Yellow Fever

Yellow fever is typically spread through mosquito bites, with the primary source being the Haemagogus species and Aedes aegypti. The virus is commonly found in tropical and subtropical areas of South America and Africa, where it can be easily transmitted from monkeys to humans through mosquito bites in forested areas.

These mosquitoes are active throughout the day and night and can thrive even in the cleanest water sources near human settlements.

Yellow fever can be transmitted between humans through mosquito bites and, in rare cases, through contact with contaminated objects or infected bodily fluids.

Nevertheless, it is essential to remember that yellow fever is not a contagious disease like the flu or cold and can only be contracted through contact with infected materials, bodily fluids, or mosquito bites.

When a mosquito bites an infected animal or person, such as a monkey, the yellow fever virus can be transmitted to the mosquito and enter its circulation system. The virus then travels to the mosquito's salivary glands. If this infected mosquito bites another monkey or a human, the virus can enter the host's bloodstream and cause symptoms to develop.

Most individuals who contract yellow fever do not exhibit disease symptoms. In the rare event that yellow fever symptoms manifest, they tend to be relatively mild. The incubation period for yellow fever typically lasts between 3 to 6 days. This means that symptoms and signs of the disease will generally only emerge after this period has elapsed following the initial infection.

Here are some significant signs and symptoms of yellow fever (stage-wise):

It is recommended to seek medical attention and consult with a physician if you suspect that you have been exposed to yellow fever, regardless of the stage you are in.

A single virus causes yellow fever disease, but it can be categorised into two distinct forms based on its method of transmission and the environment in which it occurs. Here are the two forms of yellow fever-

Sylvatic (Jungle) Yellow Fever- Jungle yellow fever occurs in tropical rainforests and is transmitted through infected mosquitoes, usually from monkeys or other animals to humans. It can also be transmitted through contact with the bodily fluids of infected animals or humans.

This yellow fever is commonly found in some areas of South America and Africa, where humans frequently come into close contact with infected animals.

Urban Yellow Fever- Yellow fever in the urban form occurs in densely populated cities and is transmitted from one person to another through the Aedes aegypti mosquito. This mosquito often breeds in stagnant water and is commonly found in urban areas.

The disease can spread rapidly in cities with high population density and inadequate sanitation. It is believed that urban yellow fever originated from sylvatic yellow fever, as infected humans carried the virus from the jungle to metropolitan areas where the Aedes aegypti mosquito thrives.

In both kinds of yellow fever, the virus causes flu-like symptoms ranging from mild to severe. In severe cases, however, yellow fever can cause kidney failure, liver failure, and hemorrhagic fever. The most effective way to prevent yellow fever is through vaccination.

If you plan to travel to an area where yellow fever is prevalent, getting vaccinated at least ten days before your departure is essential.

Yellow fever can affect individuals of all age groups, including infants and children. Some of the most common signs and symptoms in infants and children include the following:

• High fever

• Fatigue and weakness

• Muscle pain

• Jaundice (yellowing of the eyes and skin)

• Abdominal pain

• Bleeding from the nose, eyes, and mouth

• Headache

• Nausea and vomiting

• Dark urine

• Seizures (in severe cases)

Jaundice typically occurs due to liver damage by the virus. In multiple cases, yellow fever can cause seizures which can prove to be life-threatening. You must seek immediate medical assistance if you experience any of these symptoms in your infant or child.

An early diagnosis and treatment improve the chances of recovery. In addition, taking preventive measures like avoiding exposure to mosquitoes and vaccination can also help to protect your children and infants from yellow fever.

Hence, ensuring that your child's vaccinations are up-to-date and taking preventive measures while visiting regions where yellow fever is widespread is crucial.

Not every patient progresses to the toxic phase, and some patients may undergo yellow fever treatment and completely recover after the acute phase. However, the mortality rate can be as high as 50% for patients who proceed to the toxic stage.

Thus, it is crucial to seek immediate medical assistance if you experience yellow fever symptoms.
Vaccination is the most effective way to prevent yellow fever. If you plan to travel to a region where yellow fever disease is endemic, you must get vaccinated ten days before the trip.

Yellow fever has three different stages, namely the acute stage, the remission stage, and the toxic stage. The prognosis for yellow fever patients varies based on the stage of the disease.

Acute Phase- This stage's prognosis for yellow fever patients is usually good. Most of the patients recover within 3 to 4 days. The mortality rate at this stage is low.

Remission Phase- Patients' fever typically decreases during the remission stage, and their symptoms tend to improve. Generally, the prognosis for this stage is favourable, as most patients recover fully within 10 to 14 days.

Toxic Phase- The prognosis for the patients in this phase is poor, with a mortality rate estimation ranging from 20% to 50%. Patients who progress to this phase need monitoring and intensive supportive care. Even with appropriate treatment and care, some patients may not survive.

Timely diagnosis and prompt treatment can significantly improve the prognosis for yellow fever patients, particularly those in the toxic stage. For personalised advice on yellow fever disease, it is recommended to consult with a medical expert if you have any questions.

Depending on the phase of yellow fever you are experiencing, you may or may not live. A prompt diagnosis can increase the survival chances. Getting a quick diagnosis can increase your chances of survival.

The stages of yellow fever are represented in the table below, along with the survival rate.

It is essential to note that these numbers are approximate, and the survival rate of patients may vary based on factors like overall health, age, and access to quality medical care. A timely diagnosis and prompt medical care can significantly enhance the survival chances for yellow fever patients.

Yellow fever is primarily transmitted via infected mosquito bites. Any individual who is bitten by such infected mosquitoes can contract yellow fever disease. However, some specific populations are more susceptible to yellow fever than others.

People not vaccinated against yellow fever are at an increased risk of contracting the disease. Additionally, those who live in or travel to regions where yellow fever is endemic also face a higher risk. These areas are typically located in tropical and subtropical parts of South America and Africa.

Furthermore, individuals with compromised immune systems due to specific medical conditions or heightened risks may be more susceptible to severe symptoms and infection with yellow fever. Such medical conditions include cancer, HIV/AIDS, and organ transplantation.

Yellow fever can be detected through laboratory testing, typically using a blood test to identify the virus or antibodies to the virus. A medical professional may also conduct a physical examination to check for symptoms such as headache, fever, jaundice, and muscle pain.

Additional medical tests, including viral culture, liver function tests, chest X-rays, and polymerase chain reaction (PCR) tests, may be performed to identify complications related to the disease. Seeking medical attention is crucial if exposure to the yellow fever virus is suspected.

Here are some common medical ways to detect the symptoms of yellow fever

Physical examination-** A physical examination is one of the most common ways to detect yellow fever symptoms. However, to be sure of the diagnosis, additional tests should be conducted because the symptoms can be similar to those of other diseases.

Blood tests- The yellow fever virus or antibodies to the virus can be detected through blood tests.

Liver function tests- Liver function tests are used to determine the extent of liver damage induced by yellow fever.

Viral culture- Viral culture refers to the collection of body fluid samples to test the presence of the yellow fever virus.

Polymerase Chain Reaction (PCR) test- The PCR test detects the genetic material of the yellow fever virus in a tissue sample or blood.

Chest X-ray-** Chest x-ray helps to detect any respiratory issues that may be associated with yellow fever.

You can take several steps to reduce your risk of developing yellow fever. Here are a few of them:

1. Vaccination

• Vaccination is the most common preventive measure for yellow fever. If you are travelling to a location where yellow fever exists, you must get vaccinated 10 to 14 days before departure. A single shot of the yellow fever vaccine can provide prevention for ten years, and you may be secure for life.

• Side effects may include:

• Low-grade fevers

• Tiredness

• Soreness at the injection site

• Headaches

• Some severe reactions like encephalitis can occur in rare cases among infants and older individuals.

• Muscle pain

The vaccine is considered safe for patients aged 9 months to 60 years. The following groups of people should avoid vaccination:

• Breastfeeding mothers

• Pregnant women should avoid it unless the risk is inevitable.

• People allergic to eggs

People with weakened immune systems, including those with HIV or receiving chemotherapy and radiotherapy, should avoid it unless the risk of yellow fever is unavoidable.

Any patient over 60 years should discuss with a professional whether or not to have the vaccine.

2. Protection from mosquitoes

• Experts recommend taking the following measures to reduce exposure to mosquitoes:

• It is recommended to avoid outdoor activities during dusk, dawn, and early evening hours when mosquitoes are most active.

• Staying indoors in places with good screening, such as window nets and air-conditioning, is recommended.

It is advised to apply mosquito repellent containing permethrin to clothing, shoes, bed netting, and camping equipment, but not directly on the skin.

• In areas where mosquitoes are present, wearing long-sleeved shirts and long pants is advisable to cover as much skin as possible.

3. Epidemic response and preparedness

Timely detection of yellow fever, detection of causes of yellow fever and swift response through emergency vaccination campaigns are crucial for preventing outbreaks. Nevertheless, underreporting is a cause for concern, as the actual number of cases is estimated to be 10 to 250 times higher than what is currently being reported.

It is recommended by WHO that every at-risk country should have at least one national laboratory qualified to perform basic yellow fever blood tests. An outbreak is considered to have occurred when a confirmed case of yellow fever is reported in an unvaccinated population.

In any context, a confirmed case must be thoroughly investigated, and response teams must implement emergency measures, and longer-term immunisation plans to address the outbreak.

The overlook of a yellow fever patient varies depending on the infection severity, effectiveness, and promptness of the treatment. Mild cases can show improvement within a few days with hydration, rest, and over-the-counter medicines for pain relief and fever. However, severe yellow fever cases can cause life-threatening complications, including kidney and liver failure, shock, bleeding disorders, and organ damage.

If medical intervention is not provided, severe cases of yellow fever can result in mortality rates as high as 50%. Even with adequate medical attention, the intensity of yellow fever can cause enduring effects on the patient's health and quality of life. Therefore, it is crucial to prevent exposure to the virus in areas where it is endemic, and vaccination is necessary for effectively managing yellow fever.

Yellow fever can cause severe illness and even death in some extreme cases. Yellow fever treatment can be costly, especially if hospitalisation is needed. With critical illness insurance, treatment expenses can be easily manageable. Besides the cost of treatment, prevention is also crucial for yellow fever.

Vaccination is a common preventive measure recommended to those travelling to endemic regions to protect against the illness. Some health insurance plans help cover vaccination expenses and any associated medical consultations. They provide peace of mind and ensure medical care if you contract the disease.

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