Yellow fever is a viral disease caused by an arbovirus belonging to the Flaviviridaes family. It is an acute disease, causing bleeding, which is transmitted by a hematophagous mosquito infected with the virus.
It is called "Yellow" fever due to the icteric dye due to hemolysis that originates in this pathology. This disease usually causes severe symptoms, so much so that more than half of infected patients die during the first 7 to 10 days of the disease.
How is yellow fever spread?
This virus is endemic, that is, it is frequently found in the tropical areas of Africa, Central America and South America. This disease has two transmission cycles, the jungle cycle and the urban cycle.
1. Jungle cycle: in this cycle the vectors are species of mosquitoes that we usually get in jungle areas, in Central and South America the main vector is Haemagogus and Sabethes.
2. Urban cycle: in this case, yellow fever is transmitted by mosquitoes that have domestic characteristics and are generally found in urban and inhabited regions. The main vector in this transmission cycle is Aedes aegypti, the same vector that transmits Dengue, Zika and Chikungunya viruses.
It is a mosquito that develops and reproduces in containers that can store water, such as tanks, flowerpots and containers that can be found outside of homes such as waste, bottles, cans, plastic containers, etc. Even mosquito eggs can withstand periods of drought of more than a year, so the ideal is to eliminate likely breeding sites and clean containers that are out in the open.
In general, the yellow fever epidemics that have arisen around the world are due to the introduction of infected mosquitoes in large populations, where most of the inhabitants do not have immunity since they have not been vaccinated, it occurs in countries that are are under development and is directly related to the socioeconomic conditions of said population.
However, there are effective prevention measures that would allow to control the problem such as vaccination, vector control (mosquitoes), and timely diagnosis.
Symptoms and signs
The symptoms and signs of this pathology are usually highly variable, in some cases it can become asymptomatic or have mild manifestations, while in other cases the symptoms can be severe, causing hemorrhagic fever and the mortality rate in these cases usually reaches up to 50%.
General symptoms that occur during yellow fever virus infection:
· Jaundice (yellowing of skin and mucous membranes)
· Muscle pains
How the disease evolves
The evolution of the disease goes through three characteristic periods:
· Infection: it is also known as the viremic phase, since the patient is a source of infection. It appears 3 to 6 days after the mosquito bite, it corresponds to the beginning of the appearance of symptoms, which is usually torpid or spontaneous. The fever is high, usually greater than 39 degrees Celsius, chills, headache, nausea, general malaise, muscle aches and Faget's sign which refers to a decrease in heart rate with an increase in temperature.
· Remission: this period lasts from 1 to 2 days, and corresponds to the disappearance of the virus. The symptoms begin to disappear and many of the patients begin to improve, this process usually lasts between 2 and 4 weeks. Although this does not happen in all patients, many of them suffer a relapse, where the symptoms appear again and in a much stronger way, giving rise to the third period of the disease.
· Intoxication: in this stage the symptoms and signs are much more serious, the patient has jaundice, severe abdominal pain, bleeding from the nose, gums and rectum. At this time the liver and kidneys begin to fail so the patient will urinate very little or In very severe cases there may be heart and brain involvement.
There is no specific treatment for this infection, only symptomatic treatment, so absolute rest, use of a mosquito net, administration of paracetamol or acetaminophen should be indicated when the patient has fever and pain, omit any other analgesic or anti-inflammatory that may contribute to the reduction of platelets and therefore increases the risk of bleeding, the patient must be evaluated daily to detect possible complications.
It is important to educate the patient and family members. Mosquito bites should be avoided for at least the first 5 days of the illness, since the patient is a reservoir for the virus and can cause its spread. Possible complications and warning signs (bleeding, jaundice, decreased amount of urine) should also be indicated.
Patients with severe symptoms are hospitalized as they need advanced therapy that includes provision of fluids, drugs, oxygen, and monitoring of each organ and system.
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