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Yellow Fever

Updated : November 22, 2022





Background

Yellow fever is a viral disease spread by mosquitoes in tropical and subtropical regions of Africa and South America. The mosquito species Aedes and Haemagogus are the primary carriers of the disease. It can manifest clinically, from a minor, self-limiting febrile sickness to a severe hemorrhage and liver damage.

The yellow color results from jaundice, which some individuals with severe disease retain. Travel history to an endemic region, contact with infected mosquitoes, prior immunization history, symptoms, and laboratory results are used to identify the illness.

Most cases are self-limiting and mimic other widespread viral illnesses. The best strategy to avoid getting the virus is to avoid mosquito bites, aside from vaccination.

Epidemiology

Yellow fever epidemics have diminished due to vaccination, but the disease has reappeared in many regions of Africa and South America. Yellow fever affects people of all ages and races. Infants and the elderly frequently have weakened immune systems and are estimated to have the highest fatality rates.

In the US, yellow fever is relatively uncommon. Most infections are discovered among unvaccinated visitors to South America or sub-Saharan Africa. In comparison, most individuals experience a self-limited infection, and some experience severe illness.

Anatomy

Pathophysiology

There is a 3-to-6-day incubation period. Once contracted, the virus spreads rapidly to other organs. The most significant organ impacted by yellow fever is the liver. As a result of liver damage, it causes severe jaundice. Similar degenerative changes can also occur in the kidneys, resulting in acute renal failure.

When the upper GI tract is implicated, the combination of stomach acid and blood causes black vomit. Cerebral edema and bleeding are characteristics of the central nervous system. Another typical manifestation of yellow fever is encephalopathy.

Etiology

It is an RNA virus of the genus Flavivirus and exhibits similarities with the viruses that induce St. Louis, Japanese encephalitis, and West Nile. During monsoon, mosquitoes that breed in tree hollows, like Haemagogous and Aedes aegypti, spread yellow fever. The yellow fever virus has three transmission cycles—jungle, urban and intermediate.

Transmission between non-human primates and mosquitoes occurs during the jungle cycle. Infected mosquito bites can infect humans when traveling to or working in the forest. Humans that reside in or work in jungle border areas are a part of the intermediate cycle, which takes place in the African savannah.

Humans and monkeys may contract diseases from each other or via mosquitoes. In the urban cycle, a human with the virus bears to an urban setting after contracting it in either the intermediate or jungle cycle. No human-to-human or primate-to-human transmission cases have been documented without a mosquito vector.

Genetics

Prognostic Factors

Most patients have a favorable prognosis and are asymptomatic or moderately symptomatic. 1 in 15 people with symptoms will progress to a severe condition. While most will recover, a full recovery from yellow fever may take weeks or months. The abnormality of the liver and kidneys usually reverse.

In individuals with severe illness, death occurs in 30% to 50% of cases. All visitors to endemic regions should get vaccinated if they are eligible for the live attenuated vaccine. Death commonly occurs within two weeks during the toxic phase of the infection.

When visiting endemic regions, unvaccinated tourists run a higher chance of contracting symptoms than locals, who have built up immunity. Following vaccination, a few isolated neurologic and viscerotropic incidences have been documented.

Clinical History

Physical Examination

Age group

Associated comorbidity

Associated activity

Acuity of presentation

Differential Diagnoses

Laboratory Studies

Imaging Studies

Procedures

Histologic Findings

Staging

Treatment Paradigm

by Stage

by Modality

Chemotherapy

Radiation Therapy

Surgical Interventions

Hormone Therapy

Immunotherapy

Hyperthermia

Photodynamic Therapy

Stem Cell Transplant

Targeted Therapy

Palliative Care

Medication

 

yellow fever vaccine 

Prophylaxis: 0.5ml subcutaneous administered for more than ten days before the travel

Additional/booster dosage for high-risk populations

For most visitors, a single primary dosage of the yellow fever vaccine is sufficient and offers long-lasting protection.

Yellow fever immunization booster shots are advised for:
Before their subsequent trip that places them at risk for yellow fever viral infection, women who received their first yellow fever vaccine while expectant (independent of gestation) should receive one extra dose.

Before the subsequent trip that places them at risk for yellow fever virus infection, people who had a hematopoietic stem cell donation after getting a dosage of the yellow fever vaccine and who are immunocompetent enough to be securely immunized should get vaccinated again. Disease or hepatitis C, to protect against further liver damage.

High-risk booster after ten years
Travelers who got their last yellow fever vaccine at least ten years ago and will be in a higher-risk setting due to season, area, activities, and length may obtain a repeat.
HIV-positive people should get a yellow fever vaccine every ten years.
Travelers who plan to stay in endemic areas for a long time or in highly endemic areas like rural West Africa during peak transmission season or an epidemic area



 

yellow fever vaccine 

>6 months (off-label): 0.5 mL subcutaneous of 1 dose more than ten days before the travel
>9 months: 0.5 mL subcutaneous of 1 dose more than 10 days before the travel

Additional/booster dosage for high-risk populations

For most visitors, a single primary dosage of the yellow fever vaccine is sufficient and offers long-lasting protection.
yellow fever immunization booster shots are advised for

Before the subsequent trip that places them at risk for yellow fever virus infection, people who had a hematopoietic stem cell donation after getting a dosage of the yellow fever vaccine and who are immunocompetent enough to be securely immunized should get vaccinated again.
Booster dosage for high-risk patients after ten years Travelers who got their last dosage of the yellow fever vaccine at least ten years ago and will be in a higher-risk area based on the season, location, activities, and length of their trip may be given a supplemental dose. yellow fever vaccination should be given every ten years to people who were HIV positive when they got their last dosage. Those who journey to highly endemic regions like rural West Africa during the height of transmission season or a region where an epidemic is still active or who intend to spend a significant amount of time there



 

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References

https://www.ncbi.nlm.nih.gov/books/NBK470425/

Yellow Fever

Updated : November 22, 2022




Yellow fever is a viral disease spread by mosquitoes in tropical and subtropical regions of Africa and South America. The mosquito species Aedes and Haemagogus are the primary carriers of the disease. It can manifest clinically, from a minor, self-limiting febrile sickness to a severe hemorrhage and liver damage.

The yellow color results from jaundice, which some individuals with severe disease retain. Travel history to an endemic region, contact with infected mosquitoes, prior immunization history, symptoms, and laboratory results are used to identify the illness.

Most cases are self-limiting and mimic other widespread viral illnesses. The best strategy to avoid getting the virus is to avoid mosquito bites, aside from vaccination.

Yellow fever epidemics have diminished due to vaccination, but the disease has reappeared in many regions of Africa and South America. Yellow fever affects people of all ages and races. Infants and the elderly frequently have weakened immune systems and are estimated to have the highest fatality rates.

In the US, yellow fever is relatively uncommon. Most infections are discovered among unvaccinated visitors to South America or sub-Saharan Africa. In comparison, most individuals experience a self-limited infection, and some experience severe illness.

There is a 3-to-6-day incubation period. Once contracted, the virus spreads rapidly to other organs. The most significant organ impacted by yellow fever is the liver. As a result of liver damage, it causes severe jaundice. Similar degenerative changes can also occur in the kidneys, resulting in acute renal failure.

When the upper GI tract is implicated, the combination of stomach acid and blood causes black vomit. Cerebral edema and bleeding are characteristics of the central nervous system. Another typical manifestation of yellow fever is encephalopathy.

It is an RNA virus of the genus Flavivirus and exhibits similarities with the viruses that induce St. Louis, Japanese encephalitis, and West Nile. During monsoon, mosquitoes that breed in tree hollows, like Haemagogous and Aedes aegypti, spread yellow fever. The yellow fever virus has three transmission cycles—jungle, urban and intermediate.

Transmission between non-human primates and mosquitoes occurs during the jungle cycle. Infected mosquito bites can infect humans when traveling to or working in the forest. Humans that reside in or work in jungle border areas are a part of the intermediate cycle, which takes place in the African savannah.

Humans and monkeys may contract diseases from each other or via mosquitoes. In the urban cycle, a human with the virus bears to an urban setting after contracting it in either the intermediate or jungle cycle. No human-to-human or primate-to-human transmission cases have been documented without a mosquito vector.

Most patients have a favorable prognosis and are asymptomatic or moderately symptomatic. 1 in 15 people with symptoms will progress to a severe condition. While most will recover, a full recovery from yellow fever may take weeks or months. The abnormality of the liver and kidneys usually reverse.

In individuals with severe illness, death occurs in 30% to 50% of cases. All visitors to endemic regions should get vaccinated if they are eligible for the live attenuated vaccine. Death commonly occurs within two weeks during the toxic phase of the infection.

When visiting endemic regions, unvaccinated tourists run a higher chance of contracting symptoms than locals, who have built up immunity. Following vaccination, a few isolated neurologic and viscerotropic incidences have been documented.

yellow fever vaccine 

Prophylaxis: 0.5ml subcutaneous administered for more than ten days before the travel

Additional/booster dosage for high-risk populations

For most visitors, a single primary dosage of the yellow fever vaccine is sufficient and offers long-lasting protection.

Yellow fever immunization booster shots are advised for:
Before their subsequent trip that places them at risk for yellow fever viral infection, women who received their first yellow fever vaccine while expectant (independent of gestation) should receive one extra dose.

Before the subsequent trip that places them at risk for yellow fever virus infection, people who had a hematopoietic stem cell donation after getting a dosage of the yellow fever vaccine and who are immunocompetent enough to be securely immunized should get vaccinated again. Disease or hepatitis C, to protect against further liver damage.

High-risk booster after ten years
Travelers who got their last yellow fever vaccine at least ten years ago and will be in a higher-risk setting due to season, area, activities, and length may obtain a repeat.
HIV-positive people should get a yellow fever vaccine every ten years.
Travelers who plan to stay in endemic areas for a long time or in highly endemic areas like rural West Africa during peak transmission season or an epidemic area



yellow fever vaccine 

>6 months (off-label): 0.5 mL subcutaneous of 1 dose more than ten days before the travel
>9 months: 0.5 mL subcutaneous of 1 dose more than 10 days before the travel

Additional/booster dosage for high-risk populations

For most visitors, a single primary dosage of the yellow fever vaccine is sufficient and offers long-lasting protection.
yellow fever immunization booster shots are advised for

Before the subsequent trip that places them at risk for yellow fever virus infection, people who had a hematopoietic stem cell donation after getting a dosage of the yellow fever vaccine and who are immunocompetent enough to be securely immunized should get vaccinated again.
Booster dosage for high-risk patients after ten years Travelers who got their last dosage of the yellow fever vaccine at least ten years ago and will be in a higher-risk area based on the season, location, activities, and length of their trip may be given a supplemental dose. yellow fever vaccination should be given every ten years to people who were HIV positive when they got their last dosage. Those who journey to highly endemic regions like rural West Africa during the height of transmission season or a region where an epidemic is still active or who intend to spend a significant amount of time there



https://www.ncbi.nlm.nih.gov/books/NBK470425/