication phase. In it, the symptoms of the acute phase are repeated, although with greater virulence: fever, bleeding, abdominal pain … There may even be failure in certain organs such as the kidneys or the liver.

Causes of yellow fever

The direct cause of the disease in humans is the bite of an infected mosquito, usually of the Aedes or Haemagogus genera . The virus can also be transmitted between monkeys, and even from monkeys to humans through mosquitoes.

Although it is not usual, a combined cycle can also occur . First, the infected mosquitoes bite monkeys, who transmit the disease to humans. And secondly, other mosquitoes, after biting humans affected by yellow fever, transmit it to other humans.

Most common symptoms

The symptoms of yellow fever get worse as the disease progresses. In the initial phase, the signs are very similar to those of any other infection: fever, headache, nausea, loss of appetite, dizziness …

As yellow fever progresses and what is called the toxic phase begins, the symptoms are much more serious, even life threatening: abdominal pain, nose and mouth bleeding, kidney and liver failure, seizures …

Diagnosis and treatment of yellow fever

The diagnosis of yellow fever is complicated, especially during the acute phase since the symptoms are very similar to those of other diseases such as malaria, dengue or typhoid fever , among others.

The doctor first of all takes the medical history of the patient, taking into account whether he has recently traveled to endemic countries of the disease , whether or not he is vaccinated against yellow fever, and the symptoms he presents.

The diagnostic test to detect the disease is a blood test , in which antibodies and specific substances related to the virus can be determined.

To date, there is no antiviral drug that is useful to treat the disease. Therefore, once yellow fever has been confirmed, the treatment consists of combating the symptoms: providing fluids, keeping the blood pressure at the appropriate values, providing dialysis if the patient has entered the toxic phase and has kidney failure … In some cases , plasma transfusion is necessary to replace blood proteins, which improve clotting.

You may also be interested in:   Ebola

Complications and mortality

In a high percentage of cases, those patients affected by yellow fever show a recovery of symptoms between three and four days after their appearance . Around 15% enter the toxic phase, in which the symptoms are very serious, such as nose and mouth bleeds or impaired kidney and liver function. It is estimated that 50% of patients die during the toxic phase .

To date, estimates indicate that yellow fever is responsible for 30,000 annual deaths , especially in underdeveloped countries where the population does not have access to the vaccine.

Yellow fever vaccine

As we have pointed out, yellow fever is typical of countries in sub-Saharan Africa and tropical areas of both Central and South America. Thus, the disease poses a risk both for the inhabitants themselves and for the travelers .

In the case of travelers, the risk of being infected by the virus is determined by various factors: immunization status in relation to the vaccine, destination of the trip, season of the year, activities carried out during the trip and exposure time.

Yellow fever is a disease that can be prevented by vaccination. To date, the vaccine contains live attenuated 17D strain viruses , which are grown in chicken embryos. It is the only approved vaccine in Europe.

Vaccination indications

The yellow fever vaccine is recommended for children over nine months of age and adults who are going to travel to endemic countries of the disease. There are certain countries that even require a vaccination certificate as a requirement to enter them.

The vaccine is administered through intramuscular injection . It is highly effective since both children and vaccinated adults are protected against the disease.

In recent years, a large selection of vaccination campaigns have been carried out in certain areas of Africa, in which cases of yellow fever have been reduced by up to 82%.

Side effects

In the same way that the administration of any other vaccine, the yellow fever vaccine also has a series of side effects that are interesting to know: pain in the area where the injection has been administered, fever and headache .

Contraindications

The yellow fever vaccine is not recommended for babies younger than six months of age . Nor is its administration recommended to those people who show sensitivity to one or more components of the vaccine, as well as those whose immune system is weakened.

Precautions

There are certain population groups in which the yellow fever vaccine should be administered with caution since the risks are moderate.

This is the case of babies between six and nine months of age , in whom there is a certain risk of encephalitis after vaccination. Similarly, in adults over the age of sixty , there is a risk of developing a certain neurological disease.

In the case of pregnant women , some studies have shown that there is a relative risk of transmission of the live virus to the fetus. And finally, breastfeeding women , the live virus can be transmitted to the baby through breast milk.

Disease prevention

In addition to vaccination, there are a series of additional precautionary measures that it is advisable to know before traveling to countries where the risk of contracting the disease is high.

  • Repellent: the use of repellent is highly recommended, which should be applied several times a day; Avoid those areas of the skin where there are wounds or irritations. Ideally, you should buy the repellent in the country of destination.
  • Appropriate clothing: it is also advisable to pay special attention to clothing to avoid bites. The ideal is to use light-colored garments that cover the entirety of both the arms and the legs.
  • Humid places: do not forget that mosquitoes breed in humid places, especially those where the water is stagnant. Therefore, it is important to avoid possible sources such as ponds or swimming pools.
  • Medical assistance: before the slightest symptom of yellow fever, it is important to see a doctor as soon as possible to make the diagnosis and determine the most appropriate treatment.

Yellow fever in the world: outbreaks

One of the last known yellow fever outbreaks in the world has taken place in Brazil . Between December 2016 and March 2018, more than 2,000 cases have been confirmed and 676 deaths have occurred .

Well, according to a study published in the journal Science, this outbreak originated in primates in wooded areas , after which it was transmitted to humans.

The researchers responsible for the study observed that in a period of just four days, human cases lagged behind those of primates. In addition, the risk of yellow fever was higher in those who lived in wooded areas, in which mosquitoes bite primates and subsequently transmit the virus to humans. In addition, in areas close to the origin of the outbreak, 85% of the cases occurred in men.

Conclution

Yellow fever is a viral disease that can be prevented by vaccination . More and more programs are underway in underdeveloped and developing countries to vaccinate the population and, thus, minimize the impact of the disease.

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Hello Readers, I am Nikki Bella a Psychology student. I have always been concerned about human behavior and the mental processes that lead us to act and think the way we do. My collaboration as an editor in the psychology area of ​​Well Being Pole has allowed me to investigate further and expand my knowledge in the field of mental health; I have also acquired great knowledge about physical health and well-being, two fundamental bases that are directly related and are part of all mental health.

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