What is Yellow Fever?
Yellow fever is a viral condition that is transmitted by mosquitoes infected with the yellow fever virus (YVF).
This disease is common to regions with tropical climates, such as South America and Africa. Areas that have a high number of mosquitoes are also more prone to yellow fever epidemics.
Yellow fever is usually an acute condition, with symptoms resolving within a week of onset. Any individual not vaccinated against yellow fever can contract it. (1)
The virus responsible for yellow fever is classified as an arbovirus. It belongs to the genus flavivirus, which includes other mosquito and tick-borne illnesses. (2)
Two different species of mosquito are capable of spreading yellow fever: haemagogus and aedes. Infections from the virus tend to increase during hotter months, when mosquitoes are more active. (3)
Transmission can occur in one of three environmental settings. Sylvatic yellow fever, also known as jungle yellow fever, is transmitted within tropical rainforests.
People visiting these areas can get bitten by a mosquito infected with the virus.
Intermediate yellow fever is transmitted by semi-domestic mosquitoes which carry the virus. This means they breed near households and in wild areas.
These mosquitoes then infect people. This form of transmission is most common in African countries, and can affect numerous villages in one region simultaneously.
Urban yellow fever is unique to densely populated areas with excessive numbers of mosquitoes from the aedes species.
If the majority of the population is unvaccinated, infected mosquitoes can spread yellow fever rapidly. (4)
Aside from getting vaccinated, the only other method of preventing yellow fever is to avoid being bitten by mosquitoes.
This can be a difficult feat, as mosquito bites can penetrate very light clothing. You must wear protective clothing and use mosquito repellents on any exposed skin.
Mosquitoes are more active during the hours of dusk and dawn, although you can be bitten at any time.
Mosquito nets should be used if you do not have access to an enclosed, air conditioned room. It is also important to empty any receptacles that accumulate water.
This is because buckets, pots, and other containers with standing water are ideal breeding habitats for mosquitoes. (5)
Infections from the virus tend to increase during hotter months, when mosquitoes are more active. (6)
Symptoms of this viral infection can include one or more of the following: (7)
A typical sign of this viral infection is the onset of a fever. If infected, you may develop a temperature of over 38 degrees celsius.
A headache can be caused by a variety of conditions and stimuli. However, if your headache is accompanied by other warning symptoms it may be yellow fever.
You may experience pain in your muscles as a result of yellow fever. This symptom can also manifest as an aching in your back.
Nausea and Vomiting
A common symptom of yellow fever is nausea that may also be accompanied by vomiting.
If your gastrointestinal tract is bleeding as a result of the virus, this blood can appear in your vomit and color it black. (8)
Loss of Appetite
Aside from feeling generally unwell, you may also suffer a loss of appetite.
If your condition grows more severe, jaundice can develop. This involves a yellowing of the eyes and skin.
Jaundice is often a warning signal of liver dysfunction or damage. This symptom is responsible for the name of the yellow fever viral infection itself. (9)
Another sign of a serious yellow fever infection is bleeding. You can bleed from your nose, mouth and eyelids.
Your gastrointestinal tract may also bleed. This blood can then appear in your feces or vomit. (11)
Yellow fever progresses through three distinct stages. However, not all infected individuals will pass through all of them.
The stages of yellow fever can develop as follows: (12)
If you have been bitten by an infected mosquito, the virus will incubate in your body.
This incubation period can last from three to six days.
This stage is known as infection. You may begin experiencing typical symptoms such as fever, headache, nausea and vomiting.
These symptoms will typically last for a period of several days.
The second stage for most individuals infected with the virus is remission. Symptoms begin to abate, and you will start to recover.
Stage 3 is defined as intoxication. Certain infected people may suddenly grow worse in the space of 24 hours.
If you enter this stage, symptoms usually return and intensify. Vital organs such as your kidneys and liver can be affected by the virus and you may suffer excessive bleeding.
The intoxication (or toxic) phase is fatal for approximately half of all individuals who enter it.
These people die from complications caused by the virus within a period of one week to 10 days. (13)
Yellow fever is typically diagnosed through a review of your medical and travel history, followed by a blood test.
If you are residing in a region which is non-endemic (i.e. without a prevalence of yellow fever) and present with symptoms, your doctor will review your travel history.
This will allow your doctor to assess your likelihood of infection and rule out other potential causes.
To confirm a diagnosis of yellow fever, a blood sample will be analyzed for virus-specific antibodies.
If you live in an area that does have yellow fever outbreaks (e.g. certain parts of Africa) this blood antibody test will be performed directly. (14)
Yellow fever cannot be transmitted between individuals, only from the bite of a contaminated mosquito.
However, an infected person can transmit the virus to a mosquito. For this reason, if yellow fever is suspected in a non-endemic area you may be isolated.
There is no specific treatment for yellow fever itself, such as an antiviral drug. Rather, doctors aim to reduce and manage symptoms as your body fights the virus. (15)
Depending on your condition, you may receive one or more of the following recommendations or treatments:
As yellow fever is usually a self-limiting condition, it is advisable to rest while your symptoms are active.
It is important to avoid dehydration. Drink as many fluids as you can, preferably water. (16)
To reduce muscle aches, headache and fever your doctor may recommend taking an over the counter drug such as paracetamol. (17)
It is not recommended to take non-steroidal anti inflammatory drugs (NSAIDs) such as aspirin. These medications may increase your risk of excessive bleeding. (18)
If you have a bacterial infection, it may exacerbate the yellow fever. Any infections should be promptly treated with antibiotics to speed up your recovery.
If your symptoms grow severe (e.g. organ failure) you will have to be hospitalized. This will enable doctors to monitor and treat any issues for the best possible outcome. (19)
What is yellow fever? Yellow fever is a type of viral infection which is usually acute.
What are the signs of yellow fever? Signs of yellow fever can include headache, fever, muscle pain, loss of appetite, nausea and vomiting. Other symptoms include jaundice, dark urine and bleeding.
How do you develop yellow fever? You can develop yellow fever as a result of being bitten by a mosquito infected with the yellow fever virus (YFV).
How are you diagnosed for yellow fever? Your doctor will review your medical and travel history. A blood test can reveal the presence of yellow fever virus antibodies.
What is the best treatment for yellow fever? As there is no specific drug to treat the virus, treatment involves managing symptoms. Your doctor will recommend bed rest, painkillers, staying hydrated and antibiotics to treat any other infections you may have. Hospitalization may be required in more severe cases.
What are the complications of yellow fever? Complications can include kidney or liver failure, coma and bacterial infections. Disseminated intravascular coagulation (DIC), a type of blood clotting disorder, can also occur. (20)
Is yellow fever considered a disability? No, yellow fever does meet the criteria of a disability. The condition is not chronic and does not impair your ability to work long term. (21)
Is yellow fever life threatening? Yes, yellow fever can be life threatening. Up to 50 percent of individuals who develop the severe form of the disease are at risk of death. (22)
Yellow fever can be a potentially fatal condition. Fortunately, this viral disease is entirely preventable.
The vaccination against yellow fever will provide you with immunity to the virus for the rest of your life. This vaccine is effective in 99 percent of people, and works within 30 days of injection.
If you are traveling to a region where yellow fever is prevalent, you may be required to get vaccinated.
If you suspect you are infected with yellow fever, seek immediate medical attention.
Although most infected individuals have a good chance of recovery, untreated complications (such as organ failure, for example) can be fatal. (23)