Yellow Fever

Mosquito

What is Yellow Fever

Yellow fever is an acute viral haemorrhagic disease transmitted by infected mosquitoes. Yellow fever virus (YFV) is a single-stranded RNA virus that belongs to the genus Flavivirus. The “yellow” in the name refers to the jaundice that affects some patients. The virus is endemic in tropical areas of Africa and Latin America, with a combined population of over 900 million people.

Signs and Symptoms of Yellow Fever

Once contracted, the virus incubates in the body for 3 to 6 days, followed by infection that can occur in one or two phases.

  1. The first, “acute”, phase usually causes :-
  • Fever
  • Muscle pain with prominent backache, headache, shivers, loss of appetite, and nausea or vomiting.
  • Most patients improve and their symptoms disappear after 3 to 4 days.
  1. About 15% of patients enter a second, more toxic phase within 24 hours of the initial remission.

    Yellow Fever Transmission
  • High fever returns
  • Several body systems are affected
  • The patient rapidly develops jaundice and complains of abdominal pain with vomiting.
  • Bleeding can occur from the mouth, nose, eyes or stomach. Once this happens, blood appears in the vomit and fasces.
  • Kidney function deteriorates.
  • Half of the patients who enter the toxic phase die within 10 to 14 days, the rest recover without significant organ damage.

Transmission of Yellow Fever

The yellow fever virus is an arbovirus of the flavivirus genus, and the mosquito is the primary vector. It carries the virus from one host to another, primarily between monkeys, from monkeys to humans, and from person to person. Several different species of the Aedes and Haemogogus mosquitoes transmit the virus. The mosquitoes either breed around houses (domestic), in the jungle (wild) or in both habitats (semi-domestic). There are three types of transmission cycles.

Treatment of Yellow Fever

There is no specific treatment for yellow fever, only supportive care to treat dehydration, respiratory failure and fever. Associated bacterial infections can be treated with antibiotics. Supportive care may improve outcomes for seriously ill patients, but it is rarely available in poorer areas.

Prevention of Yellow Fever

  • Vaccination is the single most important measure for preventing yellow fever. The yellow fever vaccine is safe and affordable, providing effective immunity against yellow fever within 10 days for 80–100% of people and 99% immunity within 30 days. A single dose of yellow fever vaccine is sufficient to confer sustained immunity and life-long protection against yellow fever disease and a booster dose of yellow fever vaccine is not needed. Serious side effects are extremely rare.
  • Mosquito control is vital until vaccination takes effect. The risk of yellow fever transmission in urban areas can be reduced by eliminating potential mosquito breeding sites and applying insecticides to water where they develop in their earliest stages
  • Travelers should get vaccinated for yellow fever before visiting areas where yellow fever is found.
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