Yellow Fever

It is transmitted through the bite of mosquitoes of the genus Aedes and Haemogogus, which mainly inhabit countries in Africa and areas of northern South America, where the disease is endemic.

Yellow fever is an acute and infectious viral disease that is produced by the virus belonging to the family of the Flaviviridae of the genus Flavivirus amaril . The adjective “yellow” refers to the signs of jaundice that appear in some patients.

It can now be effectively prevented by vaccination. However, it continues to represent a public health problem, causing around thirty thousand deaths a year.

Causes

Currently, yellow fever has a notable incidence in areas such as: Africa, South America and the Caribbean. Most outbreaks occur in people who work in rainforests, which is why it is considered to be an occupational disease. 

Yellow fever is transmitted by the bite of female mosquitoes, mainly of the genus Aedes or Haemagogus, which are abundant in humid areas, around stagnant water.

Two main transmission cycles are known: the jungle and the urban. In addition, in Africa there is also an intermediate cycle

We recommend you read: The 6 best natural remedies to cure mosquito bites

1. Jungle yellow fever

This type is transmitted from monkey to monkey, having as a vector the Aedes africanus mosquito , which lives in central Africa. It also occurs in South America, but due to the bite of Haemagogus mosquitoes . This form of transmission is rare in humans, since it only occurs when, for some reason, they enter the jungle.

2. Urban yellow fever

This is the most common type and is transmitted from person to person, through the bite of the Aedes aegypti mosquito , which abounds in humid areas around stagnant water reservoirs and only bites during the day.

3. Intermediate transmission cycle

This transmission cycle occurs when the yellow fever virus is transmitted from monkey to man and from man to man by the bite of Aedes simpsoni and Aedes bromeliae mosquitoes . They are common in the humid savanna areas of Central and West Africa during the rainy season.

Symptoms

The incubation period for yellow fever lasts between 3 and 6 days until symptoms appear. Its name refers to two of its main symptoms: fever and jaundice (yellowing of the skin). Depending on its development, we can say that the infection goes through three stages:

Stage 1

Most infected patients stay with stage one yellow fever, and since the symptoms are similar to those of a flu syndrome, it is overlooked by many. This phase lasts 3-4 days and may include:

• Muscle and joint pain
• Headache.
• Fever and hot flashes
• Lack of appetite
• Vomiting
• Jaundice.

Stage 2

Patients generally recover after reaching this stage. However, some cases can get worse within 24 hours.

Stage 3

Half of the patients who reach this phase die within 7 to 10 days. If the infection progresses to a higher level of severity, what is known as hemorrhagic fever occurs, compromising the health of the heart, liver and kidney. Symptoms include: jaundice, high fever, seizures, vomiting (of clotted blood), internal bleeding, coma, and delirium.

Diagnosis

The diagnosis of yellow fever is often difficult, especially in the early stages, due to the similarity of its symptoms to flu-like symptoms. The most severe cases are also often mistaken for severe malaria, viral hepatitis, and other flavivirus infections (such as dengue hemorrhagic fever).

It is for this reason that, initially, the health professional will start with some clinical data, questioning the patient about possible trips to endemic areas of the disease, and if they have received the yellow fever vaccine.

The doctor will also suggest selected blood tests, which will be used to detect the virus and determine if there are complications at the liver and kidney level. Tests include a complete hematology, in which a decrease in white blood cells (leukopenia) and an increase in hematocrit due to dehydration can be observed, indicating the presence of yellow fever.

Treatment

Currently there is no specific antiviral treatment to cure yellow fever. This is why, initially, the most effective measure is its prevention through vaccination.

Unvaccinated people who contract the disease can only receive symptomatic treatment, which aims to reduce the severity of symptoms. The use of antipyretics to reduce fever and analgesics to relieve pain is recommended. Aspirin should not be used because of the risk of bleeding.

On the other hand, it is essential that the patient drink plenty of fluids to avoid dehydration. If associated bacterial infections occur, the doctor will suggest antibiotics to treat them.  In case the disease reaches its most advanced stage, treatment includes:

• Blood products for severe bleeding.
• Dialysis for kidney failure.
• Fluids through a vein (intravenous fluids).

If you are thinking of traveling to endemic areas of the disease, or if you live or work in one of them, it is essential to consult your doctor and request a yellow fever vaccine.