yellow fever

Yellow fever: description

Yellow fever is caused by the yellow fever virus. It is caused by the bite of infected yellow fever mosquitoes (Egyptian tiger mosquito, Aedes aegypti) transferred to humans. The disease only occurs permanently in certain regions of the world. These are called yellow fever endemic areas. They are located in tropical Africa and South America. Travelers with the appropriate destination should be sure to check in advance if a yellow fever vaccine is required. Asia, Australia, Europe and Oceania are currently considered yellow fever free.

Tropical physicians annually report about 200,000 yellow fever diseases and 30,000 deaths worldwide. About 90 percent of them are in Africa. Every suspicion, every illness and every death by yellow fever is notifiable. Nevertheless, the World Health Organization (WHO) estimates that there is a high level of unreported cases. This means that even more people get yellow fever, but these cases either not reported or not recognized as such.

There are two types of yellow fever: the Jungle Yellow Fever and the City Yellow Fever, The naming depends on where and by whom you are infected. Originally, the reservoir is the pathogen, that is, the animals in which the viruses normally reside and multiply, living in the jungle monkeys. Mosquitoes transfer the viruses from one monkey to the other there. When people are in the jungle, they run the risk of being stung and infected as well. Due to the origin of this species is called jungle yellow fever. It mainly affects young men, such as forest workers.

In contrast, the city yellow fever. In this case, a person suffering from yellow fever stays with other people. If the carrier mosquitoes are present, there is a danger of an epidemic. That is, via the mosquitoes, the yellow fever spreads from person to person in a specific region.

Yellow fever: symptoms

The yellow fever symptoms develop about three to six days after infection. This time will be incubation period called. Yellow fever has a mild course in about 85 percent of cases, which roughly corresponds to the symptoms of a flu infection. After just a few days, those affected feel better again and recovery occurs. In the remaining 15 percent of the cases, the disease is very difficult. In particular, an organ failure of liver and kidney occurs. In the further course it can come in the context of a multi-organ failure to bleeding all over the body. For this reason, the yellow fever is counted among the group of hemorrhagic fevers (as well as Ebola, Lassa fever, etc.). About 50 to 60 percent of people with this severe form die.

Attention! Yellow fever is not to be confused with jaundice. Jaundice is colloquially a yellowing (icterus) of the skin and eyes due to a disturbed bile outflow, for example in hepatitis (hepatitis) or cholangitis (bile duct inflammation). Although jaundice can occur with yellow fever, it is only one of the possible symptoms.

Easy course (about 85 percent)

For about three to four days, patients complain of flu-like symptoms. These include:

• Fever up to 40 ° C
• chills
• a headache
• body aches
• Muscle aches
• nausea
• Vomit

Severe history (about 15 percent)

A severe course can be seen in many cases two disease phases, In the first phase, in addition to the symptoms of a mild course, the following symptoms of yellow fever may develop:

• Vomiting of bile
• diarrhea
• Strong thirst and overheated skin on the face and trunk (“red stage”)
• Unpleasant bad breath
• Mild jaundice (jaundice)
• Squeezed urine production
• palate bleeding

This is followed by an interval of one to two days during which the yellow fever symptoms noticeably decrease and the patient sleeps a lot (“period of calm”). In some patients, the disease now comes to a standstill. Others go into the second phase of yellow fever. The main focus is on damage to the liver and kidneys (hepatorenal syndrome, “yellow stage”). This can lead to the following symptoms:

• Coffee grounds vomiting, tarrene (melena) or bloody diarrhea
• Skin and mucous membrane bleeding
• Yellowing of the skin (jaundice) due to acute liver failure
• High blood and fluid loss can cause shock. The patients have too low a blood pressure. The pulse is often also low in yellow fever (bradycardia).
• Acute renal failure with greatly reduced or absent urine production (oliguria, anuria)
• Lack of detoxification by the liver and kidneys leads to accumulation of toxic metabolic products in the blood (toxemia).
• Neurological abnormalities such as speech disorders, apathy, convulsions and movement disorders
• Death on the 6th to 7th day due to renal failure and circulatory insufficiency or heart failure on the 10th to 15th day of illness.

Yellow fever: causes and risk factors

The yellow fever is from the Yellow fever virus caused. The virus belongs as well as the causative agent of tick-borne encephalitis (TBE) or dengue fever to the genus of flaviviruses, The yellow fever virus is transmitted from one host to another by the bite of the yellow fever mosquito. A host is an organism whose cells need the virus to multiply. The yellow fever virus is used by humans and monkeys as hosts. The monkeys are the natural reservoir of the virus. For many ape species, especially the African, infection with the yellow fever virus is harmless. Only when a mosquito picks up the virus during the blood meal of a monkey and then stings a person, the virus enters the human.

If a person is infected, mosquitoes can take the virus from him and infect other people. This can trigger epidemics. A direct infection from person to person, that is without the mosquito as transmitter, is not possible, Therefore, there is only a risk of infection if the insects are present.

Spread of the yellow fever virus in the body

When the yellow fever virus enters the blood via the mosquito bite, it initially increases in the lymph nodes. It then spreads through the blood throughout the body. The most important target organ of the yellow fever virus is the liver, which is particularly damaged in the disease. This also explains the frequent yellowing of the skin and eyes (jaundice). In addition, the virus reaches various other organs such as the kidneys, the spleen, the bone marrow and the muscles. The body tries to defend itself against the virus and produces certain messenger substances (cytokines). However, uncontrolled production and release may occur during the process, severely damaging one’s own body and causing multiple organ failure.

Yellow fever: examinations and diagnosis

Leading the way to diagnosis Yellow fever are the travel history (travel history), fever, bleeding and a yellowing of the skin. If your doctor suspects yellow fever, he usually asks for yours travel history, This includes among others the following questions:

• Have you been in another country lately? If so, in which one?
• When exactly were you there?
• What did you do there?

In addition, he asks your symptoms, for example:

• Do you have pain?
• Do you have fever?
• Is your chair dark colored?
• Since when are you having those complaints?

In addition, your doctor will examine you, for example by palpating your abdomen, to rule out enlargement of the liver or spleen. In addition, he takes blood off and has it examined. Typical changes such as elevated liver values, accumulation of toxic metabolic products and possibly coagulation disorders may occur.

virus detection

There are two different methods by which a yellow fever infection can be detected. In the first ten days of the disease may be in a so-called Polymerase chain reaction (PCR) the genetic material of the yellow fever virus in the blood are detected. About the fifth day of the disease, the patient has antibody formed against the yellow fever virus. These can also be visualized in the blood (serological examination).

Sometimes it is difficult to diagnose yellow fever. This is mainly due to the unspecific, flu-like symptoms at the beginning of the disease. The bleeding and organ damage of the second phase may also appear in other diseases. To distinguish from yellow fever include: malaria, typhoid, Ebola or Lassa fever and hepatitis B or D.

Yellow fever: treatment

There is currently no specific therapy for yellow fever. The disease can therefore only symptomatic be treated. This means treating only the signs of the disease. The causative yellow fever virus, however, you can not fight. Even so-called antiviral drugs do not help here.

Symptomatic treatment

First and foremost, the fluid losses are compensated with infusions, the fever with fever medication such as paracetamol and possibly supports breathing. In addition, the weakening of the organism can lead to additional bacterial infections. These are then treated with antibiotics.

Especially if the disease passes into the second phase in a severe case, many patients on the intensive care unit are cared for. In a yellow fever endemic area where the Egyptian tiger mosquito is present, the patient must be isolated. In this quarantine he can not be stung by mosquitoes, so they can not transfer the virus to other people.

Yellow fever: vaccination

How to prevent yellow fever with a vaccine, read in the article yellow fever vaccination.

Yellow fever: disease course and prognosis

The yellow fever runs in the majority of cases (about 85 percent) mild and is over after a few days. In some cases (about 15 percent), however, an extremely severe, biphasic course may develop, killing more than half of the cases. Those who survive the disease usually have no symptoms. It is believed that the patient is then immune to yellow fever throughout life due to the antibodies.

Prevent yellow fever

Because there is no specific treatment and yellow fever is potentially life-threatening, vaccination is very important. It is mandatory for entry and exit (and possibly transit) to some countries in Africa and South America. Only if a large part of the population in a region is vaccinated against yellow fever, can an epidemic spread be prevented.

In addition to the vaccination should also be placed on the mosquito repellent. It should be noted that the yellow fever mosquito is both active at night and day. Therefore, a permanent protection is necessary. During the day, this is achieved through special, tropically suitable mosquito repellents (“repellents”) and long, light-colored clothing. At night, an impregnated mosquito net protects against the bloodsuckers. Preventing mosquito bites contributes significantly yellow fever and other tropical diseases (malaria, dengue).