Yellow fever

The first symptoms of yellow fever usually develop 3 to 6 days after infection. They include:

• Muscle pain and backache
• Feeling sick or vomiting
• Fatigue (feeling tired)
• General body aches
• Nausea
• Severe headache
• Eyes being sensitive to light

Most people with the initial symptoms improve within one week. For some individuals, weakness and fatigue may persist for several months after recovery. Yellow fever can be deadly among those who develop severe disease. Up to 1 in 4 people may experience a more severe form of the disease with symptoms such as:

• Yellowing of the skin and eyes (jaundice)
• Organ failure
• Bleeding from the mouth, nose, eyes, or ears
• High fever
• Shock

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The yellow fever virus is an arbovirus of the flavivirus genus and is transmitted by mosquitoes, specifically Aedes and Haemogogus species. Different mosquito species inhabit various environments: some live in the wild, some are domestic, and some thrive in both habitats. There are three types of transmission cycles:

• Sylvatic (or jungle) yellow fever: In tropical rainforests, monkeys, which serve as the primary reservoir of yellow fever, are bitten by wild mosquitoes of the Aedes and Haemogogus species. These mosquitoes transmit the virus to other monkeys. Humans traveling in the forest may be bitten by infected mosquitoes and subsequently develop yellow fever.
• Intermediate yellow fever: In this transmission type, semi-domestic mosquitoes (those that breed both in the wild and around households) infect both monkeys and humans. Increased contact between people and infected mosquitoes leads to heightened transmission. This is the most common type of outbreak in Africa.
• Urban yellow fever: Large epidemics occur when infected individuals introduce the virus into densely populated areas with a high density of Aedes aegypti mosquitoes, where most people have little or no immunity due to a lack of vaccination or prior exposure to yellow fever.

• Being unvaccinated: Unvaccinated young children are prone to yellow fever and its complications, including death. Unvaccinated pregnant women and nonimmune individuals can also become infected.
• International traveling: Traveling to countries where yellow fever is prevalent and less controlled increases the risk of developing the disease.
• Countries experiencing a yellow fever outbreak: Countries undergoing or recovering from a natural disaster may have damaged health infrastructures, which interrupts routine immunization and significantly raises the risk of infection.

Yellow fever is difficult to diagnose, especially during its early stages. A more severe case can be confused with severe malaria, leptospirosis, viral hepatitis, other hemorrhagic fevers, and infection with other flaviviruses (such as dengue hemorrhagic fever).

1. History and Physical Examination

The diagnosis requires a thorough travel history and record of immunization. The doctor may evaluate the present symptoms such as:

• Headache
• Malaise
• Jaundice
• Myalgias with severe back pain

The incubation period of the virus is usually 3-7 days, with most individuals experiencing a mild flu-like illness. In severe cases (15%), symptoms may include:

• Chills
• Low back pain
• Headache
• Fever

During the physical examination, the doctor may check for:

• Faget sign or pulse fever dissociation
• Facial flushing
• Conjunctival injection

During the most toxic phase, patients may develop:

• Jaundice
• Dark urine
• Vomiting
• Bleeding from mucous membranes and in the gastrointestinal tract

2. Lab Tests

Laboratory confirmation is important after the physical evaluation is completed.

• Antigen Detection: Rapid detection methods include the detection of yellow fever antigen using a monoclonal enzyme immunoassay in serum specimens. This is accomplished by testing serum to detect virus-specific IgM and neutralizing antibodies.
• Polymerase Chain Reaction: This improved technique ensures specific detection of a wide range of yellow fever virus genotypes and may increase the sensitivity of detection.
• Enzyme-Linked Immunosorbent Assay (ELISA): This common test detects different types of antibodies produced at various stages of the infection, using the binding of antibodies to antigens to identify and measure certain substances.

3. Other Tests

• Lumbar Puncture: In cases of altered mentation, a lumbar puncture is performed. This procedure involves collecting a sample of cerebrospinal fluid (CSF).
• Computed Tomography (CT) Scan: A CT scan uses computers and rotating X-ray machines to create cross-sectional images of the body. It is performed if the brain is involved in yellow fever.
• Liver Function Tests (LFT): If the liver is involved, the coagulation profile may be abnormal.
• Chest X-ray: A chest X-ray is conducted in patients with respiratory distress due to pulmonary edema.
• Electrocardiograph (ECG): This test is performed in cases of prolonged QT and PR intervals, as arrhythmias are common when the myocardium is affected.
• Complete Blood Count (CBC): The blood test may show a reduction in the number of infection-fighting white blood cells (leucopenia), as the yellow fever virus affects the bone marrow.

The most effective way to prevent infection from the yellow fever virus is to prevent mosquito bites. Mosquitoes bite during the day and night.

Vector Control

• Use insect repellents.
• Wear long-sleeved shirts and pants.
• Stop mosquito breeding indoors and outdoors by avoiding water lodging.
• Prevent mosquito bites while traveling overseas.

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Vaccination

Yellow fever can be prevented by receiving a vaccination against it. A single injection of the yellow fever vaccine given subcutaneously provides immunity to 100% of its recipients. The vaccine provides immunity only after 10 days. However, a booster dose is required every ten years for persons residing in non-endemic countries. A further dose of the vaccine is recommended for a small number of travelers visiting yellow fever risk areas, including those who were previously vaccinated when they were:

• Pregnant
• Under 2 years old
• Living with HIV
• Had a weakened immune system

There are some groups of people who cannot receive the yellow fever vaccine when it is recommended, including:

• People whose immune systems are weakened by treatment, such as steroids and chemotherapy.
• People who had a severe reaction to a previous dose of the yellow fever vaccine.
• People with a thymus gland disorder or who have had their thymus gland removed.

Epidemic Preparedness and Response

Prompt detection of yellow fever and rapid response through emergency vaccination campaigns are essential for controlling outbreaks. A confirmed case of yellow fever in an unvaccinated population is considered an outbreak. A confirmed case in any context must be fully investigated.

There is no specific treatment for yellow fever, but severe cases require aggressive supportive care. Hydration can be helpful in providing relief:

• Rest, drink fluids, and use pain relievers and medications to reduce fever and relieve aches.
• Avoid certain medications, such as aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or naproxen, which may increase the risk of bleeding.
• People with severe symptoms of yellow fever infection should be hospitalized for close observation and supportive care.
• Individuals with yellow fever should be protected from further mosquito exposure, such as staying indoors or under a mosquito net, during the first few days of illness to prevent contributing to the disease transmission cycle.
• Paracetamol and ibuprofen can be taken to control fever and alleviate pain caused by the virus; for children, liquid paracetamol can be used.
• If a person has a high temperature, increase fluid intake to reduce the risk of dehydration.

No specific treatment exists for yellow fever, which is one reason that preventative measures such as vaccination are so important. Supportive treatment is aimed at controlling the symptoms and includes rest, fluids, and the use of medicines to help relieve fever and aches. There is no specific home care treatment for yellow fever. The patient requires care, periodic medicines, and some precautions. Home care is essential to make the disease more tolerable:

• Get plenty of rest.
• A sponge bath can reduce discomfort due to fever.
• Drink plenty of water.
• Use pain relievers and analgesics such as acetaminophen.
• To reduce itching from the rash, apply witch hazel to the rashes or add oatmeal to a bath.
• Communicate openly with a doctor regarding any questions related to the disease.
• Ensure adequate sleep.
• Make dietary modifications.
• Drink a minimum of 8 glasses of water daily.
• Avoid refined foods, such as white bread, pasta, and sugar.
• Use healthy oils in cooking, such as olive oil, coconut oil, or ghee.
• Reduce or eliminate trans fats found in processed and packaged foods like biscuits, namkeens, and cakes.
• Limit caffeine-containing beverages like coffee. Avoid alcohol and tobacco.

Home Remedies

The following home remedies can help in recovery from yellow fever:

• Garlic (Lehsun): Known for its anti-inflammatory properties, it is an effective remedy for mosquito bites.
• Tomato (Tamatar): A good source of water content, it helps provide hydration and relief from nausea or vomiting caused by yellow fever.
• Coconut water (Nariyal pani): An excellent supplement for yellow fever, it can help restore normal eye color.
• Watermelon (Tarbuz): With cooling properties, it is a great substitute for fluids lost due to nausea, vomiting, or appetite loss during yellow fever.
• Bitter gourd (Karela): Effective in reducing inflammation, it is advisable to drink at least two tablespoons of bitter gourd juice twice a day.