Symptoms
Yellow fever symptoms usually appear 3-6 days after infection. Initial symptoms include:
Fever
Headache
Muscle aches (especially in the back)
Nausea
Vomiting
Loss of appetite
Dizziness
Red eyes, face or tongue In severe cases, symptoms can progress to:
Jaundice (yellowing of the skin and eyes)
Bleeding (from the mouth, nose, eyes, or stomach)
Black vomit (due to digested blood)
Kidney failure
Liver failure
Shock
Multi-organ failure
Causes
Yellow fever is caused by the yellow fever virus, which is transmitted to humans through the bite of infected mosquitoes. Specifically, Aedes and *Haemagogus* mosquito species are the primary vectors. The virus multiplies in the mosquito, and when the mosquito bites a human, the virus enters the bloodstream.
Medicine Used
There is no specific antiviral medication to cure yellow fever. Treatment focuses on managing symptoms and preventing complications. This includes:
Rest
Fluids (to prevent dehydration)
Pain relievers (such as acetaminophen for fever and muscle aches – avoid aspirin and other NSAIDs due to the risk of bleeding)
Medications to manage nausea and vomiting
Blood transfusions (if needed, to address bleeding)
Kidney dialysis (if kidney failure develops)
Support for liver failure.
Management of secondary infections.
Is Communicable
Yellow fever itself is not directly communicable from person to person through casual contact. It is transmitted through the bite of an infected mosquito. If a mosquito bites a person infected with yellow fever, that mosquito can then transmit the virus to another person.
Precautions
The most important precaution is vaccination. Other precautions include:
Vaccination: Get vaccinated against yellow fever if traveling to areas where the disease is present.
Mosquito repellent: Use insect repellent containing DEET, picaridin, IR3535, or oil of lemon eucalyptus.
Protective clothing: Wear long sleeves, long pants, and socks when outdoors, especially during peak mosquito activity times (dawn and dusk).
Mosquito nets: Sleep under mosquito nets, especially if your accommodations are not air-conditioned or screened.
Eliminate mosquito breeding grounds: Reduce standing water around your home and in your community (e.g., in tires, flower pots, buckets).
Stay indoors: During peak mosquito activity times.
How long does an outbreak last?
The duration of a yellow fever outbreak can vary depending on several factors, including:
Vaccination coverage: High vaccination rates can quickly halt an outbreak.
Mosquito control measures: Effective mosquito control efforts can limit transmission.
Geographic area: Outbreaks in densely populated areas may be more difficult to control.
Environmental conditions: Rainfall, temperature, and other environmental factors can affect mosquito populations and virus transmission. Outbreaks can last from a few weeks to several months or even longer if control measures are not implemented effectively.
How is it diagnosed?
Yellow fever is diagnosed based on a combination of factors:
Symptoms: Clinical presentation of fever, jaundice, bleeding, etc.
Travel history: Recent travel to or residence in an area where yellow fever is endemic.
Laboratory tests:
Blood tests: To detect the presence of the yellow fever virus or antibodies produced by the body in response to the virus.
RT-PCR: To detect viral RNA
ELISA: To detect IgM or IgG antibodies
Virus neutralization test (PRNT): Highly specific confirmatory test
Liver function tests: To assess liver damage.
Kidney function tests: To assess kidney damage.
Other tests: To rule out other diseases that can cause similar symptoms (e.g., malaria, dengue fever, leptospirosis).
Timeline of Symptoms
The typical timeline of yellow fever symptoms:
Incubation period: 3-6 days (no symptoms)
Initial phase (acute phase): 3-4 days
Sudden onset of fever, headache, muscle aches, nausea, vomiting, dizziness.
Remission phase (brief): 1-2 days
Symptoms may temporarily subside.
Toxic phase (severe cases):
Jaundice, bleeding, black vomit, kidney failure, liver failure, shock, multi-organ failure.
This phase can be fatal. Not all individuals progress to the toxic phase. Some may only experience the initial phase and then recover.
Important Considerations
Vaccination is crucial: Yellow fever vaccine is highly effective and provides lifelong immunity in most people.
Vaccine adverse events: While rare, the yellow fever vaccine can cause serious adverse events, particularly in those with weakened immune systems, older adults, and infants. Risks and benefits of vaccination should be discussed with a healthcare provider.
Supportive care: Early supportive care is essential for managing symptoms and preventing complications.
Reporting: Yellow fever is a reportable disease. Suspected cases should be reported to public health authorities.
Travel advisories: Check travel advisories before traveling to areas where yellow fever is present.
Aspirin and NSAIDs: Avoid aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) due to the risk of bleeding.
Pregnant or breastfeeding women: Vaccination considerations should be discussed with a healthcare provider.
Mosquito control: Continue to practice mosquito bite prevention measures even if vaccinated.
Vaccination not always possible There are instances of medical conditions and age where you cannot have the vaccine. Consult your doctor for advice.