Complete Guide: All You Need to Know About Yellow Fever

Complete Guide: All You Need to Know About Yellow Fever

The identification of cases of yellow fever in Brazil is generating many doubts in the population and bringing concerns about the  health of their families . The severity of the disease makes it essential to understand its main aspects.

To clarify this issue, we have prepared this guide with everything you need to know about this disease. We will explain what it is, ways of transmission, prevention, diagnosis and treatment, as well as talk about vaccination and clarify the main myths and truths on the subject.

Are you interested? So read on and be informed!

What is yellow fever and how it is transmitted?

It is a serious infectious disease caused by a virus. It usually causes high fever and jaundice – a disorder of the body that leaves the body with a yellow tint – which is why it has that name.

The vectors of this disease are the mosquitoes  Aedes aegypti  (responsible for the transmission of dengue, chikungunya and zika ) Sabethes  and  Haemagogus that can infect humans and some primates, such as monkeys.

This disease is most common between the months of December and May. Summer is known to increase the population of mosquito vectors, due to the large amount of rainfall, allowing greater movement of the virus.

In 2017 it was remarkable the occurrence of  yellow fever outbreak in the first half  – was recorded 777 confirmed cases and 261 deaths. However, after 90 days without new cases notifications, the outbreak was declared ended in September of that year.

However, with the identification of new cases of infected monkeys, it became clear that there is a new cycle of the disease, which is why the warning and prevention and vaccination campaigns remain heavily publicized, particularly in the areas and risk groups.

transmission cycles

The disease is classified into two different cycles, according to broadcast area:

  • urban cycle: it occurs in cities, transmitted by the  Aedes aegypti ;
  • sylvatic cycle: occurs in rural areas, transmitted  Sabethes  and  Haemagogus.

In both cases the virus and the clinical course are the same. According to information from the  Ministry of Health , the last urban cycle that occurred in Brazil it was in 1942 and all subsequent – including detected from July 2017 – were the sylvatic cycle.

In such cases, the transmission takes place as follows: a female mosquito bites an infected host, acquiring the virus that circulate in your bloodstream to settle in the salivary glands.

After a few days, the mosquito can transmit the disease already. Therefore, when biting a human or monkey it infects a new host, continuing the cycle.

It is worth mentioning that you can not catch the disease by coming into contact with other infected people or animals: the only way of transmission are mosquito bites that are carriers of the virus.

Risk areas

The risk areas are those where there are more chances of infection by the virus, taking into account the specific conditions of each site, and there are around the world. Currently, they are located in Africa, Central America and South America, totaling 47 countries with outbreaks.

In Africa, the greatest risk is in the sub-Saharan region – south of the Sahara Desert, such as Angola, Congo and Nigeria. In Central America, the areas of greatest risk are in Trinidad island, Trinidad and Tobago, and Panama.

In South America, besides Brazil, are also risk areas considered the following countries:

  • Bolivia;
  • Colombia;
  • Ecuador;
  • Guiana;
  • French Guiana;
  • Paraguay
  • Peru;
  • Suriname;
  • Venezuela.

risk areas in Brazil

In Brazil, the list updated by the WHO on  16 January 2018 , considered risk areas states north, Midwest – including the Federal District – south and southeast of the country, besides Bahia, Maranhão and Piauí, in the Northeast.

Moreover, not all cities of these states are at high risk of contamination. So to be sure about the places that require vaccination is essential to seek information with the health department of your state or county.

Interference of the monkeys in the cycles of disease

Despite being recurring news of mistreatment and deaths of monkeys, caused by people who seek to fight the disease, there is no basis for this practice.

Yellow fever is a zoonosis, that is, affects animals and humans, but transmission does not occur between infected. Aiming to inform the public about it, the Ministry of Health launched the campaign “The fault is not the monkey.”

Besides he is not the cause of the disease or transmitting directly to humans, monkeys have an important role to alert the authorities about the possibility of incidence of the virus in a particular region.

What to do when faced with a monkey?

In any situation, do not get too close or harm the animals: respect your space and its habitat. If he is healthy, limit yourself to take pictures or spot him with distance.

However, if you encounter an animal that appears infected or dead, immediately notify the health service of the municipality or state the number 136. After receiving the information, the agency will take some actions, such as:

  • attempting to collect a sample for laboratory analysis;
  • Check for other dead or infected animals.

These precautions are necessary to identify whether it is a case of yellow fever, it was an isolated occurrence or if other monkeys were also infected. If so, the health service will initiate preventive measures, so that the disease does not reach the population.

What are the symptoms of the disease?

Despite the severity of yellow fever in some situations the infected person does not get to experience symptoms or features of mild form – as in a  virus  – not developing the disease. But who develops usually has these signs of sudden way.

The disease involves two phases: acute and toxic. Here are the symptoms of each:

Symptoms of acute phase

The acute phase takes place at the beginning of the infection, and the early stage of the disease, with a few days’ duration. The symptoms are:

  • chills;
  • tiredness;
  • headache ;
  • muscle pain, especially in the back and knees;
  • fever;
  • nausea;
  • loss of appetite;
  • face, red eyes or tongue.
  • sensitivity to light;
  • dizziness;
  • vomiting.

In general, the recovery of this phase occurs in up to four days, but in some situations the person develops severe symptoms, entering the toxic phase of the disease.

Symptoms of toxic phase

The toxic phase is not developed by those infected. Considered the most severe form of the disease, it brings life-threatening for the patient.

The first signs usually manifest that phase about two days after remission of the acute phase and a period of well-being of the patient. The main symptoms are:

  • severe tiredness;
  • brain dysfunction, such as delirium, seizures and coma;
  • abdominal pain;
  • recurrent fever;
  • slow heart rate;
  • internal bleeding and clotting;
  • liver failure (jaundice);
  • renal insufficiency;
  • bleeding from the nose, eyes or mouth;
  • blood in vomit or stools;
  • dark urine;
  • vomiting.

In more severe cases, it can happen multiple organ failure due to lack of blood circulation caused by blood clots and bleeding. The main organs affected in these cases are the heart, liver and kidneys.

The hypovolemic shock is another serious complication, also caused by lack of circulation. The low volume of blood can cause the heart to accelerate, causing an overload. This condition is extremely severe, with large mortality rates, so treatment should be immediate.

Therefore, after the end of the acute phase, it is essential to remain alert to identify any symptoms of toxic phase. Its mortality rate is high and the sooner the patient to seek medical help, the greater the chances of cure.


Diagnosing yellow fever is not a simple task. The initial symptoms are similar to other diseases such as dengue hemorrhagic fever, hepatitis, leptospirosis and malaria.

However, in times of outbreak doctors usually identify suspects more quickly, questioning the patient about the travel history to see if he was in any risk area, in addition to blood tests.

With the results of blood tests, doctors look for signs of infection, such as the reduction of white blood cells. Depending on the case they may also be obtained from other tests such as ELISA serology and polymerase chain reaction.

How is the treatment of yellow fever?

There is no specific drug to fight the virus of yellow fever. So the treatments are focused on easing the symptoms or the admission of the patient to hospital monitoring, depending on the outcome of clinical evaluation.

During treatment the patient should be at rest and drink plenty of fluids to prevent dehydration which may be caused by vomiting. Furthermore, it should properly follow medical indications, especially in relation to drugs.

In more extreme cases, they can be recommended the following interventions:

intravenous Solution

In cases of dehydration when vomiting is recurrent and do not allow the patient to rehydrate, hospitalization for intravenous treatment is essential.


In cases of renal failure, it is necessary to refer the patient to dialysis, which is a procedure that replaces kidney function, filtering the blood by machines to prevent the accumulation of toxins.

Blood transfusion

In case of bleeding may be necessary that the patient receive transfusions of blood or plasma to replace blood proteins and to improve coagulation.

Remember also that those who have had the disease, is immunized and has no risk of being infected again, given that the body will already have the antibodies to fight the virus.

You can prevent yellow fever?

The concern with this disease is common, especially during outbreaks, however, and is curable, there are also ways to prevent. The main thing is to get the vaccine, which will ensure their immunization to the virus.

However, there are other tips that can help combat the spread of the virus, and similar to those of dengue prevention. Meet:

Avoid their proliferation

Mosquitoes use the still water spots to play, so, take precautions, such as:

  • do not leave containers and tires accumulating rainwater;
  • put sand in potted plants;
  • Clean roof gutters.

That way, you help reduce the focus of mosquito vectors.

Protect yourself from mosquitoes

Whereas the yellow fever cycles that have been identified in recent years are of wild origin, it is more difficult to control the proliferation of mosquitoes, in view of their habitat (forests and rural areas).

However, you can take steps to avoid mosquito bites. Some precautions you should take are:

  • use mosquito nets and screens to prevent mosquitoes from entering home;
  • use repellents (if using sunscreen, apply it first);
  • avoid leaving the exposed skin, give preference to long, light-colored clothes.

Remember that these measures do not replace vaccination, which is the most effective way to prevent the disease, according to the World Health Organization (WHO).

What to know about the yellow fever vaccine?

Vaccines are made with live attenuated viruses, administered by injection. After vaccination, the person will develop the antibodies needed to combat the virus, becoming immune to infection.

As the largest form of prevention, we separate the main information about it. Look:

People who should be vaccinated

Everyone should be vaccinated, children or adults, who live in risk areas or in their vicinity, as the  vaccination schedule .

Also, people who are traveling to these areas, both inside and outside Brazil, should be vaccinated 10 days in advance, so that the body has time to produce antibodies.

People who should not get the vaccine

Although it is necessary to prevent the vaccine should not be applied in less than 6 months, they are more vulnerable and therefore more likely to suffer complications dosing.

Furthermore, it should be avoided in  pregnant  and nursing women, and immunocompromised persons allergic to certain substances in the vaccine, such as egg protein, beef gelatin and erythromycin.

However, in the case of hazardous areas dwellers or people who need to travel to one of these regions it is important to consult a doctor. The professional can verify risks of the vaccine and the ability to implement measures to mitigate them.

the need to strengthen

The standard dose of the vaccine protects a person for life – the recommendation on strengthening every 10 years has been withdrawn by the WHO in 2014.  Brazil has adopted this recommendation  in early 2017, so if you have taken the vaccine , no need to take a new dose.

fractional vaccine

The fractional vaccines have generated enough questions, especially as to its effectiveness. However, there is no reason for concern: they ensure immunization to patients.

This is an emergency measure, it is made to apply a lower dose than the traditional, to increase the number of people vaccinated. In such cases, after eight years the person will need to be vaccinated again to keep immunized.

Adverse reactions

The yellow fever vaccine can cause some adverse reactions to patients, not being a recurring. Are they:

  • mild headache;
  • muscle aches;
  • pain at the injection site;
  • fatigue;
  • low-grade fever.

If she has any symptoms, it is recommended to seek medical attention to evaluate the case and, if necessary, spend some medication to relieve the symptoms.

international certificate of vaccination or prophylaxis (CIVP)

In addition, some countries require visitors to submit the CIVP as proof of vaccination against yellow fever. The issue of this document is made in the Guidance Centers for Travelers’ Health Anvisa and the units of the Unified Health System (SUS) accredited, free.

Where vaccination is not recommended, the doctor may issue a letter of exemption from the vaccine, which should be done on letterhead and indicate and detail the reasons why the patient had not been vaccinated. In some cases, the immigration authorities may accept the document to release the person entering the country.

Myths and truths about yellow fever

With concerns brought about by the increased incidence of the disease, it is common to hear a lot of information on yellow fever. However, not all are true, which can lead to confusion and even undermine the campaigns and treatments against it.

To clarify the matter, we separate the main myths and truths about this disease. See below:

It is transmitted from person to person

This is a myth. As already explained, this disease is transmitted by the bite of infected mosquitoes. Therefore, contact with infected people does not transmit yellow fever.

Thus, there is no problem in attending crowded places that may have infected people around you – it will not increase the risk of infection.

A monkey can transmit the disease to humans

Another myth. In fact, the monkeys can also be hosts of the disease, like humans. The mosquito can poke a sick animal and, subsequently, transmit the disease to other hosts (humans and apes).

However, contact with these animals is not capable of infecting humans. In addition, they help to identify the incidence of the disease in the region.

repellent pass prevents disease

Partly true. Although it is recommended to use repellents and long clothing to avoid contamination, no measure replaces the vaccine, especially for residents and visitors to endemic regions.

Who do not live and will not travel to risk areas do not need the vaccine

Truth. The Ministry of Health reported that vaccination is directed to people who live or will travel to any area where it is recommended the vaccine.

There are two types of yellow fever

Myth. There are actually two cycles: urban and wild. As explained, in rural areas the virus is transmitted by mosquitoes  Haemagogus  and  Sabethes . Were in the cities it is propagated by  Aegypti Aedes .

The vaccine is not recommended for elderly

It is also a myth. Elderly patients over 60 years old can get the vaccine, but only to undergo an assessment before the procedure.

Pregnant and lactating women should not be vaccinated

Partly true. Vaccination is not recommended for pregnant women, however, the occurrence of outbreaks, epidemics or travel to risk areas, it must be evaluated by the health service to check the risks and benefits of the vaccine to be making the best decision.

Regarding  breastfeeding  there is no seal if the child already has more than 6 months in the case of residence or shift risk areas. In cases of children less than 6 months the vaccine should be avoided.

However, if you can not put off, she should take care to prevent transmission of the vaccine virus, which should be indicated by your doctor.

Take the vaccine several times let the most protected person

Myth! Since the vaccine follow the standards scheme of the National Immunization Program – as with yellow fever – to take it one will be protected, there is no need to be vaccinated before.

Thus, if vaccines are up to date, according to the National Immunization Calendar, it will be protected. Moreover, when taking the vaccine without, you will take the opportunity of someone’s risk group to protect.

People allergic to eggs can not be vaccinated

This information is also a myth. In such cases it is necessary for the person to go through medical evaluation and receive the vaccine in a place that has service conditions for anaphylactic reactions.

Who does treatment with immunosuppressive drugs can be vaccinated

Partly true. For this, they should discontinue use for up to three months depending on the type of medication. The ideal is to ask the doctor, who will pass the correct information and timely basis.

Thus, it is essential to be informed about yellow fever, if properly prevent and seek medical attention before any symptoms to seek a diagnosis and, if necessary, treatment.

Ready! Now that you’ve clarified your questions about yellow fever, how about sharing this article on your social networks? So you inform others about this disease!


Spread the love

No comments.

Leave a Reply