Yellow fever is a well-known and at the same time dangerous tropical disease. Similar to malaria, it is transmitted by mosquitoes. Yellow fever is most common in Africa, Central America and South America. Since the symptoms of yellow fever are very similar to those of a normal flu or cold, the disease is often only recognized and treated at a late stage. Anyone traveling to countries at risk should therefore obtain information about vaccination from the relevant tropical institute.
What is yellow fever?
Yellow fever is a viral infection that occurs in the tropical regions of Africa and South America. The yellow fever virus belongs to the Flavi viruses and is closely related to, for example, the dengue virus and the causative agent of hepatitis-C. The first symptoms of yellow fever are chills and fever, and may also include a slowed pulse. Nausea and vomiting, usually with bloody components, and a general tendency to bleed due to reduced blood clotting often complicate yellow fever illness. The viral infection can also lead to jaundice in severe cases. Yellow fever viruses are distributed in 2 variations. Urban yellow fever is a major problem in urban regions because it causes regular epidemics. Sylvatic yellow fever or jungle fever is the typical manifestation in rural areas.
Causes
Infection with yellow fever occurs through a mosquito bite, similar to malaria. The Egyptian tiger mosquito (Aedes aegypti) is the main vector of yellow fever and is therefore also called the yellow fever mosquito. However, other mosquito species are also thought to be involved. Other ways of infection of yellow fever except the bite of the blood-sucking insects are not known. Once the yellow fever viruses have entered the body, they first attack the lymph nodes. Once they have multiplied there, the bloodstream carries them to other organs. The heart, liver, brain and bone marrow are now the targets of the viruses. The pathogens multiply in the tissue cells, causing the infected body cells to die. This leads to severe tissue damage, which is manifested by bleeding in the digestive tract. Viral infection of the heart muscle can have such serious consequences that cardiac arrest is possible in the course of yellow fever. Liver damage as a result of jaundice also poses a life-threatening risk to the patient. Death often occurs because multiple organs fail simultaneously.
Symptoms, complaints, and signs
Yellow fever is characterized by both a mild and a severe course. More than 85 percent experience the mild form of progression with flu-like symptoms such as fever, chills, aching limbs, muscle aches, headache, and nausea and vomiting. These 85 percent of mild sufferers usually recover completely. However, the remaining 15 percent of patients are severely ill and show other symptoms in addition to the usual flu-like symptoms. Thus, the additional symptoms are manifested by diarrhea, severe thirst, overheated skin, vomiting of bile, mild jaundice, bad breath, cessation of urine production, and bleeding in the palate. Afterwards, the symptoms decrease in these patients as well. In some patients, the healing process now begins. However, there are also those affected who have to go through another very severe phase of the disease, which often ends fatally. After a phase of relative calm, they experience increased internal bleeding. This results in such symptoms as coffee-ground-like vomiting, tarry stools or bloody stools. The increased bleeding tendency also leads to frequent bleeding of the skin and mucous membranes. Furthermore, a tremendous loss of fluid occurs, which in turn can cause a state of shock. At the same time, the liver often fails, which is indicated by severe jaundice. Kidney failure and neurological deficits are also common. Without intensive treatment, death occurs no later than the 15th day of illness.
Course
Infection with yellow fever virus goes unnoticed for several days. During this so-called “incubation period”, the virus multiplies until after about a week the inflammation breaks out. However, fever up to 40° C with chills and stomach upsets often subside again. Then the yellow fever is survived unharmed and a lifelong insensitivity (“immunity”) against the yellow fever viruses is the result.In more than one tenth of all cases of yellow fever, a complication occurs after the initial mild course. This “toxic phase” of yellow fever is characterized by jaundice and vomiting of blood. Half of all patients who reach the second stage of yellow fever do not survive the infection.
Complications
In many cases, yellow fever heals without major complications. However, if the infectious disease is treated too late or inadequately, the fever can spread to the brain and cause inflammation of the meninges (meningitis). In the further course, other vital organs may fail and the patient falls into a coma. Accompanying liver-kidney failure, massive hemorrhage can occur, leading to death within ten to fourteen days if left untreated. Other possible complications of yellow fever include cardiovascular disorders and hematemesis. Depending on the patient’s constitution, chronic fatigue or circulatory collapse can sometimes occur, which in turn has physical and psychological effects. As a rule, no complications occur during the treatment of yellow fever. Only fever-reducing medications and the individual home remedies can lead to problems in the case of possible pre-existing conditions or allergies. Vaccination against yellow fever initially leads to redness, swelling and slight pain. One in ten patients also suffers from flu-like symptoms such as fever and joint pain. Rarely, yellow fever vaccination can cause hypersensitivity reactions such as hives or swelling of the mucous membranes in the throat, or even lead to yellow fever infection of the internal organs.
When should you see a doctor?
If various symptoms of illness indicate yellow fever, a doctor should always be consulted immediately. In case of severe diarrhea and problems with urination after a vacation trip to the tropics, the next route should be to a hospital. It is also important that headaches, aching limbs, chills, and fever be examined by a doctor as a precaution. People with immunodeficiency, the elderly, pregnant women and children, or those with cardiovascular problems and thyroid disease should see a specialist even if signs are mild. After a previous yellow fever illness, affected people are usually immune to re-infection, but they should still be examined to be sure. In case of severe circulatory problems or strikingly high fever, an emergency doctor must be called immediately. If the affected person falls into a coma during this time, first aid must be administered until the doctor arrives. The doctor must be informed about how the circulatory collapse occurred.
Treatment and therapy
There is no causative therapy for yellow fever. All drugs that inhibit viral replication showed no effect in yellow fever. Thus, the physician must limit himself to combating the life-threatening symptoms. For this purpose, the patient is transferred to the hospital and monitored there with intensive care. Only in the hospital can the patient be guaranteed an adequate supply of fluids with infusions. The physician must compensate for excessive blood loss with blood transfusions. Because the therapeutic treatment options for yellow fever are limited, great importance is attached to preventive measures. First and foremost, vaccination is the best protection against an outbreak of yellow fever. In this “active immunization”, the physician injects the patient with a solution containing attenuated yellow fever viruses that do not cause illness. However, the body responds by producing specific defenses called “antibodies.” Vaccination protection against yellow fever lasts for about 10 years. In addition to this very effective measure, everyone traveling to the danger zones should protect themselves from mosquito bites if possible. Mosquito control is left to the health ministries of the affected countries.
Outlook and prognosis
A specific therapy against yellow fever is not yet available. Only the symptoms are treated. For a large proportion of infected persons, the prognosis is positive. The symptoms subside after a few days. Consequential damages do not remain. However, treatment should not be missed. A severe course develops in about 15% of those affected. About half of those affected do not survive yellow fever. Fever and pain are treated with medication.The patient is isolated so that the disease is not spread by renewed mosquito bites. If yellow fever takes a more severe course, meningitis can break out. If vital organs fail, the affected person falls into a coma. Failure of liver or kidney function is particularly common. Damage to the kidney can be detected by protein levels in the urine. In the liver, the bilirubin level is significantly elevated. Those who survive infection with yellow fever no longer show any symptoms because sufficient antibodies have been produced. It is assumed that there is lifelong immunity to the infection. In order to avoid complications, vaccination should be carried out. In some countries, this vaccination is even mandatory.
Follow-up
Options for aftercare are usually very limited for yellow fever. First and foremost, the disease must be treated first, although a complete cure is not always possible. In some cases, this also limits the life expectancy of the affected person if the yellow fever is detected relatively late. To prevent yellow fever, an appropriate vaccination should be given before traveling to the affected countries. The patient is dependent on purely symptomatic treatment for this fever. It must be noted that the affected person must take plenty of fluids to compensate for the loss. Likewise, transfusions of blood are necessary in some cases to fully treat the condition. The patient should rest as much as possible and avoid exertion or stressful activities. In general, bed rest has a very positive effect on recovery. Likewise, the body must be protected from other diseases or infections so as not to put unnecessary strain on the immune system. After vaccination, protection against yellow fever usually lasts for ten years. After this time, the vaccination should be refreshed.
What you can do yourself
If yellow fever is suspected, a medical clarification is necessary in any case. Once diagnosed, the various symptoms can be treated independently under medical supervision. In the first place is the balance of fluids and minerals. Through vomiting and diarrhea, the organism loses various nutrients, which must be returned to the body through a wholesome diet and nutritional supplements. Accompanying bed rest and sparing apply. Light medicines and various home remedies (willow bark extract, peppermint oil, cinnamon, etc.) help against the headache, while the fever can be relieved by cooling compresses or cold calf wraps. Dietary measures help against nausea and vomiting – especially sparing food and herbal teas are indicated. If the yellow fever enters the second phase, a hospital must be visited. Due to the severity of the symptoms, sleep and rest are recommended, as well as drug treatment. If the course is positive, the patient can leave the hospital after one to two weeks. The return to everyday life should take place slowly and under constant observation by a trusted person, as there is an acute risk of accidents due to the lasting coordination disorders. In addition, follow-up with a physician should be done to ensure that yellow fever is completely overcome.
